Solution processing and properties of functional oxide thin films and nanostructures-III

Resume : We are moving towards a sustainable society powered by renewal energy where solar photovoltaics is one of the most important players. In the past few years, emerging photovoltaic (PV) technologies have observed an exponential increase in power conversion efficiencies (PCE) with halide perovskite solar cells above 22 %, tandem photovoltaics reaching 24 % or dye sensitized solar cells for indoor lighting at the impressive 28.9 % PCE mark. These technologies could potentially complement the commercial Silicon solar cells if they uphold current low costs and long-lifetimes of 25 years. Oxides in solar cells can be found as the main solar absorber responsible for photon-to-electron conversion, as interfacial layers for the transport of electron or holes, as part of the conductive metal electrodes (including transparent electrodes) and also as part of photon management. Their main advantage is the ease of fabrication, low cost and enhanced stability provided to the solar cell. They can also contribute to advantages still not found in commercial PVs like flexibility, transparency or low weight. Moreover, new-generation of oxides (e.g. ternary, ferroelectric, etc.) are slowly breaking ground providing competitive power conversion efficiencies, enhanced transport properties or improved UV-light stability. In this presentation we show the application of binary and complex oxides in emerging photovoltaics. We specifically discuss about the application of oxides applied as barrier layers or as light absorbers in next-generation solar cell technologies such as organic, dye sensitized, halide perovskite, tandem solar cells and all-oxide solar cells. We will show the most recent results obtained in our laboratory for the application of these oxides in solar cells.1-2 [1] M. Lira-Cantú, Perovskite solar cells: Stability lies at interfaces, Nature Energy, 2 (2017) nenergy2017115. [2] M. Lira-Cantu, The future of semiconductor oxides in next generation solar cells, 1st ed., Elsevier, 2017.

Resume : During last few years, Perovskite solar cells have shown a great potential both in the rapid efficiency improvement and in cheap material and production costs. The perovskite solar cell (PSC) is composed by an active layer, which is contacted with an n-type material for electron extraction (ETL - Electron Transporting Layer) and a p-type material for hole extraction. We prepared and characterized an n-type compact TiO2 and SnO2 transparent semiconductor thin film (15-20 nm) by different techniques to promote a better interface quality and improve the electron transfer to the front contact in the aim of defining the optimal configuration for the PSC realisation. The thin layers were deposited by Atomic Layer Deposition (ALD), Spray Pyrolysis Deposition (SPD) and sputtering (SPG). In addition to it, we modified the conductivity of the ETL using a Ti-Sn mixed sol-gel solution as TiO2?SnO2 precursors deposited by spin-coating (SPC). The analysis of morphology, performed through SEM and AFM, resulted in different homogeneities, thickness control and an improved conformability for SPG and ALD layers. An improved transparency in the visible region was also obtained for the latter and reported by UV-Vis spectroscopy. Interestingly, the presence of Sn in the layer improved the T% by a relative 10%. Different bandgap values, varying as function of the processing technique, were measured through Tauc plot and ellipsometry. The results of XRD patterns corresponded to the anatase phase for TiO2 and the casserite phase for SnO2. Lastly, the processed ETLs were investigated through Dark Lock-In Thermography (DLIT) to locally identify pin-holes giving rise to shunts in the layer.

Resume : The properties of a low cost transparent conducting oxide (TCO) spray pyrolysis grown ZnO thin films doped with indium have been investigated. We analyse the optical, electrical, and crystallographic properties as function of In content with a specific focus on post-growth heat treatment of these thin films at 320?C in an inert, nitrogen atmosphere, which improves the films electrical properties by a remarkable amount. The effect was found to be dominated by nitrogen induced grain boundary passivation, identified by a combined study using in-situ resistance measurement upon annealing, X-ray photoelectron spectroscopy, photoluminescence and X-ray diffraction studies. We also highlight the chemical mechanism of morphologic and crystallographic changes found in films with high indium content. In optimized growth and postannealing conditions, ZnO:In with a resistivity as low as 2×10?3 ?cm and high optical quality has been obtained using low cost spray pyrolysis.

Resume : Mg-doping of ZnO increases the band gap linearly as a function of dopant concentration. This behavior is desired for a wide range of applications, like sensors, solar cells, optoelectronic devices. Zn1-xMgxO films are commonly prepared by vacuum deposition methods (PLD, ALD, sputtering). To lower equipment costs, solution-based methods that are upscalable and yield high quality films are particularly attractive. Spray pyrolysis (SP) is a technique that fulfills these criteria. Zn1-xMgxO films deposited by SP have been reported, but often high temperatures, toxic/flammable solvents or only low dopant concentrations were employed. We present Mg-doped ZnO nanorods and compact films deposited by SP from water-based solutions at low-temperature and atmospheric conditions. The influence of Mg on the film growth and properties was investigated in detail for Mg concentration in the film up to 16 mol%. It was observed that, depending on the solution composition and deposition parameters, nanorods or compact films can be deposited. This behavior was explained in detail and the findings were used to control the film thickness and the length of nanorods. In order to show the versatility of these films or nanostructures in future applications, Zn1-xMgxO was sprayed onto transparent conducting oxide substrates, commonly used in various devices. Solar cells were fabricated and characterized in particular.

Resume : In this study, we report the transformation of the electronic defect states by performing several annealing experiments on the same samples. To this end, AZO films on the soda lime glass substrates were deposited by using sol-gel spin coating process and then subjected to various annealing conditions at different pressures. The electronic defect state analysis along with microstructure and optoelectronic properties of these films after each annealing stage were investigated by using a wide range of experimental techniques. Whereas the overall optical transmittance of all these films were changing marginally, the electronic defect states were altered significantly because of these repetitive annealing, leading to changes in the electrical properties and optical bandgap. The AZO films annealed under atmospheric pressure were found to contain deep donor level defects. Further annealing of these samples at reduced pressure and high temperature leads to higher Al doping in Zinc lattice sites, subsequently enhancing the formation of shallow donor level defects. However, in case of annealing under low vacuum only shallow donor level defects were formed, the concentration of which were found to enhance when these films were annealed for the second time under high vacuum due to enhanced Al doping. This led an increase in the carrier concentration and optical bandgap for all these films. Hence, this study throws light towards designing materials with tunable electronic defect states to have adequate optoelectronic properties at a reduced cost.

Resume : This paper focuses on quantifying the effect of an external magnetic field on the electrodeposition of ZnO nanowires and specifies a design for a nanogenerator using ZnO Nanowires and Carbon Nanotubes. A magnetic field is seen to affect the orientation of the rods grown in solution. The nanowires grown had thicknesses between 250-400 nm and were 1-2 microns long. On glass substrates and polymeric substrates, they were found to grow best with a molar ratio of 1:10 zinc nitrate to potassium chloride. The optimal temperature was found to be 70?C, optimal voltage 1 V and the pH was found to be 4.5. The SEM images have shown a significant effect of molar ratio and saturation of solution as well. Carbon nanotubes were spin coated onto the ZnO nanowires which increased the output voltage of the nanogenerator from 1V (in a AlN based system) to 1.8V. The device behaves as a piezoelectric crystal and can be used to convert sound to electricity which may then be stored in a capacitor for future use. One application of this device is as an auxiliary power producing unit in automobiles to utilize mechanical energy from vibrational losses.

Resume : Mesoporous oxide films filled with metallic nanoparticles has been widely used to enhance photocatalytic properties by reducing charge recombination. Under the effect of light, the contact between metallic NPs and oxide semiconductor could lead to different phenomena, from PICS (Plasmon Induced Charge Separation) to co-catalysis or photochromism process. To study and distinguish these mechanisms, we chose to study nanostructured electrodes made of Ag NPs inside a mesoporous semi-conductor oxide (TiO2 or Fe2O3). We performed electrochemical experiments in a three electrode configuration under various ranges of irradiation, from UV to visible, to determine the variations of redox potentials and photocurrent and thus getting insights on the photochemical mechanism and material structure influence. We demonstrate the importance of illumination on mesoporous film TiO2-Ag electrochemical properties. Light absorption not only induces a photocurrent but also modifies the reduction potential of silver NPs: A positive shift of 0.2V is observed under visible irradiation, corresponding to a modified reactivity from silver NPs within TiO2 porous matrice. This modification has been associated to a PICS process, with an electron transfer from silver NPs to TiO2 conduction band. Silver NPs are also modified due to diffusion and electrochemical Ostwald ripening during photoelectrochemical experiments. These two phenomena are more or less pronounced depending on the wavelength and the porosity, and lead to a decrease of intensity of the redox peak of silver. This presentation will also emphasize comparison between oxides matrices in terms of both synthesis and photoelectrochemical reactivity with or without silver NPs.

Resume : The design of stable visible-light absorbers and catalysts for converting H2O and CO2 into value-added chemicals poses new challenges for chemists and material scientists. Here, the ability to tailor-make material platforms with tunable morphological characteristics in an unrestricted compositional range is critical for providing understanding of the performance sensitivities to different structural parameters. Our work highlights how colloidal chemistry can aid to construct materials and to develop new concepts for storing energy into chemical bonds. [1-6] In this talk, after a general introduction on colloidal chemistry, I will give an overview on our most recent works on BiVO4/metal oxide heterostructured photoanodes and an on our nanocrystal-seeded growth approach to Sb-alloyed BiVO4 and to Cu2V2O7 with in-situ X-Ray diffraction studies elucidating the growth mechanism. [2,6] References [1] J. Lynch, C. Giannini, J. K. Cooper, A. Loiudice, I. D. Sharp, R. Buonsanti J. Phys. Chem. C 2015, 119, 7443. [2] A. Loiudice, J. Ma, W. S. Drisdell, T. M. Mattox, J. K. Cooper, T. Thao, C. Giannini, J. Yano, L.-W. Wang, I. D. Sharp, R. Buonsanti Adv. Mater. 2015, 27, 6733. [3] A. Loiudice, J.K. Cooper, Lucas H. Hess, T.M. Mattox, I.D. Sharp, R. Buonsanti Nano. Lett. 2015, 15, 7347. [4] A. Loiudice, P. Lobaccaro, E.A. Kamali, T. Thao, B.H. Hung, J.W. Ager, R. Buonsanti Angew. Chem. Int. Ed. 2016, 55, 5789. [5] C. Gadiyar, A. Loiudice, R. Buonsanti, J. Appl. Phys. D . 2017, 50, 074006. [6] C. Gadiyar, M. Strach, R. Buonsanti, submitted.

Resume : Passivation of silicon surface is an important aspect in enhancing solar cell efficiency by reducing minority carrier recombination at surface defects. Also, it is required to develop stable and high-quality passivation layers using robust and cost-effective methods to make the solar cells economical more viable. Cerium oxide (CeO2) layers were developed by spin-coating on p-Si substrate and sintered at different annealing temperatures in the range, 400-900 oC. The layers showed excellent passivation characteristics with a minority carrier lifetime, ?eff of 128 ?s in the as-grown state and ?eff improved to 374 ?s with a short hydrogen annealing at 420 oC. The observed ?eff is close to the bulk lifetime, 500 ?s. The interfacial characteristics of CeO2/Si were studied using capacitance-voltage and current-voltage measurements by evaluating flat-band voltage (VFB), interface defect density (Dit), fixed charge density (Qeff), etc. The Dit was found to be 4.7x1011 eV-1cm-2 at annealing temperature of 400 oC. Flat-band voltage (VFB) values changed from 0.65 V to 2.1 V when the annealing temperature varied from 400 oC to 700 oC, revealing the presence of negative fixed charges in the layers. The leakage current density was found to be as low as 1.04x10-7 A/cm2. The layers showed cubic structure of CeO2 with the predominant orientation of (111) and were nanocrystalline in nature. The layers have shown strong photoluminescence at the wavelengths of 574 nm, 622 nm and 675 nm above the annealing temperatures of 600 oC, and intensity of which enhanced remarkably at the higher annealing temperatures, indicating the reduction of non-radiative transitions. The luminescent characteristic of the layer would enhance blue response of the cell. The layers are highly transparent, > 90 % with an optical band gap of 3.6 eV and a refractive index of 2.6.

Resume : Fabrication of high-efficiency solar cell requires low-thermal budget processes in order to protect the electronic quality of silicon substrate that results in high minority carrier lifetime. In this report, a procedure to achieve a very high level of surface passivation for silicon wafers at low-thermal budget is elaborated. Electro- chemical oxidation of silicon was used to grow silicon di-oxide (SiO2) layers at room-temperature. Growth kinetics of SiO2 layers was investigated at a constant source voltage for different time intervals. Evolution of thickness of oxide layer was studied using spectroscopic ellipsometry, and a maximum thickness of ~ 60 nm was observed in 180 min. Passivation characteristics of SiO2 layers was investigated using minority carrier lifetime (?eff) measurements. The highest quality of surface passivation was obtained for the SiO2 layers grown for a duration of 15 min, for which ?eff is found to be 278 µs with a surface recombination velocity of 37 cm/s and an implied open-circuit voltage (iVoc) of 622 mV after a short hydrogen treatment at 400 oC that corresponds to contact annealing process. The SiO2 layer showed an improvement of 20 mV in open-circuit voltage of the solar cell device, implying the effectiveness of the passivation layer. Interface of SiO2/Si was characterized using capacitance and conductance measurements.

Resume : The field of high entropy oxides (HEOs) is very new, however, they have achieved significant research interest since their discovery. Several compositions along with different crystal structures have been already reported for HEOs [1?3]. The presence of multiple elements (5 or more) in equiatomic amounts not only helps to increase the configurational entropy of the system, which stabilizes the single phase solid solution in HEOs, but also provides the option to tailor the functional properties of the compound [4,5]. In the transition metal based high entropy oxide,((Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O here after called as TM-HEO, high room temperature Li-ion conductivity has been reported [4]. Since, Li incorporation into a TM-HEO host lattice is possible [4], it is very promising to investigate possible Li storage mechanisms and related electrochemical behavior of the TM-HEOs. In this study TM-HEOs were used as electrode materials for secondary Li-ion batteries. The TM-HEOs were synthesised by nebulized spray pyrolysis method. The resulting oxide particles had a broad size distribution containing both hollow and filled spheres. High capacities (above 500 mAh g-1) along with substantial stability (over 250 cycles) were observed when the TM-HEOs were cycled against Li as counter electrode. With in-operando X-ray diffraction (XRD) and transmission electron microscopy measurements (TEM) we were able to retrace the electrochemical reactions of the TM-HEO, and to describe the related structural changes observed during the redox processes. A conversion based mechanism was observed, with a partial conversion of some of the constituent cations keeping the host structure intact during the complete cycling process. A stabilization effect regarding the capacity retention could be shown which is related to the high configuration entropy of the TM-HEO. Furthermore, the study also shows that the usage of TM-HEO as a potential electrode material provides a unique possibility to fine-tune important electrochemical properties just by changing its chemical composition, which is often not possible with conventional electrode materials. This very initial study on TM-HEO as potential candidates for reversible Li storage can open up new areas of application for these kind of electrode materials and, hopefully, will initiate further investigations on HEO materials for primary and secondary batteries. References: [1] C.M. Rost, E. Sachet, T. Borman, A. Moballegh, E.C. Dickey, D. Hou, J.L. Jones, S. Curtarolo, J.-P. Maria, Entropy-stabilized oxides, Nat. Commun. 6 (2015) 8485. doi:10.1038/ncomms9485. [2] A. Sarkar, C. Loho, L. Velasco, T. Thomas, S.S. Bhattacharya, H. Hahn, R. Djenadic, Multicomponent equiatomic rare earth oxides with a narrow band gap and associated praseodymium multivalency, Dalt. Trans. 46 (2017) 12167?12176. doi:10.1039/C7DT02077E. [3] A. Sarkar, R. Djenadic, D. Wang, C. Hein, R. Kautenburger, O. Clemens, H. Hahn, Rare earth and transition metal based entropy stabilised perovskite type oxides, J. Eur. Ceram. Soc. (2017) 0?1. doi:10.1016/j.jeurceramsoc.2017.12.058. [4] D. Bérardan, S. Franger, A.K. Meena, N. Dragoe, Room temperature lithium superionic conductivity in high entropy oxides, J. Mater. Chem. A. 4 (2016) 9536?9541. doi:10.1039/C6TA03249D. [5] D. Bérardan, S. Franger, D. Dragoe, A.K. Meena, N. Dragoe, Colossal dielectric constant in high entropy oxides, Phys. Status Solidi - Rapid Res. Lett. 10 (2016) 328?333. doi:10.1002/pssr.201600043.

Resume : While a great research effort is currently being invested in sodium ion batteries (NIBs), their performance is still inferior to that of lithium ion batteries (LIBs). The low stability of NIB materials during battery operation is one of the main challenges to tackle. Here, we report a novel anode material with an excellent stability and capacity synthesized via the solution gel route. The material was characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. To elucidate the formation mechanism, insights from thermogravimetric analysis were combined with results from electron paramagnetic resonance. The composite was electrochemically characterized by cyclic voltammetry, galvanostatic cycling and by the galvanostatic intermittent titration technique. The results showed that the synthesized material is a composite of sodium titanate and amorphous carbon, the former of which contains Ti3+ and Ti4+. Ti3+ is produced during the carbothermic reduction of Ti4+ when annealing the precursor. The particles were rod-shaped. Since this composite shows a high stability (89% capacity retention after 500 cycles at 1C) and capacity (135 mAh g-1 at 0.1C, 105 mAh g-1 at 1C and 61 mAh g-1 at 10C), and requires only abundant and inexpensive elements, we believe that this material presents a big step forward toward a commercially viable NIB.

Resume : To meet the trends in the electronics industry towards being miniature, portable, and highly integrated, new energy-storage units are in urgent demand. Supercapacitors are an emerging class of energy storage devices that holds great promise for future electronic systems due to their superior power density, stability and cycle life compared with batteries. In particular, micro-supercapacitors with in-plane structure are attracting a lot of attention. Inkjet printing is considered as a promising technique for micro-supercapacitors fabrication owing to its simple, versatile, environmental-friendly and low-cost features. Here we prepared an ink containing two-dimensional ?-MnO2 nanosheets with an average lateral size of 89 nm and a sheet thickness around 1 nm. By engineering the ink formulation of ?-MnO2 ink, we were able to inkjet print on arbitrary substrates to form ?-MnO2 patterns and without undesired ?coffee-ring? effect. All-solid-state symmetrical micro-supercapacitors based on PEDOT: PSS and ?-MnO2 nanosheets materials were fabricated by inkjet printing. The fabricated micro-supercapacitors showed excellent flexibility and good cycling stability with a capacitance retention of 88% after 3 600 charge-discharge cycles. The micro-supercapacitors attained the highest volumetric capacitance of 2.4 F cm-3, and an energy density of 1.8 ×10-4 Wh cm-3 at a power density of 0.018 W cm-3, which is comparable with other devices.

Resume : Molybdenum oxide nanosheets are interesting materials for energy storage, catalysis, and gas sensor applications.1 However, they are traditionally prepared via a variety of approaches which require the use of high temperature or organic solvents.2,3 Herein, we report the synthesis of MoO3-x nanosheets (where x denotes oxygen vacancy) via a one-step water based exfoliation strategy using bulk molybdenum oxides precursors.4 Scanning and transmission electron microscopy show that the MoO3-x has a typical nanosheet morphology with a few nanometer thickness. The MoO3-x nanosheets display localized surface plasmon resonance (LSPR), which can be enhanced by modifying the morphology and the amount of oxygen vacancies (x) using chemical and/or photochemical treatments. The aqueous suspension of the MoO3-x nanosheets was drop-cast onto carbon paper and this material was then used as binder free electrodes for supercapacitor applications. The electrodes showed promising performance regarding capacitance and rate capability in acidified sodium sulphate solutions. The facile green synthesis of MoO3-x nanosheets coupled with their significant photochemical and electrochemical properties pave the way for the use of the nanosheets in a variety of applications. References: (1) de Castro, I. A.; Datta, R. S.; Ou, J. Z.; Castellanos-Gomez, A.; Sriram, S.; Daeneke, T.; Kalantar-zadeh, K. Molybdenum Oxides - From Fundamentals to Functionality. Adv. Mater. 2017, 29 (40), 1701619. (2) Xiao, X.; Song, H.; Lin, S.; Zhou, Y.; Zhan, X.; Hu, Z.; Zhang, Q.; Sun, J.; Yang, B.; Li, T.; Jiao, L.; Zhou, J.; Tang, J.; Gogotsi, Y. Scalable Salt-Templated Synthesis of Two-Dimensional Transition Metal Oxides. Nat. Commun. 2016, 7, 11296. (3) Alsaif, M. M. Y. A.; Field, M. R.; Daeneke, T.; Chrimes, A. F.; Zhang, W.; Carey, B. J.; Berean, K. J.; Walia, S.; van Embden, J.; Zhang, B.; Latham, K.; Kalantar-zadeh, K.; Ou, J. Z. Exfoliation Solvent Dependent Plasmon Resonances in Two-Dimensional Sub-Stoichiometric Molybdenum Oxide Nanoflakes. ACS Appl. Mater. Interfaces 2016, 8 (5), 3482?3493. (4) Etman A. S.; Abdelhamid H. N.; Yuan Y.; Wang L.; Zou X.; Sun J. Facile Water Based Strategy for Synthesizing MoO3-x Nanosheets: Efficient Visible Light Photocatalyst for Dye Degradation. ACS Omega. in Press.

Resume : Hollow nanostructures of various metal oxides, with enhanced surface area and volume, are gaining attention in supercapacitors and batteries. We propose a novel, facile and cost-effective solution based synthesis route for obtaining hollow structures of Cu- based oxide. These oxides are known to have high theoretical specific capacitance, redox capability, stable phase and tunable morphologies, which makes them useful in electrochemical systems. The characteristics of these hollow structures is strongly controlled by the underlying particle growth principle/mechanism. The electrochemical activity for hollow nanostructures was found to be >70% higher than the solid counterparts. To further increase, the specific capacitance of the devices fabricated using such hollow nanostructures; we are proposing the addition of redox electrolyte additives. The usefulness of this strategy is proven by the results obtained using redox additives such as KI and K4(Fe(CN)6) in 2 M KOH. Additional increase of >50% could be observed in the overall specific capacitance. Symmetric supercapacitors fabricated after the addition of optimized quantity of redox electrolyte additives also lead colossal enhancement in energy and power densities, which makes these materials even more useful for industrial applications.

Resume : Lithium transition metal oxides are widely used cathode materials in commercial lithium-ion batteries. Recently, Li-rich nickel cobalt manganese oxide (Li-rich NCM) cathode materials became popular as specific discharge capacities of more than 280 mAh/g can be gained compared to 200 mAh/g for conventional NCM. However, Li-rich NCM shows stronger capacity and voltage fading during cycling. Inorganic coatings on cathode particles can improve the capacity retention of this material system, but their working mechanism is still not well understood. In this study, the impact of alumina particle coating on electrochemical degradation of Li-rich NCM that was coated by atomic layer deposition and chemical solution deposition was investigated. The pristine and modified powders were compared by electrochemical cycling to reveal differences in the electrochemistry. The various surface modifications affect the long-term stability, the surface resistances and the charge-/discharge profiles significantly. The degree of coverage and the morphology of the particles? coatings were investigated via Time-of-Flight Secondary Ion Mass Spectrometry, Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, elemental analysis and Transmission Electron Microscopy. Despite the strong observed differences of electrochemical performances, it turned out that none of the powder particles was coated with a thick and homogenous alumina film covering the surface completely.

Resume : Composites of transition metal oxides with graphene or graphene oxide (GO), are considered as potential anode materials for rechargeable Li-ion batteries with enhanced performance and capacity, due to the combination of the high load storage capacity of the oxide with the large conductivity value of the C compound [1,2]. In this work, composites of hexagonal molybdenum oxide (h-MoO3) microrods and graphene or GO, have been obtained by a scalable soft chemistry method based on the precipitation of ammonium heptamolybdate. The samples have been characterized by a wide range of complementary techniques including X-ray diffraction, scanning electron microscopy, X-ray microanalysis, micro-Raman and photoluminescence spectroscopies. h-MoO3 microrods were found to be covered by graphene and GO layers. This coating increases the specific capacity (compared to the reference h-MoO3 electrode) and the stability, exceeding a value of 600 mA h /g at a current density of 1 A/g after more than 130 cycles. These excellent storage properties are attributed to the effect of graphene and GO layers, which are interspersed between the h-MoO3 rods preventing both their aggregation and the electrode from being sprayed as a result of the large volume changes that occur during Li insertion-deinsertion cycles. [1] J Lu et al; Nat. Nanotechnol 11, 1031 (2016). [2] W. Sun et al; Nanoscale 6, 11528 (2014).

Resume : Metal oxide based lithium-ion battery anode materials are of increasing interest owing to their improved charge capacities over graphite, ease of synthesis and low cost. The lithium capacities and cycle life of anode materials are highly dependent on their morphology and composition. While the relevant literature is numerous, fundamental studies exploring the underlying factors that affect the cyclability of metal oxide materials are lacking. In this presentation, electrochemical testing results of various nanostructured metal oxide anode materials synthesized by wet-chemistry methods will be presented and compared. These oxide materials will differ from each other in terms of; i) the total number of different metals in the structure, ii) metal-to-oxygen ratio in generalized MxOy anode material, iii) hybrid metal-oxide nanocomposite structure and iv) composition.

Resume : Solar energy,as the cleanest and least limited energy source, becomes increasingly hot over recent years. Polyoxometalates (POMs) are a structurally diverse family of anionic metal oxide molecular compounds with extent applications in photocatalysis and photoelecrocatalysis. Unfortunately, POMs can be excited (POMs) mainly under UV irradiation. To address this problem, POMs can be linked to visible light sensitizer, such a porphyrins,which possess strong visible absorptions and ultrafast photoinduced charge separation [1]. We use different methods to discuss the absorption spectra, electronic transition properties, and photovoltaic performance of porphyrin-polyoxometalates complexes for p-type dye-sensitized solar cells (DSSCs). The absorption spectra of various dyes exhibit larger and broader absorptions compared to that of other dye by the introduction of POM. The photovoltaic performances of Polyoxometalate-Porphyrin hybrid complexes for high-efficiency DSSCs. This paper is expected to advance the design of porphyrin-POM hybrid dyes with excellent performance in DSSCs [2]. References [1] Costa-Coquelard, C.; Sorgues,S.; Ruhlmann, L. J. Phys. Chem.A, 2010,114 (22), 6394. [2] Ting Zhang, Wei Guan, Shizheng Wen, Tengying Ma, Likai Yan, and Zhongmin Su, J. Phys. Chem. C, 2014, 118 (51), 29623?29628.

Resume : This work uses the ultrasonic spray pyrolysis deposition (USPD) method to grow magnesium oxide (MgO) nanorod arrays (NRAs). The magnesium acetate (Mg(CH3COO)2) is dissolved in the methanol as a precursor solution to grow MgO NRAs. The precursor solution which was misted by the ultrasonic vibration generator is transported to the substrate by the air gas flow. The substrate temperature is set to be 550 degrees Celsius for 10 minutes to grow MgO NRAs. It is found that MgO NRAs have a height of 70 nm and are grown on a 60 nm MgO film. Therefore, the authors presume that the growth of MgO NRAs by the USPD can be divided into two steps. First, the 60 nm MgO film is deposited on the substrate as a seed layer. After that, the MgO NRAs with the height of 70 nm are grown on the seed layer. The structural, chemical, and optical characteristics of the MgO NRAs are investigated, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ellipsometer, and photoluminescence (PL). The SEM image suggests that the shape of the MgO NRAs is square and the length is approximately 40 nm to 50 nm. Also, the density of the MgO NRAs is 6×109 cm-2. The TEM image shows that the height of the MgO NRAs is 70 nm and a 60 nm MgO film which serves as a seed layer was found under the MgO NRAs. The (200) and (220) crystal orientations are shown in the XRD spectrum. Therefore, the MgO NRAs is cubic structure which is coherent with the observation from the SEM image. Oxygen deficiencies are found in the XPS analysis. The PL spectrum indicates that the neutral oxygen deficiencies and positively charged oxygen deficiencies are existing in the MgO NRAs. Further, the refractive index and extinction coefficient of the MgO NRAs are 1.62 and 0 at the wavelength of 380 nm. This result suggests that the MgO NRA do not absorb UV light. Three different GaN-based ultraviolet light-emitting diodes (UV LEDs) are prepared. The UV LED with the present MgO NRAs is denoted as LED-A, with the standard SiO2 passivation is denoted as LED-B, and without any passivation layer is denoted as LED-C. The values of the series resistance of LED-A, LED-B, and LED-C are 1.87 ?, 1.6 ?, and 1.6 ?, respectively. It is found that LED-A has higher series resistance compared to LED-B and LED-C. However, the values of the light output power at 350 mA current injection of LED-A, LED-B, and LED-C are 234 mW, 205 mW, and 194 mW, respectively. The significant improvement in the light output power is helpful to enhance the light extraction efficiency so that higher external quantum efficiency is obtained in LED-A. The values of the external quantum efficiency of LED-A, LED-B, and LED-C are 18.01%, 16.08%, and 14.86%. These results suggest that the present MgO NRAs enhanced the efficiency of the GaN-based UV LED.

Resume : The ferrimagnetic rare earth iron garnets, R3Fe5O12, present a unique group of materials, which have become interesting for their novel magnetic and magneto-optical properties. Mixed rare earth iron garnets Sm3-xYbxFe5O12 (x = 0.75, 1.5, 2.25), Dy1.5RE1.5Fe5O12 (RE = Ho, Er, Tm) and Lu3-xEuxFe5O12 (x = 0.75, 1.5, 2.25) were prepared by an aqueous sol-gel method. The obtained dried gels were ground in an agate mortar and preheated at 800 °C for 2 h. Final sintering was performed at 1000, 900 or 800 °C for 10 h to obtain Sm3-xYbxFe5O12 (x = 0.75, 1.5, 2.25), Dy1.5RE1.5Fe5O12 (RE = Ho, Er, Tm),and Lu3-xEuxFe5O12 (x = 0.75, 1.5, 2.25), respectively. Different final annealing temperatures were chosen according to previously obtained results. The measured XRD patterns revealed that single phase garnets were obtained in the case of Sm3 xYbxFe5O12 (x = 0.75, 1.5, 2.25) and Dy1.5RE1.5Fe5O12 (RE = Ho, Er, Tm). As expected, the changes in the peak position in the XRD patterns of Sm3-xYbxFe5O12 (x = 0.75, 1.5, 2.25) garnets were observed, as Yb3+ ion has smaller ionic radius compared to Sm3+ ion. The shift of diffraction peaks appeared in the XRD patterns of Dy1.5RE1.5Fe5O12 (RE = Ho, Er, Tm) compounds. This was due to the difference in the ionic radius of Ho3+, Er3+ and Tm3+ ions. Synthesis of Lu3-xEuxFe5O12 (x = 0.75, 1.5, 2.25) at 800 °C led to the perovskite structure compounds with some appearance of the garnet phase when x = 2.25.

Resume : In2O3 and ITO films on "cold" (20 °C) and "hot" (600 °C) Al2O3 (012) substrates deposited by magnetron sputtering in an argon-oxygen atmosphere were studied. The deposition time of ITO films on "cold" substrates was 2 hours; current - 80 mA (AC) + 5 mA (DC); voltage - 250 V. Other films were deposited for 1 hour; current - 100 mA (AC) + 50 mA (DC); voltage - 300 V. The films investigated by multiangle ellipsometry. The results was interpretated according to our method of complex investigation of thin-film coatings [1]. The films are well described by a model of a homogeneous material with a rough surface [2] modeled as linear decrease of the refractive indices in the direction to surface. The thickness and growth rates of the films on “cold” substrates (600-650 nm, 0.24 nm/(min*W)) is greater than on “hot” ones (~ 400 nm, 0.15 nm/(min*W)), independently of doping with tin and magnetron power. The refractive indexes are 1.9 and 2.1, accordingly. The films have two kinds of surface layer - thin (~ 20 nm) with a sharp decrease in the refractive index by 25-30% and thick (~ 70 nm) with a small (5-7%) decrease. The first was observed for undoped films on “hot” substrates and for doped films on “cold” substrates. In other cases, the second kind of layer was observed. [1] Tikhii A.A., Gritskikh V.A., Kara-Murza S.V., Nikolaenko Yu.M., Zhikharev I.V., Opt. and Spect., 112, 2, 300–304 (2012). [2] Szczyrbowski J., Dietrich A., Hoffman H., Phys. Stat. Sol. (a) 69, 217-226 (1982).

Resume : Despite the considerable demand for bio-inspired superhydrophobic surfaces with highly transparent, self-cleaning, and self-healable properties, a facile and scalable fabrication method for multifunctional superhydrophobic films with strong chemical networks has rarely been established. Here, we present a rationally designed facile one-step construction of covalently networked, transparent, self-cleaning, and self-healable superhydrophobic films via a one-step preparation and single-reaction process of multi-components. As coating materials for achieving the one-step fabrication of multifunctional superhydrophobic films, we included two different sizes of Al2O3 nanoparticles for hierarchical micro/nano dual-scale structures and transparent films, fluoroalkylsilane for both low surface energy and covalent binding functions, and aluminum nitrate for aluminum oxide networked films. Based on stability tests for the robust film compositions, the optimized, covalently linked superhydrophobic composite films with a high water contact angle (>160°) and low sliding angle (< 1°) showed excellent chemical and thermal stability (up to 400 °C), transparency (≈ 80%), self-healing, self-cleaning, and waterproof abilities. Therefore, the rationally designed, covalently networked superhydrophobic composite films fabricated via a one-step solution-based process can be further utilized for various optical and optoelectronic applications.

Resume : We have investigated the effects of sulfur passivation using aqueous ((NH4)2S:DI) and alcoholic ((NH4)2S:IPA) ammonium sulfide solutions on Ni ohmic contacts to InAs epilayer grown on In0.56Ga0.47As. Among aqueous and alcoholic ammonium sulfide treatments, alcoholic ammonium sulfide treatment on InAs surface prior to metal deposition proved to more effective in improving the ohmic contact as compared to the untreated and aqueous ammonium sulfide treated samples. A low specific contact resistivity of 4.09 x10e-9 ohm∙cm2 was obtained for the Ni/InAs contact with alcoholic ammonium sulfide treatment against the values of 2.15x10e-6 and 1.06x10e-7 ohm∙cm2 obtained for the untreated and aqueous ammonium sulfide treated samples. X-ray photoelectron-spectroscopy analysis showed that aqueous and alcoholic ammonium sulfide treatments are effective in the removal of As2O3 native oxide. Alcoholic ammonium sulfide treatment of the InAs surface indicated a better sulfur passivation with the As-S/As-In bonding ratio being 3.1 as against the ratio of 0.8 in the case of aqueous ammonium sulfide treatment. The ultraviolet photoelectron spectroscopy measurements indicated a low barrier height between Ni and alcoholic ammonium sulfide treated InAs surface owed to its high work function of 4.35 eV as against the 3.78 and 4.16 eV for the untreated and aqueous ammonium sulfide treated InAs surfaces. An energy-level alignment diagram of the untreated, aqueous and alcoholic ammonium sulfide treated surfaces with respect to Ni is also presented and discussed. The improved specific contact resistivity of the Ni contact to alcoholic ammonium sulfide treated InAs surface is associated with the better sulfur passivation of the surface indicated by the high bonding ratio of sulfur to As.

Resume : ZnO nanowires (NWs) are promising building blocks for a wide variety of sensing, optoelectronic, and electronic devices. For those applications, extrinsic doping should be controlled thoroughly. ZnO can intentionally be n-doped, for example by incorporating metal dopants. The doping of ZnO NWs has however been mainly performed by vapour phase deposition techniques and is still a major issue by solution deposition techniques. In the present work, ZnO NWs are doped with different metal dopants by using the low-cost, low-temperature, and easily implemented chemical bath deposition technique. Metal nitrate is basically added in various concentrations to the standard precursors [1] in deionized water. This addition completely modifies the structural morphology of ZnO NWs, as shown by electron microscopy [2]. The formation mechanisms are investigated and supported by thermodynamic simulations yielding theoretical solubility plots and speciation diagrams. Their dependence on the pH of the solution through the addition of ammonia is further studied [3]. The incorporation of metal dopants is eventually investigated by energy dispersive x-ray spectroscopy using scanning transmission electron microscopy and by temperature-dependent Raman spectroscopy, showing the occurrence of characteristic additional modes. [1] R. Parize et al., J. Phys. Chem. C 120, 5242 (2016) [2] C. Verrier et al., J. Phys. Chem. C 121, 3573 (2017) [3] C. Verrier et al., Inorganic Chemistry 56, 3573 (2017)

Resume : The functional characteristics of thin films planar solar cells are very sensitive to the presence of pores, voids or holes. Thus deposition of compact, dense and uniform layers is essential in that technology. In nano – sized structures the shorts are a common problem and reason for failures. These issues are especially important in organometalic perovskite solar cells where the active layers are in the nano metric scale. In this emerging technology reduction of cost to efficiency ratio is a serious barrier for commercialization therefore application of cheap and abundant materials as electron selective layer will be advantage. In this work we have investigated different parameters of the process of deposition of SnO2 thin films by spin coatings which influence its compactness and impenetrability. The thermal behavior of the precursor substances was investigated by Differential Scanning Calorimetry in order to estimate the points of the important chemical and phase transformations and in consequence to define an appropriate annealing regime. Influences of the thermal treatments on the properties of the films were investigated by UV – Vis measurements, Raman spectroscopy, X-ray diffractometry, Scanning Electron Microscopy and Photoluminescence. The final assessments of the coverage ability of the SnO2 films were performed by cyclic voltammetry in aqueous redox solution. Between the used solvents ethanol, methanol and isopropanol for precursor (Sn4 ) solutions the last ones give uniform layers without pinholes at low temperatures. After annealing in the temperature interval 100 – 180 oC the layers crystallized in typical tetragonal Rutile configuration. The electrical leakage of the films depends on the concentration of the precursor solution, but at higher concentrations, over 0.5 M SnCl4.5H2O, the formed films are rugged and the root mean square (RMS) roughness increase sharply.

Resume : New features of light interaction with the nanostructured oxide surface of some heterostructures (ZnCdO-GaSe, ZnCdO-InSe, In2O3-InSe), fabricated by different methods (magnetron sputtering, crystal surface oxidation) are established. Oxide films as a frontal layer are also an active part of heterostructures, the substrates of which are semiconductors with a van der Waals surface and hole conductivity. In the photoresponse spectra of these structures, an additional band of photosensitivity is detected, the intensity of which is the higher the more ordered is the aggregate of surface nanoobjects of the oxide. AFM-images of oxide surfaces are presented, from which it can be seen that the technology of oxide formation, the type of substrate strongly influence the shape and size of nanoobjects, their self-organization on the surface. The obtained results can be used in optimizing the parameters of photodetectors on the basis of the investigated heterostructures.

Resume : Nickel oxide (NiOx) is an attractive hole-transporting material for perovskite solar cells (PSCs) due to its high hole mobility, larger bandgap, deep valence band, good stability, and easy processability. However, despite of promising characteristics, detailed studies of NiOx under various process conditions on the performance of PSCs have not been thoroughly investigated and compared so far. Therefore, we systemically studied the effect of the NiOx produced by various process conditions in terms of concentration, thickness, and temperature. Moreover, the optimal device fabrication conditions were further achieved and analyzed the morphology, charge transport, PSC-efficiency, and stability. As a result, the best power conversion efficiency of 17.82% was obtained with a Jsc of 20.16 mA/cm2, a Voc of 1.12 V, and a FF of 78.86% with no distinct hysteresis. Based on these observations, we provide recommendations for effect of NiOx hole-transporting layer for perovskite solar cell devices.

Resume : Zinc oxide (ZnO) has been attracting electron transport layer (ETL) for perovskite solar cell (PSCs) due to its high electron mobility, good optical transparency and environment stability, and its bi-layer structure with the small molecule [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has been studied to improve the performance of PSCs. However, detailed studies on the effect of PCBM / ZnO bi-layers on PSC performance under various process conditions have not been thoroughly investigated and have not been compared so far. Therefore, we systematically studied the effect of thickness and morphology of PCBM and ZnO on PSCs efficiency and stability. Furthermore, we also optimized PCBM / ZnO bi-layer, as a result, obtained the best power conversion efficiency of 16.39% with JSC of 19.72 mA/cm2, VOC of 1.10 V, and a FF of 75.77% without hysteresis.

Resume : Titanium dioxide (TiO2) has recently attracted considerable attention for its outstanding physical and opto-electronic properties. Due to its wide band gap (anatase 3.2 eV and rutile 3.0 eV [1]), high chemical stability and low cost, TiO2 is regarded a promising material for a wide range of applications including photocatalysis, gas sensors, dye-sensitized solar cells, biomedical fields, self-cleaning and optical filters. Among the aforamentioned applications, TiO2 based solar cells, constructed in many device architectures (planer and core-shell types), have attracted particular attention. So far, a number of routes have been reported for the deposition of TiO2 thin films such as atomic layer deposition, sputtering, sol-gel and pulsed laser deposition. Among these, the sol-gel technique offers several advantages over them such as the well control over the structure/homogeneity of the deposited film, the low energy consumption, the simplicity of the approach (no need for special /expensive equipment) and the production of the films at large scales. In addition to these, the sol-gel route provides a well control over the modification optical and structural characteristics of the deposited TiO2 thin film by tuning growth parameters such as solution concentration, deposition time and temparature. The main objective of this study was to investigate the effect of growth parameters on optical, structural and electrical properties of the deposited TiO2 thin film on both glass and FTO-precoated glass substartes, which was employed not only as a seed layer for the synthesis of TiO2 nanorods (NRs) by hydrothermal technique but also a buffer layer for the construction of n-TiO2 film/nanowire/p-CZTS structured solar cells. For the construction of the TiO2 based solar cells (planer and core-shell) , the absorber layer was chosen to be thermally evaporated Cu2ZnSnS4 (CZTS) thin films. The photovoltaic performance of the fabricated planer and core-shell like devices was tested under standard test conditions (AM 1.5G) and their solar parameters were determined.

Resume : Four MFe2O4 spinel ferrites (M=Co, Mn, Ni, Zn) were synthesized with a low-temperature green hydrothermal route [1]. Given the influence that synthetic parameters hold over the final product [1], understanding the effects of these parameters can help in the development and optimization of simple, mild and green synthetic protocols for inorganic oxides [2]. In this framework, several samples were prepared within different time frames to investigate the evolution of the product MFe2O4 compound during the synthetic procedure. The resulting solids were characterised with a wide array of analytical techniques both in the atomic (XAS) and long range (XRD, SAXS) order. The morphological evolution of ZnFe2O4 during heating was further investigated through TEM micrographs collected from samples sporting different synthesis times. ____ [1] Diodati Stefano, Pandolfo Luciano, Caneschi Andrea, Gialanella Stefano.and Gross Silvia Nano Res., 2014 7 1027-1042 [2] Diodati Stefano, Dolcet Paolo, Casarin Maurizio and Gross Silvia Chem. Rev. 2015, 115, 11449−11502

Resume : Zinc sulfide is a promising material that is capable to combine luminescence properties with good thermal stability and low toxicity. These characteristics makes zinc sulfide one of the most promising material for, inter alia, the development of new quantum dots for bioimaging applications [1]. In this framework, we exploited the unique features of a microfluidic reaction setup in order to move from traditional batch synthetic approaches to a more convenient flow reaction setup. This novel and simple microfluidic approach was used to produce vary small (3 nm) ZnS nanoparticles. The particles where obtained almost instantaneously by simply micro-mixing two precursors solutions at room temperature and using only water as solvent. XRD and XPS analysis were performed to assess the obtained crystal structure and surface composition, while the particles size and morphology were studied by TEM micrographs. The specific surface area of the nanostructured material was then determined by BET. ____ [1] Fang, X. Prog. Mater. Sci. 2011, 56, 175-287.

Resume : Miniemulsion is an innovative method to obtain, already at room temperature, crystalline inorganic materials by exploiting a reaction occurring inside the confined space of independent nanometric-sized droplets. Despite being a promising technique, to the best of our knowledge no systematic study on the crystallization phenomena under miniemulsion conditions has been carried out yet. In this regard, we performed by Small-Angle X-ray Scattering (SAXS) an in-situ and time-resolved investigation of the crystallization process of ZnS synthetized by inverse miniemulsion [1]. The experimental setup for this experiment was composed of a reactor equipped with a probe-type sonicator, connected with a continuous flow equipment. While the reaction was carried out, the reaction mixture was continuously flowed thought a homemade measurement cell mounted in the SAXS beamline of the synchrotron facility Elettra (Trieste), to follow the structural and morphological evolution of the system in real-time. The obtained SAXS profiles were then fitted in order to get an insight of the dimension and the number of the formed particles with time. Moreover, the same setup was employed to investigate the miniemulsion without the presence of the ZnS precursors, and the effect of the surfactant concentration on the synthesis. ____ [1] P. Dolcet, S. Gross et al., Eur. J. Inorg. Chem., 2015 (4) 706

Resume : GaSe from a class of 2D layered semiconductors is a promising material for usage in THz electronics; as the basis of various optoelectronic devices; a matrix for H2 storage; and substrates in planar nanotechnologies, etc. It is generally accepted that van der Waals (0001) surface (vdWS) of GaSe, formed by close-packed and chemically saturated Se atoms, is inertial to sorption of foreign atoms (molecules) from the atmosphere. Previously we have shown that a long term keeping of GaSe under ambient conditions on air leads to formation of native oxide (Ox) films of Ga2O3 nanoparticles embedded in a composite dielectric matrix (selenium oxides and gallium salts of selenic asids) on vdWS of GaSe. As appears from experimental investigations such Ox films can be used as active elements of humidity CO, H2, and other gas sensors. In this report we demonstrate that ageing of GaSe wafers in water (regardless of the O2 presence) under daylight illumination leads to interaction between vdWS of GaSe and H2O. The formation of the Ox films (with the same structure and chemical composition) occurs due to the re-crystallization of the reaction products from solution on vdWS of GaSe. Also, we discuss the reasons for interaction of H2O with atomically smooth vdWS but not with the lateral surfaces of GaSe wafers obtained by mechanical destruction of each layer; analyze the kinetics of chemical and photochemical reactions; demonstrate the possibility to use such Ox films as humidity sensors.

Resume : NiTiO3/NiTiS3 heterostructures comprised of NiTiO3 nanorods and NiTiS3 nanoparticles were synthesized via a solution based method at RT followed by an in situ anion exchange reaction. NiTiO3 was successfully synthesized by a solution based synthesis by ethylene – glycol route at room temperature followed by calcination at 600oC in air, obtaining nanorods with lengths ranging from 2.5 to 3.0 μm. In order to modify the obtained NiTiO3 nanorods with NiTiS3 nanoparticles, a solutions of distilled water, NiTiO3 powder and sulfur precursor was used and transfered into a Teflon-lined stainless steel autoclave. The final heterostructured system was characterized by X-Ray powder diffraction, Field-Emission Scanning Electron Microscope, Energy Dispersive X-Ray Spectroscope, Transmittance Electron Microscope and UV-Visible Spectroscope and the results showed that the bulk of the nanorod is pure ilmenite NiTiO3 while its surface consists of NiTiS3 nanoparticles which are ~ 50 nm in diameter. The O ions on the lattice of NiTiO3 successfully replaced by the S ions that the source of thioacetamide provide to the system and helped by the high pressure via the in situ anion exchange reaction, leading to the formation of more NiTiS3. EDX proves that the composite NiTiO3/NiTiS3 consists of Ni, Ti, O and S elements.

Resume : The surprising and exotic properties of oxidize form of graphene has one of the application in fuel cell. In PEMFCs, it is based on the polymer electrolyte membrane typically NafionTM which is a perflurosulfonic acid (PFSA) membrane that many deficit subsistence such as expensive, fuel crossover, dehydration, gas permeation and catalytic incorporation etc. Pure grapheme oxide (GO) shows good electronic insulation when enough oxygen bonded to its surface (O/C is over 6), and also shows relatively high proton conductivity in humidified condition without any acidic functional group. However, using the GO as a pure electrolyte in fuel cell resulting severe membrane degradation and losses of surface functional groups creates an electronic conduction through the membrane. Therefore, we proposed a new membrane that, a double-layer composite electrolyte membrane consisting of GO layer and metal hydrogen permeable thin film. The hydrogen permeable metal thin film was deposited using Pd or Ni64 Zr36 target by dc magnetron sputtering with appropriate pressure and deposition time to reach about 40nm of the thickness. This properties of the fabricated composite membrane was investigated on it’s surface morphology and fuel crossover as well as its structure, physical and chemical stabilities, proton conductivity, water uptake by using SEM, GC, XRD, FTIR, Raman Spectroscopy, TG/DTA and Impedance Analyzer. The performance of the graphene oxide hydrogen membrane fuel cell (GOHMFC) using the composite electrolyte membrane was also evaluated

Resume : Phase-pure, well-crystallized, and luminescent Eu:ZnGa2O4 nanoparticles were obtained in high yields (>93%) at 200 °C, within 10 min, through microwave-assisted solution-phase synthesis. The structural and optical properties were studied by XRD, HR-TEM and photoluminescence (PL) spectroscopy. Nanocrystalline, phase pure material was formed with crystallite size ~7 nm. PL studies reveal an intense red band at 615 nm pertaining to 5D0 → 7F2 transitions when excited at 395 nm. Further, as synthesized nanoparticles were processed by a novel, radiation based rapid annealing technique. The processing temperature ranging from 400-900 °C achieved at a heating rate of 200 °C/minute. Significant improvement in the emission intensity was observed while the XRD patterns were similar at different processing temperatures. Our report demonstrates the efficacy of swift microwave-assisted synthesis, combined with 10 min rapid annealing, in providing a doped red phosphor of high colour purity suitable for LEDs and display applications.

Resume : The versatility of wet chemical methods allows the exploration of novel crystallization pathways for metal oxides thin films and makes them fundamental in the search of low-temperature methods. The benefits obtained from decreasing the processing temperature span from minimizing the environmental impact to reducing the production costs. More challenging is the preparation of complex oxide layers at temperatures compatible with their direct integration in flexible substrates (≤350 ºC). However, their high crystallization temperatures (>600 ºC) impede the development of such multifunctional devices. Significant efforts have been devoted in our group to address this challenge.1 The result is an efficient series of strategies for the low-temperature processing of oxide layers using light as an alternative energy source to induce crystallization by photochemistry. Here, it will be shown how the crystallization of photoferroic BiFeO3, ferroelectric Pb(Zr,Ti)O3 or photocatalytic β-Bi2O3 can be achieved at temperatures between 250-350 ºC. This requires the synthesis of novel photosensitive solutions (modified metal alkoxides, charge-transfer metal complexes, structurally designed molecular compounds) and precise control over the reactions promoted by UV light (photochemical cleavage, ozonolysis, condensation, photocatalysis). [1] Bretos et al., Chem. Soc. Rev., 2018, DOI: 10.1039/c6cs00917d. Supported by Spanish Project MAT2016-76851-R and Fundación General CSIC (ComFuturo Programme).

Resume : Olivine LiMn1-2xVxPO4 has been synthesized through a diamine-assisted reflux method. As using the doping source of VOC2O4, V4 can easily substitute Mn2 in a wide range of concentration (0 ≤ x ≤ 0.30). The significance of the re-fluxing under inert atmosphere provides a homogeneous synthesized environment and prevents the phosphate and vanadium ion further oxidation/ reduction. The particle sizes would be reduced and surface area would be increased in high vanadium concentration. The enhancement of V4 made LiMn1-2xVxPO4 particle grow through [101] direction, resulting in a thin thickness of (020) facets. X-ray diffraction also revealed lattice shrinkage in LiMn1-2xVxPO4. In the electrochemical test, substitution of V4 prolongs the discharge plateau around 4.0 V, making the total capacity increase to 155 mAh/g, higher than the pristine LiMnPO4/C (125 mAh/g). As studying through in-situ XAS, it revealed a V4 /V5 oxidation occurring below 4.3 V. In discharge process, a muti-charge transfer of V5 /V4 /V3 occurred as discharging to 2.0 V. The substitution of V4 improves the Li-ion transportation by lowering the charge-transfer resistance and enhancing the Li-diffusivity to an order of magnitude. In summary, the LiMn1-2xVxPO4 is a potential cathode material that V4 can improve the Li-ion diffusion kinetic and provide additional capacity during cycling.

Resume : ZnO, a high mobility n-type semiconductor, is a highly attractive transparent material for applications in optoelectronic devices. However, the manufacture of high quality ZnO thin films requires high temperatures and/or pressure, making the processes expensive. In this work we will demonstrate a biomimetic approach for the synthesis and deposition of ZnO films on Si substrates under mild ambient conditions. Simultaneous synthesis and deposition of ZnO nanoparticles (NPs) is achieved in this work by the use of dual affinity peptides (DAPs) as linkers. One segment of the DAP has a strong affinity to the substrate and the other promotes the synthesis of the NPs. The formation of 10-20 nm crystalline NPs in solution is confirmed by diffraction analysis and further characterization reveal 1[Zn]:1[O] stoichiometry. Initial results demonstrating the in-situ deposition of ZnO NPs on Si using the DAP linkers will also be presented. We will further show that the DAP monolayers reduce the work function of ZnO by ~260 meV. This work demonstrates the great potential of using low-cost and green biomimetic approaches for the fabrication of thin nanocrystalline inorganic films towards implementation in optoelectronic devices.

Resume : This study developed an ultra-efficient process for ion-selective electrosorption for phosphate in water based on graphene oxide (GO)/MgMn-type layered double hydroxide composite calcined at 300? (G/MgMn-LDHs-300). The high selective adsorptive electrodes by introducing high specific surface area and wettability of GO to the electrodes, as a result, enhancing ion electrosorption efficiency for phosphate-selective electrodes. Calcination process of G/MgMn-LDHs contributed to an amorphous phase with more active site for adsorption of phosphate. Moreover, GO can attract electrons from LDHs which help the oxidation process of Mn3+ to Mn4+ state during calcination. The maximum phosphate adsorption rate and phosphate selectivity coefficient to sulfate of G/MgMn-LDHs-300 electrode can reach 0.78 mg-P/g/min and 58.3 times, respectively. This study shows that ulta-efficient adsorption of phosphate could be achieved by G/MgMn-LDHs-300 composite electrodes. Moreover, this method can effectively reduce the process time and cost, which could be potentially applicable as a promising technology for phosphate removal.

Resume : ZnO is a well-known wide band-gap semiconductor material for optoelectronics, photovoltaics and sensors. ZnO nanocrystals doped with transitional metal are considered as a candidate for fabrication of diluted magnetic semiconductors which are promising for spintronic applications. Compared with other similar materials ZnO can be fabricated by several simple solution growth techniques. In this work we have investigated the influence of deposition parameters on the properties of ZnO nanocrystals doped with Ni and Co fabricated by chemical hydrothermal method. The concentration of the precursors, seed layer morphology and temperature were changed during the experiments. Concentration of transitional metals varied from 1/1 to 1/500 of the zinc nitrate concentration. Temperature varied in the range of 75 – 95 °C. The concentration of transitional metals in the obtained ZnO nanocrystals is up to 2.2 at.% as was shown by the XPS analysis. Introduction of Ni and Co drastically reduced the efficiency of photoluminescence. However the formation of magnetic metal clusters in the ZnO crystalline lattice led to the ferromagnetic behavior of the fabricated samples during ponderomotoric measurements in the temperature range of 77 – 1500 K. Obtained magnetic ZnO nanocrystals are useful for spin transistors, spin-polarized LED and magnetic sensor fabrication. The work has been supported by the Belarus Government Research Program grants 2.1.02 and 1.15.

Resume : New renewable energy has been drawing attention as fossil fuels are being depleted. The photovoltaic(PV) modules that make solar energy, a type of new renewable energy, can produce energy only during the daytime. Contamination of the surface of the PV module due to yellow sand, bird dropping and etc reduce the efficiency of power generation. Therefore, the anti-pollution treated PV module is an important technology for improving efficiency of PV power generation. In this study, the silica was reacted with a silane coupling agent to prepare a self-cleaning solution, which was used as a anti-pollution coating for the surface of PV module. The anti-pollution coating solution was spray coated on a glass substrate for a PV module, and then annealed at 400°C with a furnace. In this process, different content of silica were used to make different specimens. Contact angle, anti-pollution properties, hardness and adhesion were measured and analyzed. The optical properties of the specimens were also confirmed by using an integrating sphere in the UV-visible. As a result, it was confirmed that contact angle decreased with increasing silica content and self-cleaning property was improved. The process conditions of the functional film exhibiting improved properties were optimized. This functional film coating will help to maintain the cleanness of PV modules and high generating efficiency. In addition, this study will be useful to the application of requiring anti-pollution properties.

Resume : In this work, an attempt is made to obtain three-component compounds in the surface layers of CoSi2 by implanting O2+ ions in the surface layers of CoSi2 and to study morphology, composition and electronic properties. Analysis of the spectra of the AES showed that after the implantation of O2+ ions in CoSi2 in the near-surface region, there are Co-Si, Co-O, Si-O, Co-Si-O type compounds, and also unbound Co, Si and O atoms. T ≈ 900 K a three-component polycrystalline film of the CoSiO type is formed, consisting of separate blocks with dimensions of 20-50 nm. Between the blocks there are nanopores with dimensions of 10-20 nm and a depth of 40-50 Å. At a depth of d = 80 Å the atom concentrations of Si, Co, and O are 64-66 at%, 30-35 at.%, 1-2 at.%, respectively. Therefore, it can be assumed that for d ≥ 75 - 80 Å the stoichiometric composition of the CoSi2 film remains practically unchanged. The initial part of the dependence R(Ep) and δ(Ep) for the CoSiO/CoSi2(111) film is given. R is the coefficient of elastically reflected electrons; δ - coefficient of true-secondary electrons; Ep is the energy of the primary electrons. It is seen that in these dependences a number of characteristically distinct features are revealed which arise as a result of the excitation of interband electron transitions and plasma oscillations of valence electrons. There is a relationship between the structure, the course of the R(Ep) and δ(Ep) dependences with the band structure of semiconductors and dielectrics. The initial sharp decrease in the rate of growth of R is due to the transition of electrons from the ceiling of the valence band EV to the bottom of the conduction band EC. At the same time, a sharp initial growth δ is observed.

Resume : One of the core constituents of a thermal solar collector is a selective absorber which captures the solar energy and transfers it to a heat-transport fluid (glycerol/water mixture) circulating in tubes. When the solar panel is exposed to a strong solar radiation while the system is off, the temperature inside it may reach 200°C leading to glycerol vaporization and eventual heat-transport fluid degradation (stagnation temperature). In this work, we demonstrate that LaCoO3 is a promising material for thermal regulation due to its aptitude to reversibly change electrical and optical properties versus temperature. Such change occurs at a specific temperature called metal-insulator transition temperature (T??) and this thermochromic material deposited on an IR reflective substrate shows low IR emissivity below the T?? and high IR emissivity above. We show that emissivity variation (??) reaches 50% which allows to strongly reduce the stagnation temperature in a solar collector. Using a semi-industrial magnetron sputtering process, thin LaCoO3 films were deposited on A4-size aluminum substrates in metallic (RPC) and in-situ oxidative (RPE) regimes. The as-deposited amorphous films were annealed and synthesis conditions were adjusted to obtain the best ??. The characterization of the films with different thicknesses including SEM topographical analysis of surfaces, structural XRD analysis as well as infrared camera evaluation is presented and discussed.

Resume : Hydrogen plasma treatment increases the electrical conductivity of the nominally undoped (intrinsic) nanocrystalline ZnO thin films deposited by DC reactive magnetron sputtering of Zn target in the gas mixture of argon and oxygen plasma. However, changes (degradation) of electrical conductivity, free carrier concentration and localized defect density have been observed in hydrogenated ZnO thin films under high density DC electrical current. To clarify these changes, the mobility and carrier concentration were measured by the temperature dependent electrical resistivity and Hall effect using the van der Pauw method. We show how the ZnO degradation is related to crystallographic quality and defects by scanning electron microscopy (SEM), X-ray diffraction (XRD) and the optical spectroscopy in a broad spectral range from near UV to mid IR. This work was supported by the CSF project 16-10429J.

Resume : In this work we report the synthesis by solgel of zinc oxide doped with 〖Cu〗^(2+) ions, which was deposited on corning glass substrate. ZnO and ZnO:Cu thin films, are visible-transparent with a wurzite structure, and both have green photoluminescence emission properties. The structural, morphological and optical properties of the ZnO and ZnO:Cu films obtained were evaluated and compared to study the effect of the solgel process synthesis conditions and temperatures of thermal annealed process. The results obtained indicate that due to the addition of 〖Cu〗^(2+) ions, the ZnO network generates structural defects and these increase the properties of photoluminescence of ZnO:Cu thin films.

Resume : The electron transport layer, a vital component of photovoltaic device, contributes a lot to the performance of devices. The optimisation of electron transport layer has become one of the important issues in fabrication of photovoltaic devices. The n-type semiconductors, which have high electron affinity, are normally used as electron transport materials (ETMs). At present, TiO2 is the most widely used inorganic ETM in solar cells and has led to high power conversion efficiencies when used in perovskite solar cells. Nevertheless, TiO2 has some inherent limitations, such as the relatively low electron mobility. Besides, the high thermal annealing temperature of TiO2 (over 450°C) limits its application on the surface of flexible plastic substrate and leads the manufacture process to become costly. SnO2 is regarded as a superior alternative ETM to TiO2, with wider band gap of above 3.6eV and deeper conduction band. In addition, the electron mobility of SnO2 is approximately one hundred times higher than that of TiO2, so that the electron transport and extraction in SnO2 are more efficient. Whereas, the research of mesoporous SnO2 employed as ETL in solar cells remains limited. In this work, we report our recent work focussing on the use of planar and mesoporous SnO2 layers in perovskite and hybrid solar cells. A range of techniques such as microscopy, steady-state and time-resolved optical spectroscopy and device optoelectronic studies will be employed to determine the suitability of SnO2 layers in hybrid solar cells.

Resume : In this work, the performance of gold nanoparticles were investigated for stimulation of photosensitive materials for photonic applications. it was widely used for surface plasmon resonance experiments, not in the last place because of the manifestation of optical resonances in the visible spectral region. The localized surface plasmon resonance is rather easily observed in nanometer-sized metallic structures and widely used for measurements, sensing, in semiconductor devices and even in optical data storage. Firstly, gold nanoparticles on silica glass substrate satisfy the conditions for surface plasmon resonance in the green-red spectral range, where the chalcogenide glasses have the highest sensitivity. The gold nanostructures influence and enhance the optical, structural and volume changes and promote the exciton generation in gold nanoparticles/chalcogenide layer structure. The experimental results support the importance of localized electric fields in the photo-induced transformation of chalcogenide glasses as well as suggest new approaches to improve the performance of these optical recording media. Results may be utilized for direct, micrometer- or submicron size geometrical and optical pattern formation and used also for further development of the explanations of these effects in chalcogenide glasses. Besides of that, gold nanoparticles could be added to the organic light-sensitive material. The acrylate-based materials are frequently used for optical, holographic recording of optoelectronic elements due to photo-stimulated structural transformations. The holographic recording process and photo-polymerization effect could be enhanced by the localized plasmon field of the created gold nanostructures. Finally, gold nanoparticles widely used for electrochemical and optical sensor applications. Although these NPs can be synthesized in several ways, perhaps one of the simplest methods is the thermal annealing of pre-deposited thin films on glass or silicon surfaces. With this method, the parameters of the annealing process (time, temperature) and the pre-deposited thin film thickness influence and define the resulting size and distribution of the NPs on the surface. Localized surface plasmon resonance (LSPR) is a very sensitive optical phenomenon and can be utilized for a large variety of sensing purposes (chemical sensors, gas sensors, biosensors, etc.). Surface-enhanced Raman spectroscopy (SERS) is an analytical method which can significantly increase the yield of Raman scattering of target molecules adsorbed on the surface of metallic nanoparticles. The sensitivity of LSPR and SERS based devices is strongly depending on the used material and also on the size and geometry of the metallic nanoparticles. By controlling these parameters the plasmon absorption band can be tuned and the sensitivity can be optimized. The technological parameters of the generated gold nanoparticles were investigated and influence on the SERS and on the LSPR sensitivity was established. The LSPR sensitivity were simulated for gold nanocubes and nanospheres with MNPBEM Matlab toolbox. It was found that the enhancement factor (which characterize the increase in the peak shift for multi-particle arrangements compared to single-particle models) depends on the size of the nanoparticles and on the distance between the particles. This work was supported by GINOP- 2.3.2-15-2016-00041 project, which is co-financed by the European Union and European Social Fund. Istvan Csarnovics is grateful for the support through the New National Excellence Program of the Ministry of Human Capacities, supported by the ÚNKP-17-4 Attila Bonyár and Miklós Veres are grateful for the support of the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.

Resume : Possible improvement of solar cell efficiency through ZnO nanostructured thin films is studied through analysis of defect state distributions obtained via non-linear I-V characteristics, impedance spectroscopy, and transient photocurrents. An increased interface between electron and hole transporting layers will allow for a fast separation of the electron-hole pairs preventing their recombination. ZnO hierarchical nanorod thin films can provide the desired increase in interface area. The ZnO nanorod films were synthesized hydrothermally by placing the quartz/ITO substrates in a solution of zinc nitrate hexahydrate and sodium hydroxide at 90ºC. Hierarchical structures were obtained through a second deposition step. SEM was used to characterize the size and shape of the nanorods. Their diameter was about 125 nm in simple ZnO nanorods while hierarchical films showed additional 30 nm diameter nanowires growing on the side surfaces of the primary nanorods. Current-voltage measurements in the high field regime of 10 kV/cm were used to determine the density of trap states through analysis of space charge limited current theory (SCLC). The energetic distribution of such defect states could be determined through inverse Laplace transform of photocurrent decays, and the analysis of frequency dependent impedance spectra.

Resume : Oxide thin films of transition metals attract great attention due to their high pseudocapacitance and greater stability in the electrochemical system. By using photonic curing system for the pulsed light irradiation of the spray-coated Co-acetylacetonate solid precursor films in ambient condition, we can instantaneously photosynthesize nanocrystalline Co-oxide nanocomposite thin films, on commercial Pt-coated Si substrates, with a 3D nanostructure for their potential use as electrode materials in thin film based micro-supercapacitors. The first two pulses of irradiation of Co-acetylacetonate molecules result in self-assembly and crystallization of nanocomposite thin films while subsequent pulses improve the crystallinity of CoO nanograins, evaporate the carbon component via pulsed photothermal effect due to very high attenuation of light of Co-oxides, and lead to the phase transition from CoO to Co3O4 on the surface of thin films. The as-prepared thin films contain a higher content of rGO (reduced Graphitic Oxide) which results in higher faradaic capacitance and longer life cycle in 1 M KOH electrolyte in three-electrode cell configuration. The as-synthesized CoO-rGO nanocomposite thin films irradiated with 2 pulses showed specific areal capacitance as high as 5 mF/cm2 at 0.25 mA/cm2 after 20000 times of charge-discharge measurements. Future work will be focused on varying the number of pulses, pulse fluence values and other transition metals oxide films.

Resume : Cu2O films were deposited onto ITO substrate using successive ionic layer adsorption and reaction (SILAR) technique with different repetition cycles (40, 50, 60). The structural, optical, and surface morphological studies were carried out and reported. The structural study revealed that the crystalline quality is gradually enhanced with increase in number of cycles SILAR cycles with preferential orientation of (111). Optical study shows that the transmittance and optical band gap also changes with increase in SILAR cycles for Cu2O. SEM images revealed the morphology for ITO films were of nanowire like structures.

Resume : This work presents a new approach for room temperature gas sensing using the amorphous-InGaZnO (a-IGZO) thin films and UV irradiation assisted enhancement techniques. The a-IGZO thin films was grown by solution coating technique and post-annealed at 500 oC in air ambience. The characterization of ozone gas sensor under/without UV irradiation was carried out at room temperature at a range of ozone concentrations between 0.1 and 50 ppm in dry air. The UV irradiation was employed to enhance the ozone sensitivity as results of generating more carriers while a-IGZO surface exposures to the ozone molecular. This approach approves the sensing properties significantly with low working temperature, fast response, short recovery time and good selectivity compared to conventional gas sensors, making a-IGZO thin film potentially and more suitable for practical applications in environmental ozone monitoring. Furthermore, the electrical, microstructural and chemical inhomogeneity associated with polycrystalline semiconducting metal oxides (SMOs) were systemically studied, and the mechanism of room temperature and high sensitivity gas sensing are also explained. Keywords: gas sensor, UV irradiation, indium-gallium-zinc oxide (IGZO), Ozone adsorption.

Resume : Pr3+ doped CaTiO3 is an attractive phosphorus material which exhibit an ideal red emission around 610nm at room temperature. Therefore, several photoluminescence mechanisms have already been proposed. For the application toward fluorescent ink, morphology control of the particle is an important subject. In our laboratory, preparation of Pr3+ doped CaTiO3 particles is conducted by hydrothermal method using the precursor solution with citratoperoxotitanate, calcium chloride, and praseodymium nitrate, followed by calcination at 923K for 1h and the formation mechanism is investigated. FE-SEM observation revealed that spherical particle of 3μm in diameter was precipitated from the precursor solution adjusted pH=4 using HCl solution. It is also found that calcination of the precipitated particles resulted in the formation of perovskite structure without collapse of the spherical morphology indicating these spherical particles are stable against high temperature and some particles have hollow architecture. Zhao et al. reported that uniform mesoporous anatase-brookite biphase TiO2 hollow sphere were solvothermally obtained and proposed the formation mechanism based on Ostwald ripening. Though further investigation is needed, it is expected that same mechanism associated with the formation of our spherical particles.

Resume : As alternatives to PEDOT:PSS as hole transport layers (HTLs) in organic solar cells we have developed a low temperature method for solution processed NiOx thin films, and a growth method for very thin Ni(OH)2 flakes. In TQ1:PC70BM solar cells the power conversion efficiency improves from 5.3% to 6.1% when replacing PEDOT:PSS with NiOx thin films as HTL. Our method does not require high temperature annealing, and in fact, we were able to produce high performing NiOx HTLs using only UV-ozone treatment of a nickel formate precursor. Contact potential difference measurements revealed an increased work function for all UV-ozone treated NiOx films, leading to an improved energy level matching between the donor and the HTL. X-ray photoelectron spectroscopy revealed that a mixture of oxides and hydroxides is formed as a result of the UV-ozone treatment, while only annealing above 300°C produces any significant amount of NiO. Despite the absence of stoichiometric NiO in the low temperature processed HTLs, our devices with mainly nickel hydroxides show an enhanced performance compared to devices with PEDOT:PSS. From these results we suggest that very thin metal-hydroxide layers can be used as HTLs in organic solar cells with improved device stability as compared to metal-hydroxides. Therefore, we have also developed a synthesis for growth of thin Ni(OH)2 flakes using exfoliation of Ni(OH)2 crystals. These flakes are suitable for spin-coating of thin films in solar cell structures.

Resume : Vanadate materials are well proved matrices for luminescent rare earth (RE) ions because they satisfy high efficiency of transfer of excitation energy absorbed by matrix to the RE activators. The wide range of their applications have attracted significant research efforts to development of new vanadate compositions with improved characteristics depending on requirements of various practical tasks. The most attention for many-years was paid to study of the Eu-doped vanadates compositions. Indeed, the Eu3+ luminescent activators have demonstrated the best efficiency-to-cost ratio. At the same time, despite of the cost increasing some tasks could require improvement of spectroscopy characteristic s. Besides, investigation of vanadate compositions with various luminescent activators should help to better understand the processes of light absorption, energy transfer and radiation emission in vanadate hosts, in general. For such purpose, Sm3+ ions can be also considered as promising luminescent activator after the Eu3+ ions. Concentration rows of Sm - doped vanadate nanoparticles of the La1-xSmxVO4 (x < 0.3) compositions were synthesized by sol-gel and co-precipitation methods. Phase purity, morphology, IR and luminescence properties of the synthesized samples were studed. We have found that method of synthesis effects on all these parameters of the made vanadate samples. Origins of these effects are discussed in the paper.

Resume : This talk is about the new opportunities for solution based ferroic films, ranging from microelectronics to biological communication. Non-linear dielectrics display relevant special physical phenomena such as coupling strain and electric field (piezoelectric effect), temperature dependence of the polarisation (pyroelectric effect) and the presence of large polarisation in the absence of the electric field (spontaneous polarisation) that can be reversed by the application of an external electric field (ferroelectric effect). Non-linear dielectrics are therefore extremely useful from the application point of view; sensors, actuators, motors, transducers, temperature detectors, imaging and data storage, for a wide range of industries as automobile, aeronautics, computer, military, consumers and medical, are some of the examples. It is well known that optimized properties are commonly attained for so called “perfect” materials, i.e. single crystals, epitaxial films, highly dense and crystalline. Hence, the most common processing techniques are expensive, time consuming, involve high temperature budgets and exotic and expensive substrates, among other limitations. Here we advocate that if one considers some of the most current needs, of functional, flexible and biocompatible materials, produced via sustainable processes with direct-large-area integration, figures of merit do not require record values. As an example piezoelectric coefficients of bones up to 0.7 pC/N have been regularly reported and should be compared with 0.7 and 2.3 pC/N for different directions in quartz, and 600 pC/N in some piezoelectric ceramics. Consequently, there are new and unique opportunities for solution based processed ferroic thin films. This talk covers some of these new opportunities. We will start with the low temperature processed ferroic films via a novel solution method, our own proprietary solution-based Seeded Photosensitive Precursor Method that enables the processing of functional oxides under low-temperature conditions so that direct-large-area integration of active layers with flexible electronics becomes reality. The concept developed in collaboration between the University of Aveiro in Portugal and the Materials Science Institute of Madrid (CSIC) in Spain, was first demonstrated on the most important multifunctional oxide, PbZr1-xTixO3 (PZT) and very recently on lead-free multiferroic BiFeO3. Another example that elucidates our point of view will be presented. In the context of bone regeneration, it is important to have platforms that with appropriate stimuli can support the attachment and direct the growth, proliferation and differentiation of the cells. To respond to this situation we have been exploiting an alternative strategy for bone implants or repairs, based on charged mediating signals for bone regeneration, envisaged as a type of biological micro-electromechanical systems (BioMEMs), based on ferroelectric LiTaO3 (LTO) layers functionalized via electrical charging or UV-light irradiation.

Resume : The dependence of the electronic structure of ferroelectric/semiconductor interfaces on polarization of the ferroelectric has attracted great attention in the pursuit of developing functional thin film components for integrated circuit applications. Here, we report on the variability of the Schottky effect in solution processed Ba1-xSrxTiO3 films (BST, x=0, 0.5) grown on 0.5% Nb doped SrTiO3 substrates with top Pt electrodes (NSTO/BST/Pt). Films display leakage accompanied by varying degrees of hystereses in the current-voltage (I-V) measurements along with variation of Sr content. The I-V behavior of samples in the light of thermodynamic calculations coupled with equations of semiconductors, allows us to unambigously determine the electronic character of the defects and related band bending effects. Amplitude of the ferroelectric polarization is a function of composition which has a strong impact on leakage currents in forward bias while this effect is much weaker under negative bias. The latter occurs as any non-zero polarization pointing away from the NSTO substrate causes depletion of carriers at the NSTO side of the NSTO/BST interface along with an increase in the energy gap between the Fermi level and the conduction bands, thereby also reducing the bulk conduction through the film. Dependence of leakage currents on polarization direction could allow a non-destructive read-out route of polarization state in ferroelectric films much thicker than tunnel junctions.

Resume : The combination of complex functional oxides with the long-established Si-based complementary metal-oxide-semiconductor (CMOS) technology ensures the transfer of novel properties and additional electronic applications to the future devices. In this light, half-metallic ferromagnetic La0.7Sr0.3MnO3 (LSMO), ferroelectric BaTiO3 (BTO) and multiferroic BiFeO3 (BFO) represent appealing candidates to be integrated on silicon substrates for technological devices such as sensors, data storage, IR detectors, etc. However, the epitaxial growth of functional complex oxides on silicon is a complex task due to their chemical and structural dissimilarities, usually exclusively performed by high vacuum techniques. Here, we present high quality structural, morphological, and functional epitaxial thin films and multilayers obtained by an innovative combination route of Chemical Solution Deposition (CSD) and Molecular Beam Epitaxy (MBE) [1]. A detailed study of the chemical stability, crystallographic structure and interfaces between a SrTiO3 (STO) buffer layer growth by MBE and LSMO film grown by CSD enabled a perfect functional transfer. Epitaxial LSMO ultrathin films (less than 25 nm) are employed as bottom electrode to fabricate ferroelectric memories with BTO or BFO, deposited by MBE and CSD, respectively. We investigate the role of the mosaicity that modifies the nanostructure of the oxide multilayer system adding novel enhanced functionalities. As an example, the ferroelectric domains in BTO films can be reversed simultaneously by a bias voltage and applying a mechanical force [2]. Our synthetic route demonstrates the enormous potential of combining physical and chemical processes for the development of low cost oxide-based devices in silicon with extra functionalities. [1] J. M. Vila-Fungueiriño et al. Front. Phys. 3, 38 (2015). [2] A. Gómez et al. Small 13, 1701614 (2017).

Resume : We report on the solution-based synthesis of multiferroic thin films consisting of ferroelectric BaTiO3 and ferrimagnetic spinels MFe2O4 (e.g. M = Co, Ni). The films were prepared via spin coating of solutions of the respective metal cations in the unusual solvent mixture DMF/HOAc followed by appropriate decomposition and crystallization steps. As substrates platinum coated silicon wafers and SrTiO3 single crystals were used. A single coating step results in a film of roughly 30 nm thickness and different stacking sequences like bilayers or sandwich structures can be obtained. Using SrTiO3 substrates a (nearly) epitaxial growth can be realized and surprisingly even on Pt-coated silicon highly oriented ferrite films with a columnar growth were obtained. Phase evolution was monitored by XRD and Raman spectroscopy and the final composite films were further investigated via rocking curve and pole figure X-ray measurements and SEM in combination with EDX. Strong magnetic anisotropies were observed and magnetic and polarization hysteresis loops prove the simultaneous presence of ferrimagnetism and ferroelectricity.

Resume : Inkjet printing has recently gained increased attention as a promising fabrication technique for electronics. It allows for the deposition of patterned functional structures on various types of substrates without the use of cost-intensive lithography steps. Lead zirconate titanate (PZT) thin films are commonly used in many sensing and actuating devices. In this contribution, we will present a novel strategy for printing a PZT ink on a platinized silicon substrate. The PZT ink formulation is based on standard chemical solution deposition (CSD) processing of metal oxides. Adjunction of high viscosity and high surface tension co-solvents to the solution rendered it suitable for jetting. However, it is known that direct printing on platinum results in poor resolution due surface energy-driven ink spreading. Resolution can be improved by local modification of the surface energy with ink-repelling self-assembled monolayers (SAMs). We show that inkjet-printed SAM templates can be used for the deposition of PZT structures having a feature size in the sub-100 µm range and with control over the thickness of final layer. Our inkjet-printed PZT films with sputtered platinum top electrodes exhibit good ferroelectric characteristics (2 Pr = 32.2 µC/cm², ?? = 800, tan ? = 2.5%) and promising piezoelectric response, as strain butterfly loops with 0.1% strain at 500 kV/cm were measured.

Resume : Piezoelectric thin films on silicon have reached industrial maturity. In the quest for devices with extended functionalities integration of piezoelectrics with non-silicon substrates are needed. Glass offers capability to combine piezoelectricity and transparency. However, deposition of piezoelectrics on glass is not straightforward due to interface reactions, low glass transition temperature and the difference in thermal expansion coefficients. Therefore quality of the active layer depends strongly on the type of glass substrate and processing conditions. I will present our recent work on Pb(Zr,Ti)O3 (PZT) thin films deposited by Chemical Solution Deposition on fused silica substrates. Buffer layers have been employed to obtain crack-free and single-phase perovskite films by annealing at 700 °C. Transparent Al-doped ZnO interdigital electrodes have been designed and deposited by atomic layer deposition, while standard metal electrodes were used for comparison. State-of-the-art electromechanical response, which can be exploited in ultrasonic applications, will be presented and discussed. However, lower-temperature (max. ~550 °C) processing is required for deposition of PZT on low-cost commercial glass substrates. Combining nucleation layer PbTiO3 and chemical modification of transition-metal alkoxides we have already decreased the crystallization temperature to 600 °C. The approach will be discussed in detail in the contribution.

Resume : BiFeO3-based thin films exhibiting low leakage currents can be obtained, more or less effortlessly, by applying processing techniques such as PLD, CVD, MBE or RF sputtering, which allow a high degree of crystallographic control. Despite the effectiveness of these techniques, they all involve a high consumption of energy in terms of temperature and/or vacuum, so replacing them by sustainable processing alternatives represents a stimulating challenge. In this frame, a simple sol-gel plus spin-coating methodology is here proposed to prepare thin films of BiFeO3 co-doped with rare earth and titanium cations. Moreover, to further persist on the sustainability concept, the whole routine is conducted in aqueous media, hence avoiding the inherent toxicity of the organic solvents typically used in a conventional sol-gel method. As it will be described, attempts are conducted that eventually demonstrate how BiFeO3 thin films with interesting electrical properties can be feasible obtained with no need for a substantial energy supply.

Resume : In the first part of this talk, I will describe the block copolymer-templating synthesis of a series of large-pore mesoporous mixed-metal oxide thin films using an evaporation-induced self-assembly process and their characterization by imaging, diffraction and spectroscopic methods. In the second part, I will show that the general idea of combining nanomagnetism and electrochemical energy storage concepts can be applied to high-surface-area materials with spinel and perovskite structures, in particular mixed-valence manganese oxides and (transition) metal ferrites. When using such mesoporous thin films as electrodes in lithium-ion batteries or double-layer capacitors and carefully controlling the cutoff potentials, they allow for the intriguing possibility of tuning of magnetism at room temperature without compromising the lattice and pore structure.[1-4] [1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn and T. Brezesinski, Chem. Mater. (2014) 5745. [2] C. Reitz, C. Suchomski, D. Wang, H. Hahn and T. Brezesinski, J. Mater. Chem. C (2016) 8889. [3] C. Reitz, D. Wang, D. Stoeckel, A. Beck, T. Leichtweiss, H. Hahn and T. Brezesinski, ACS Appl. Mater. Interfaces (2017) 22799. [4] L. A. Dubraja, C. Reitz, L. Velasco, R. Witte, R. Kruk, H. Hahn and T. Brezesinski, ACS Appl. Nano Mater. (2018) DOI: 10.1021/acsanm.7b00037.

Resume : In the field of the synthesis and functionalization of inorganic nanoparticles (NPs) for biomedical applications, most researches aim at developing multifunctional theranostic NPs which can both identify disease states and deliver therapy and allow thus following the effect of therapy by imaging. The current challenge for iron oxide based NPs is the design of NPs able to combine in one nano-object both magnetic hyperthermia (MH) and MRI with the best efficiency in order to reduce the dose injected in the patient. IONPs are already commercially used as T2 contrast agent for MRI. The use of MH as therapy for cancer is closer to be a reality thanks to the positive results achieved by the clinical trials carried out by MagforceTM(Germany). Nonetheless, there is currently a need of improving NPs for MH. On that basis, NPs with different shapes were prepared by thermal decomposition of home-made iron stearate, functionalised with dendron ligands to achieve aqueous suspensions and proved suitable for in vivo injection. MH performance was found to be shape-dependent with octopod-shaped NPs exhibiting the highest SAR values. At the same time, their performance in MRI was investigated leading to relaxivity values, which were superior to those of commercial products like Resovist®. Cell response was studied as a function of NP concentration and morphology, as well as under MH treatment. The in vivo MRI and MH experiments have allowed evaluating their targeting potential, their biodistribution and their therapeutic properties. A start-up company is currently under construction.

Resume : Iron oxide magnetic nanoparticles (IONPs) are extensively studied for the new properties generated by their size, shape and composition but also because of their broad range of applications for which the magnetic properties of NPs must be tuned. NPs with given characteristics have then to be designed. Many efforts are put in the development of reproducible synthesis methods able to tune easily the characteristics of NPs, especially their shape which would add supplementary magnetic anisotropy energy. The thermal decomposition (TD) of an iron oxide precursor has shown to be the most suitable synthesis method to control the NPs shape. Nevertheless, this control is not trivial and the current strategy involves the addition of various ligands and the precise control of reaction parameters (heating rate, nature of solvent ?). However one parameter is frequently forgotten: the iron precursor itself through its structure and stability. Thus we?ve synthesized different iron stearates by varying the iron oxidation degree and the hydration rate. After fine characterization (TGA, XRD, SAXS, IR(T)...) the role of precursor structure has been related to their decomposition kinetics and to NPs characteristics. The influence of ligands on the shape of NPs has been done with different iron precursor structures and showed a link between the precursor structures with the obtained shape. Such study permitted thus the synthesis of several anisotropic shapes such as cubes, octopods and plates.

Resume : Owing to their size and shape dependent properties, magnetic nanoparticles (NPs) are covering a wide range of applications. A step further would be to design new functional oxide-based hybrid materials with controlled nanostructure to tune their magnetic properties. As Fe3O4 is a non-toxic and cheap material, it could be interesting to increase its magnetic anisotropy for spintronic applications in order to solve data storage problems. Here, we report the original synthesis of a newly metallic oxide-based hybrid functional material: Fe3O4@CoO@Fe3O4 core@shell@shell NPs. They are synthesized through a succession of thermal decompositions where an inorganic ligand ensure their colloidal stability in common organic solvent. This hybrid system showed a high magnetic stability due to an exchange bias (EB) coupling property that increase the magnetic anisotropy through the coupling of antiferromagnetic and ferrimagnetic phases. However, some surprising magnetic properties lead to investigate further the nanostructure of such NPs with advanced characterization techniques. Thus, EELS, EFTEM, XMCD or p-SANS were used to get crucial information about the chemical composition of the interface which is known to be responsible of the magnetic properties.

Resume : Printed organic field-effect transitors (OFETs) have been considered for many novel applications towards large area and flexible electronics, since they can enable pervasive integration of electronic functionalities in all sorts of appliances, their portability and wearability. Applications are countless: from personal devices (e.g. wearable health monitoring devices) to large-area sensors (e.g. electronic skin, bio-medical devices), and smart tagging of products with radio-frequency identification tags. However, printed OFETs fabricated with scalable tools fail to achieve the minimum speed required for example to drive high-resolution displays or to read the signal from a real-time imager, where a transition frequency (fT), i.e. the highest device operative frequency, above 10 MHz is required. In this contribution I will present effective strategies to increase fT in polymer devices by combining only printing and laser-based direct-writing techniques. By exploiting the self-assembly of model conjugated polymers, such as naphthalene diimide based co-polymers, highly controlled printed anisotropic thin films with excellent transport properties are demonstrated. Shear-aligned thin films with a uni-axially oriented functional surface are realized. This approach produces a marked increase in FET mobility and anisotropy, plus superior performance uniformity with respect to the spin-coating deposition. The simple adoption of this fast coating approach allows to strongly enhance the highest operational frequency of FET devices, achieving a transition frequency of 3.3 MHz. By combining printing and laser-based direct-writing techniques, additional strategies to boost the transition frequency of polymer based devices can be pursued. First, by combining inkjet printing and femtosecond laser ablation to obtain small channel lengths, all-polymer FETs operating in the MHz regime can be fabricated on plastic without the use of any mask. In particular, an engineered layout of the contacts allows to achieve a transition frequency of 4.9 MHz. Alternatively, narrow, micron-scale metallic electrodes can be sintered on plastic through femtosecond laser sintering. The combination of such electrodes with fast-coated polymers allow to achieve the higher transition frequency for a mask-less fabricated polymer transistor to date, reaching 20 MHz. The use of multi-layered dielectrics, combining low-k and high-k materials, allows to reduce the operating voltages of printed transistors on plastic below 10 V. In this context we demonstrate simple integrated circuits capable of operating well below 10 V, and therefore compatible with thin-film batteries or energy harvesting devices.

Resume : The current best performing p-type transparent conducting oxides are highly crystalline, deposited at high temperatures; incompatible with the drive to low cost flexible electronics. We investigated a nanocrystalline CuxCrO2, deposited at low temperatures upon a flexible polyimide substrate. The as-deposited film without post annealing has an electrical conductivity of 6 S cm?1. We demonstrate that this p-type transparent oxide retains its excellent electrical conductivity under tensile strain, withstanding more than one thousand bending cycles without visible cracks or degradation in electrical properties. In contrast, compressive strain is shown to lead to immediate delamination and reduction in conductivity which we attribute to a de-lamination of the thin film from the substrate.

Resume : The possibility to deposit oxide materials by low cost techniques such as inkjet printing, as an alternative to silicon technology, has drawn tremendous interest on solution processible materials for electronic applications. However, high processing temperatures are still required. To overcome this issue solution combustion synthesis has been recently pursued. By taking advantage of the exothermic nature of the reaction as a source of energy for localized heating, precursor solutions can be converted into oxides at lower process temperatures. Solution combustion synthesis has been applied to produce semiconductor oxides thin films based on combinations of ZnO, In2O3, SnO2, and for high ? dielectrics (Al2O3 and HfO2). All of which are required for numerous electronic devices and applications such as fully oxide based TFTs. The properties of produced thin films are highly dependent on the precursor solution characteristics and degradation/oxide formation process. Recently, to further enhance solution processed materials? properties alternative methods have been exploited, such as UV irradiation and laser induced solution combustion. We demonstrate that high performance devices are obtained by fine tuning processing parameters (organic fuel, solvent, temperature) and optimizing degradation/oxide formation process by UV and laser irradiation. R. Branquinho, et al. (2016). K.G. Konstantinos & J. Skvaril (Eds.), InTech. https://doi.org/10.5772/64761

Resume : High-speed Schottky diodes fabricated on mechanically flexible substrates are highly desirable as front-end rectifiers in mobile phone communication systems, wireless sensors and wearable electronics. Usually high performance, in terms of cut-off frequency and output voltage or power, has to be compromised to enable fabrication on plastic substrates. To tackle this manufacturing challenge, solution-processed metal oxide semiconductor thin films have appeared as a viable alternative to conventional semiconductors. Herein, we first apply adhesion lithography (a-Lith), an innovative nanopatterning technique, to fabricate asymmetric co-planar metal electrodes separated by a < 15 nm nanogap on arbitrary size and type substrates. Then, we combine this advantageous co-planar geometry with functional metal oxide semiconductors processed from solution at low, plastic-compatible temperatures and demonstrate high rectification ratio diodes that can drive high currents in a very small active area. It will be shown that the extreme downscaling of key device dimensions leads to high-speed diodes with cut-off frequencies well within the GHz regime. Next, detailed analysis of the current?voltage (I?V) and capacitance?voltage (C?V) characteristics will prove how effective doping of the metal oxide semiconductor, thin multilayer structures and metal oxide dielectric encapsulation result in radiofrequency (RF) rectifier performance optimisation and improved device stability. This ideal combination of using a-Lith as a simple, low-cost and high-throughput nanogap electrode fabrication technique with intelligent material and device engineering concepts showcases the potential for developing high performance flexible RF devices.

Resume : Lately resistive switching memories (ReRAM) have been attracting a lot of attention due to their possibilities of fast operation, low power consumption and simple process fabrication. To decrease the associated costs even more, in this work the ReRAM is developed from a solution-based aluminium oxide (Al2O3) in a combustion synthesis. The ReRAM functionality of the Al2O3 is tested for monolayer and bilayer device structures. A decreased oxygen/aluminium ratio on the surface of the bilayer film compared to the monolayer is observed by XPS. Modulating the oxide interface/oxide in a bilayer ReRAM results in the operational yield of 100 %. Both bipolar and unipolar resistive switching behaviour is obtained depending on the current compliance of the set process. In addition, the resistive states are altered by applying different reset voltages. This opens the opportunity of a multilevel cell operation (MLC) programming. The retention time up to 10,000 s and high endurance cycles for each resistance state are obtained. Temperature analysis of various resistance states reveals different doping levels from a degenerate doping (metallic-like) for lower resistance states to a moderate doping for higher resistance states. The optimized bilayer structure is stacked with transparent electrodes, indium-tin oxide at the bottom and indium-zinc oxide on top. These devices are potential candidates for the integration of ReRAM into cost effective System-On-Panel technology for transparent display technology.

Resume : Recently, oxide based thin film transistors (TFTs) have attracted considerable attention for next generation flat panel displays such as LCDs and OLEDs, due to their outstanding electrical properties. Although an In-Ga-Zn-O (IGZO) is widely accepted as a promising channel material for TFT, the instability of the TFT under negative bias with illumination stress (NBIS) is one of the remaining problems. In this research, we discuss how to suppress the instability and the mechanism of the instability. A 50nm IGZO film were deposited onto the n-type crystalline silicon with 100nm thick of silicon dioxide. After forming Cr source-drain electrodes, a 20nm SiOx passivation was deposited. High performance and highly-stable IGZO TFT have been achieved by annealing upside down or with covered with a glass substrate. Field effect mobility and subthreshold swing were significantly improved compared with the TFT annealed at 350 degree C in air for one hour. In addition, degradations under NBIS was almost suppressed. We found that the mobile oxygen in the IGZO is strongly associated with the reliability.

Resume : Inkjet printing has risen as a promising method for the low cost and large area deposition of functional thin films for electronic devices. However, due to the high post deposition annealing (PDA) temperature of the printed layers, the use of this method is still limited to high Tg substrates (Tg>250oC). To reduce the PDA temperature, a deep UV (DUV) irradiation has been proposed as an effective method and to the date, the lowest processing temperature of 150oC has been achieved for the DUV treated layers. This study aims to achieve a printed dielectric layer for oxide based thin films transistors (TFTs) deposited on temperature sensitive polymer substrates. A high dielectric constant and a leakage current density as low as 10^-9 A/cm2 at 1MV/cm effective field are obtained by controlled doping of Aluminium oxide with Yttrium (Y:Al2O3). Yttrium oxide is a high-k metal oxide with a dielectric constant of ~18, whereas the aluminium oxide is known as an effective blocking layer for the current flow. Y:Al2O3 layers are deposited via inkjet printing, and a DUV treatment without intentional heating is applied for curing and densifying the printed layers. Printed layers are characterized electrically via I-V and C-V methods to observe the leakage current density and the dielectric constant of the layers, respectively. The performance of the printed dielectrics will be compared with their vacuum based deposited counterparts in flexible TFTs fabricated on polyimide substrates.

Resume : In this work we compare atomic layer deposited and solution-processed yttrium oxide (Y2O3) passivation thin-films for solution-processed indium based metal-oxide thin-film transistors (MOTFTs). Due to the sensitivity of metal oxides to several gases and adsorbates, especially oxygen and water, the transistors should be encapsulated for long-term stability. Here, we study the bias stress stability of transistors passivated with (a) solution-processed octadecylphosphonic acid (OPA) treated at T = 120 °C, (b) atomic layer deposited Y2O3 (ALD-Y2O3) prepared at T = 200 °C and (c) solution-processed (sol-gel)-Y2O3 converted at T = 350 °C in order to see, if low-cost fabrication of large-area Y2O3 films can compete with cost-intensive vacuum processes like atomic layer deposition. The transistor parameters are not affected by a passivation layer in all cases and are comparable for all MOTFTs prior to the stress measurements (µ ? 2 cm2V-1s-1, Ion/off ? 108). In contrast to Y2O3-passivated MOTFTs, the transistors passivated with OPA show a significant hysteresis. The cut-off voltage of the transistors shifts during positive (negative) bias stress by +12 V (?3 V) for OPA-passivated transistors, +6 V (?4 V) for transistors passivated with sol-gel-Y2O3 and +3 V (±0 V) for transistors passivated with ALD-Y2O3. Thus, Y2O3 clearly enhances the stability of the transistors and the solution-processed passivation layer can nearly compete with the cost-intensive ALD film.

Resume : Distributed X-ray radiation dosimetry is crucial in diverse areas such as nuclear waste management, radiotherapy or personal protection devices. Most current sensitive wearable dosimeters employ an optical readout after exposure and do not provide real-time information. Here we present novel thin film flexible transistors (TFTs) fabricated on plastic substrates, that behave as real time direct X-ray detectors. They are based on high mobility oxides, and show a marked quantitative shift in threshold voltage of up to 5.5 V/Gy upon exposure to ionizing radiation. The transistors employ Gallium-Indium-Tin-Oxide as semiconductor and a multilayer dielectric containing layers of Silicon Oxide and Tantalium Oxide. Our measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high-Z dielectric. The high mobility combined with a steep sub-threshold slope of the transistor allows for fast, reliable and ultra-low power readout of the deposited radiation dose. Moreover, the observed order of magnitude variation in transistor channel impedance upon exposure to radiation makes it possible to employ a low-cost, passive RFID sensor tag for its readout. In this way we demonstrate a passive, programmable, wireless sensor that reports in real-time the excess of critical radiation doses. It is noteworthy that the preliminary studies we have carried out on the radiation hardness of the here described thin oxide transistors, indicate that transport properties of the oxide semiconductor do not show relevant radiation damage effects [1] [1] T. Cramer, A. Sacchetti, M. T. Lobato, P. Barquinha, V. Fischer, E.Fortunato, R.Martins and B.Fraboni., Adv. Electron. Mater., vol. 2, no. 7, pp. 1?8, 2016.

Resume : We demonstrate all transparent vertical Schottky barrier (SB) transistors and logic gates based on reduced graphene oxide (rGO)-metal oxide-metal heterostructures and ion gel gate dielectrics via all printing process. The vertical SB transistor structure was formed by (i) vertically sandwiching a printed indium-gallium-zinc-oxide semiconductor layer between rGO (source) and indium-tin-oxide (drain) electrodes and (ii) employing a separate coplanar gate electrode bridged with the vertical channel through an ion gel. The channel current was modulated by tuning the Schottky barrier height across the rGO-IGZO junction under an applied external gate bias. The high specific capacitance of the ion gel gate dielectrics enabled the Schottky barrier height at the rGO-IGZO junction to be modulated by 0.5 eV using a voltage below 2 V. The resulting vertical devices showed high on-off current ratios (> 105) at low voltages in ambient condition. The simple structure of the unit transistor enabled successful fabrication of low-power logic gates based on assemblies of devices such as the NOT, NAND, and NOR gates on a transparent substrate. The simple, scalable printing process of all layers of the SB transistor.

Resume : Development of active and robust metal-composite electrocatalyst for PEM Fuel Cells, supercapacitors and hydrogen evolution reaction (HER) remains one of the biggest challenges today in the effort to move towards a green and sustainable environment. In recent years, there are numerous reports of 1D carbon materials and 2D transition metal dichalcogenides (TMDs), mainly MoS2, as complementary electrocatalyst, having among the highest electrochemical activity. In this review, we will give a short summary on our past achievements of fabricating various hybrid 1D-2D structures using solution synthesis, as well as the current research status on various composites such as Ag nanowires, NiOOH, CoP, CoSe2 and MoS2 with direct applications in PEM Fuel Cells, Supercapacitors and HERs.

Resume : Plasmonic hybrid nanostructures assembling nanoparticles (NPs) of noble metal (Ag, Au, Pt) and metal-oxide semiconducting nanowires (NWs) combine the localized surface plasmon resonance (LSPR) of the NPs with the photochemical properties of NWs. This synergetic coupling was recently exploited in many domains involving light trapping and electromagnetic field enhancement such as photocatalysis for pollutant and bacterial destruction, and surface enhanced Raman scattering (SERS). Recently we have designed two new plasmonic nanostructures via a facile two-step procedure. Firstly, ultra-thin photosensitive silver molybdate NWs were obtained from novel solution-based synthesis routes in ambient pressure [1][2]. Secondly, metal silver NPs were photogenerated at the surface of the NWs under UV-light. In stark contrast with other reported methods, this solid-state alternative photodeposition process does not require a high-power photoexcitation and a solid-liquid interface, that allows a more precise control of the NPs size distribution. The plasmonic activity of the two nanocomposites has been investigated by a combination of electron energy-loss spectroscopy (EELS), UV-vis and Raman spectroscopies. They were demonstrated as efficient visible-light driven photocatalysts for the degradation of Rhodamine B dye solution and SERS active substrates for the detection of 2,2?-bipyridine. [1] K. Hakouk et al., Inorg. Chem. 2013, 52, 6440. [2] H. Serier-Brault et al., 2018, Submitted.

Resume : Gold (Au) nanoparticles (NPs) exhibit unique chemical and physical properties which already gained a strong interest for electronic, magnetic, and as well as catalytic applications [1]. The use of Au NPs as catalyst for degradation of organic pollutants have been shown in various studies. On the other hand, one of the main challenges is controlling the stability of Au NPs against the agglomeration in aqueous media. The formation of agglomerates reduces the catalytic efficiency significantly and mostly metal oxides (TiO2, ZnO, CeO2 etc.) are used to support Au NPs to improve their stability [2]. In addition, metal/metal oxide interfaces provide superior catalytic properties owing to the electron confinement effects. In this study we prepared Au-ZnO hybrid catalysts through a controlled reduction synthesis and after a detailed structural and compositional analysis (SEM, TEM, XPS) we evaluated their catalytic properties. Au-ZnO hybrid structures exhibited an enhanced catalytic performance in comparison to pure ZnO. The electron relay effect seems to be the dominating mechanism at lower Au loading concentrations (4-5%), which was disturbed at higher Au loading (>8%) [1] Vincenzo Amendola, Roberto Pilot, Marco Frasconi, Onofrio M Maragò , Maria A Iatì, J. Phys. Condens. Matter. 29 (2017) 203002. [2] S. Veziroglu, M. Kuru, M.Z. Ghori, F.K. Dokan, A.M. Hinz, T. Strunskus, F. Faupel, O.C. Aktas, Mater. Lett. 209 (2017) 486?491.

Resume : Nanostructures with high surface area are highly desirable for catalysts for oxygen evolution reaction (OER).1 Strategies to increase the catalytic activity are to decrease the size of the catalyst particles and/or to make them porous.2,3 However, ultrasmall nanoparticles and porous structures can be difficult to synthesize, might be poisoned by stabilizing ligands and templates, or are prone to sintering and aggregation. It remains challenging to create interconnected pores of only several nanometers. While electrochemical anodization has been used to create porous materials for applications in electronic devices, photocatalysis, capacitors and hydrogen evolution catalysts,4 they are rarely applied to make porous OER catalysts. Herein we report that the electrochemical anodization of precursors of such as perovskite hydroxides and selenides can form hierarchical porous nanostructures under mild conditions, leading to catalysts with extramely high catalytic activity.5,6 Precursors can be easily synthesized by wet-chemical methods and directly grown on substrates. Crystal defects of oxygen vacancy in perovskite hydroxides appears to be essential for the initiation of the formaiton of porous strucutres. Perovskite hydroxides with more oxygen vacancies underwent etching of higher degree, resulting in more porous structures and thus higher OER catalytic activity. Metal oxides derived from nickel iron selenides catalyzed OER with an overpotential of only 195 mV for a current density of 10 mAcm-2. This is until now the most active single-phase OER catalyst in alkaline solutions. Our work demonstrates how such facile electrochemical anodization can be applied to develop better catalytic materials. The precursoring approach described here might be applicable for the synthesis of other metal oxide-based nanomaterials. 1) N. T. Suen, S. F. Hung, Q. Quan, N. Zhang, Y. J. Xu, and H. M. Chen, Chem. Soc. Rev. 2017, 46, 337-365. 2) A. J. Esswein, M. J. McMurdo, P. N. Ross, A. T. Bell and T. D. Tilley, J. Phys. Chem. C, 2009, 113, 15068?15072 3) J. Rosen, G. S. Hutchings and F. Jiao, J. Am. Chem. Soc., 2013, 135, 4516?4521 4) Y. Yang, G. D. Ruan, C. S. Xiang, G. N. Wang and J. M. Tour, J. Am. Chem. Soc., 2014, 136, 6187?6190. 5) F. Song, K. Schenk, and X. L. Hu*, Energ. Environ. Sci. 2016, 9, 473-477. 6) X. Xu+, F. Song+,* and X. L. Hu,* Nat. Commun. 2016, 7, 12324. (*Corresponding author, +equal contribution).

Resume : The novel Al-doped ZnO/SnO2 heterostructured arrays have been grown on the glass substrates by a facile wet chemical and hydrothermal methods, respectively. The concentration of SnO2 precursor can be used to control the different sizes and shell thicknesses of ZnO/SnO2 heterostructured arrays. The morphology, crystal structures, and optical property of ZnO/SnO2 heterostructured arrays were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The Al-doped ZnO/SnO2 heterostructured arrays have excellent photocatalytic efficiency, which are ascribed to increase a higher surface-to-volume ratio and better stability against aggregation, which exhibit excellent photocatalytic activity rather than commercial TiO2 or ZnO nanopowders under a 10 W UV light irradiation. The Al-doped ZnO/SnO2 heterostructured arrays provide a facile, low cost, high surface-to-volume ratio, high photocatalytic efficiency, and high reusability, which shall be promising applications in photocatalysis and relevant areas. In addition, the appropriate Ag sputtering durations on the ZnO/SnO2 heterostructured arrays were optimized to yield the greatest surface-enhanced Raman scattering effect in the rhodamine 6G molecule. The ZnO/SnO2/Ag heterostructured arrays provide a facile, high enhancement, low detection limit and low cost fabrication, which shall also be of significant value for practical applications of other SERS sensing systems.

Resume : Graphene-metal/metal oxide composites combine excellent electrical conductivity and mechanical strength of graphene with inherent catalytic activities of metal/metal oxides. These composites exhibit significantly higher catalytic/electrochemical performance than their individual counterparts because of the ?synergistic effect? between graphene and metal/metal oxides. We have utilized different techniques to produce graphene-metal or metal oxide composites in different forms like aerogels, self-standing membranes or thin films. The composites were used in catalytic reactions, or supercapacitor applications. For example, Pt nanoparticles were dispersed onto graphene aerogel through ex-situ deposition techniques. The resulting high surface area aerogels decorated with Pt nanoparticles showed excellent electrochemical surface area and ORR performance outperforming the porous graphene supported Pt in the literature. On the other hand, MnOx nanoparticles were electrodeposited onto self-standing graphene papers at room temperature. These composite papers annealed at different temperatures exhibited excellent cyclic stability in Cyclic Voltammetry measurements. In addition, we have revealed the structure- property relation in thin films of graphene and iron oxide nanoparticles deposited with layer-by-layer technique. Herein, I will demonstrate results from our work on graphene oxide aerogels or papers decorated with different metals or metal oxides.

Resume : We have investigated the effects of barium deficiency on structural magnetic and magnetocaloric properties of La0.6Nd0.1Ba0.3-x?xMn0.9Cr0.1O3 (x = 0, 0.05 and 0.1) manganites prepared using the solid-state reaction. All the studied samples crystallize in the orthorhombic structure phase with Pnma space group. Magnetization versus temperature showed that samples exhibit a second-order paramagnetic (PM) to ferromagnetic (FM) transition with a decrease of the Curie temperature (TC) from 275 K for x= 0 to 235 K for x = 0.1. The increase of barium deficiency leads to the decrease of the maximum magnetic entropy change |??S?_M^max | and RCP values from (4.40 J.kg-1 K-1 and 262.94 J.kg-1, for x= 0) to (2.78 J.kg-1 K-1 and 159.41 J.kg-1, for x= 0.1) for an applied magnetic field ?0H= 5 T. These values are compared favorably with those of some others reported manganites, making our samples promising candidates for the magnetic refrigeration technology.

Resume : We developed a facile method for treating polyimide-based organic gate insulator (OGI) surfaces with self-assembled monolayers (SAMs) by introducing metal-oxide interlayers, called the metal-oxide assisted SAM treatment (MAST). To create sites for surface modification with SAM materials on polyimide-based OGI surfaces, the metal-oxide interlayer, here amorphous alumina (a-Al2O3), was deposited on the organic gate insulator using spin-coating via a rapid sol–gel reaction, providing an excellent template for the formation of a high-quality SAM with phosphonic acid anchor groups. The SAM of octadecylphosphonic acid (ODPA) was successfully treated by spin-coating onto the a-Al2O3-deposited OGI film. After the surface treatment by ODPA/a-Al2O3, the surface energy of the KPI thin film was remarkably decreased and the molecular compatibility of the film with an organic semiconductor, Ph-BTBT-C10, was increased. Ph-BTBT-C10 molecules were uniformly deposited on the treated gate insulator surface and grown with high crystallinity, as confirmed by AFM and XRD analysis. The mobility of Ph-BTBT-C10 thin-film transistors (TFTs) was approximately doubled after the surface treatment. The surface treatment of a-Al2O3 and ODPA significantly decreased the threshold voltage from -21.2 V to -8.3 V by reducing the trap sites in the OGI and improving the interfacial properties with the OSC. We suggest that the MAST method for OGIs can be applied to various OGI materials lacking reactive sites using SAMs. It may provide a new platform for the surface treatment of OGIs, similar to that of conventional SiO2 gate insulators.

Resume : We demonstrate for the first time epitaxial growth of metal oxide thin films by liquid phase deposition (LPD) method. LPD is a soft chemical technique to grow highly uniform metal oxide thin films based on the slow hydrolysis of metal fluoride complexes at mild conditions. As an example ferroelectric PbTiO3 perovskite thin films with 150 nm thickness were grown on (001) Nb-doped SrTiO3 substrates. High resolution X-ray diffraction (HR-XRD) studies showed that films are epitaxial with (001) orientation. The Phi-scan of the film and substrate around (102) revealed a fourfold symmetry for both. HR-XRD reciprocal space map (RSM) around (103) of film and substrate revealed that films are fully strained with a compressive strain. The lattice constants calculated from the horizontal and vertical peak positions are; a = 0.403 nm and c = 0.407 nm. The topography of the films was studied by an atomic force microscope (AFM). Topography studies showed that films are highly uniform with densely packed elongated grains developed along the (100) and (010) orientations. Ferroelectric domain configuration was investigated by a piezoelectric force microscope (PFM). Two types of 180 and 90 degrees ferroelectric domains were observed. Epitaxial compressive strain is responsible for the formation of 90 degree domains. The strain forces electrical dipoles to rotate away from the normal. Our studies showed that high quality and highly uniform metal oxide films such as PbTiO3 could be grown on substrates by LPD, a simple and low cost method.

Resume : The BiFe0.5Cr0.5O3 double perovskite is predicted from theoretical calculations to be a multiferroic with a large ferroelectric polarization and magnetization (80 microC/cm2 and 160 emu/cm3 at 110 K), and a low bandgap (Eg = 2.0 eV). Based on these properties, applications in spintronics and photovoltaics are envisaged for these materials. However, the stabilization of this phase in thin film form is scarcely reported; BiFe0.5Cr0.5O3 films have been successfully attained by pulsed laser deposition [1]. This work explores the preparation by solution deposition of BiFe1-xCrxO3 thin films with x values between 0 and 50 mol%. Bi(III), Fe(III) and Cr(III) complexes were synthesized as precursors by the reaction of the metal cations with alkanolamine and/or dihydroxy alcohol ligands [2]. The synthesized solutions were stable and homogeneous, making possible the crystallization of BiFe1-xCrxO3 thin films at 500ºC on silicon and SrTiO3 substrates, for low chrome contents. For the stabilization of the BiFe1-xCrxO3 double perovskite with x > 0.12, original processing approaches producing a controlled stress in the sample during film crystallization have been tested. The crystal structure, ferroelectric and optical properties of these films are studied, determining the stability limit for the formation of BiFe1-xCrxO3 films by the solution deposition methods here developed. 1. Nechache et al., Nature Photonics, 2015, 9(1), 61. 2. Bretos et al., Chem.Soc.Rev., 2018, DOI: 10.1039/c6cs00917d

Resume : One-dimensional single crystalline cobalt rhodium oxide (Co2RhO4) nanotubes were successfully synthesized by simple and low-cost electrospinning method via one step annealing process using precursor of cobalt oxide (Co3O4) and rhodium oxide (Rh2O3) for the first time. Particularly, cobalt rhodium oxide (Co2RhO4) nanotubes are the single cubic phase crystalline structure without any minor crystalline phase proved by field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM and TEM data indicate that the electrospun nanofibers of cobalt rhodium oxide are formed with the hollow tube-like shape that has an outer diameter of about 100 nm and an inner diameter of about 80 nm. In addition, the tubular structure of crystalline Co2RhO4 represents highly efficient electrocatalytic activity comparable to commercial Ir and RuO2 catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) toward future electrochemical applications.

Resume : Due to their high dielectric constant, their wide band gap and their good thermal and chemical stability on Si, hafnium silicates (HfSiOx) are often presented as promising high dielectric materials to replace SiO2 in CMOS devices. Moreover, they offer a useful crystal-like environment suitable for the embedment of rare earth ions which give them a particular interest for the development of new optical devices. However, the structure of HfSiOx thin layers, which affects the optical properties, depends on fabrication parameters and requires deeper investigations. In the present work, structural and optical properties of Pr3+ doped HfSiOx layers fabricated by radio-frequency magnetron sputtering were investigated as function of annealing temperature. Photoluminescence measurements evidenced a maximum of luminescence intensity at 487 nm for the sample annealed at 1000°C. To understand the evolution of the luminescence, the microstructure has been investigated by Atom Probe Tomography and Transmission Electron Microscopy. These experiments highlighted a spinodal decomposition of the matrix with a phase separation between Si-rich and Hf-rich phases after annealing treatment. Deeper analyses of chemical structure have evidenced the formation of a SiO2 phase and a HfO2 cubic crystalline phase. Finally, it has been shown that Pr3+ ions tend to be located into HfO2 cubic phase. These results allowed us to correlate the structure of doped HfSiOx films to their optical properties.

Resume : The depletion of fossil fuels and the continuous rise of CO2 concentration in the atmosphere are two serious problems, which can be solved with one approach: photocatalytic conversion of CO2 to solar fuels, i.e., artificial photosynthesis. Most of the CO2 reduction experiments are currently performed in liquid phase, where the photocatalyst is deposited onto porous structures or used in the form of films or powders. Here we propose an alternative approach: performing the reaction in the gas phase in the presence of a monolithic porous photocatalyst. This approach makes it possible to tailor not only the composition of the photocatalyst but also its three-dimensional architecture. We produced macroscopically sized aerogel monoliths by controlled destabilization of nanoparticle dispersions, which were synthesized by a non-aqueous sol-gel route. TiO2 nanoparticle-based aerogels show a highly selective photoconversion of CO2 to methanol. However, the fast electron-hole recombination and the photocatalytic activity only in the UV range of TiO2 prevent its methanol production rate from reaching more than one µmol g-1 h-1. The incorporation of different metallic or semiconducting co-catalysts into the aerogels improved the efficiency of the CO2 reduction process. More than five times higher methanol production rates could be measured (with a maximum rate of 5.81 µmol g-1 h-1).

Resume : Interfacial exchange coupling in heterostructures, engineered in atomic scale is an essential feature of modern electronic devices [1].The exchange bias (EB) effect in coupled FM (ferromagnetic)/AFM (antiferromagnetic) systems has been studied extensively because of its critical role in spintronics based devices and intriguing spin physics [2]. Here 20 u.c. thick SrRuO_3 (SRO) thin film, 100 u.c. thick PrMnO_3 (PMO) thin film and a series of superlattices with [17-u.c.(unit cell) SRO/n(= 3,4,…16)-u.c. PMO ] bilayer configurations were prepared by repeating the bilayer for 15 times by pulsed laser deposition technique. The crystal structure and interfacial magnetic coupling of the artificially fabricated superstructures have been investigated. The desired growth of all the superlattices have been verified by θ-2θ x-ray diffraction (XRD) patterns. The observed (001) Bragg’s reflection with three orders of satellite peaks and Kiessig fringes on either side of the STO peaks suggest the presence of long-range periodicity, epitaxy and good crystallinity. The simulated XRD profile was obtained using DIFFaX program [3], which is in good agreement with the measured XRD with respect to the position of Bragg’s peaks and their relative diffracted intensity. The crystal structures of the thin films and the superlattices were further studied from their reciprocal space mapped along the four ϕ-orientations. The reciprocal space mapping (RSM) was constructed from the Bragg’s reflection measurements consisting of 2θ-ω coupling scans in (103)_pc for different ω values for the thin films and all the superlattices [4]. The diffraction peaks associated with the substrate and the film or superlattice occur at the same value of ω, indicating that the film or superlattice is completely strained i.e. pseudomorphic. However, the transverse scattering vectors corresponding to the diffraction peak positions of the substrate and film or superlattice are different. The diffraction peak positions along the 〈103〉_pc of {103}_pc of SRO are different though that of the substrate is same, which suggest the stabilization of distorted orthorhombic SRO on STO. In contrast, the angular positions of the Bragg’s diffraction along the 〈103〉_pc of {103}_pc of PMO and 0 th order superlattice peak of the superlattices are same, which indicate that the PMO and the superlattices have tetragonal phase even though the SRO and PMO crystallize in orthorhombic structure in bulk [4]. The M(T) of the superlattice with n = 3 indicates that the paramagnetic phase transforms into the ferromagnetic phase at temperature Tc ≈188 K, corresponds to the Tc of SRO. The spontaneous magnetization of Mn ions start contributing around the temperature ≈130 K(Tc* : transition temperature corresponds to PMO), then the magnetization increases up to ≈114 K (TN), followed by the decrease of magnetization down to the lowest temperature. The decrease in magnetization indicates the presence of the antiferromagnetic coupling at the interfaces between the SRO and PMO. Similar M(T) with different values of Tc,Tc* and TN are observed for the superlattices with n = 4 and 5. For the superlattices with n≥6, the TN is absent due to the weakening of AFM coupling strength and the increase of the ferromagnetic volume. At temperatures below TN, the sharp decrease in magnetization of the superlattices with n < 6 compared to the M(T) of La0.7Sr0.3MnO3(LSMO)-SRO [4] and orthorhombic Pr0.7Ca0.3MnO3(PCMO)-SRO [4] superlattices indicates the presence of strong in-plane antiferromagnetic coupling due to the observed tetragonal structure in the RSM, which is developed after the rotation of octahedra in the ab-plane around the c-axis from its cubic symmetry [4]. Here, the Ru-O-Mn bond angle becomes nearly equal to 180° along the growth direction. The superexchange between two half-filled d-orbitals of Mn^(3+) and Ru^(4+) mediated by oxygen in a 180° bond is strongly antiferromagnetic from the first Goodenough-Kanamori rule [4]. The ZFC M(H) measured at 20 K with field range ±7 T reveal a two-step magnetization reversal mechanism with magnetically soft PMO layer reversing first followed by the hard SRO layer. The observed lower value of Hc = 0.008 T for the superlattice with n = 3 compared to that of the PMO thin film indicates that the spin of Mn ions switch at the lower field than the expected Hc = 0.018 T due to the favourable antiferromagnetic coupling energy [4]. As the external magnetic field increases above the first switching field, Ru spins overcome the interfacial exchange coupling lead to the second switching at a very high field (~3 T) compared to the Hc of SRO (~0.18 T) [4]. The exchange coupling between the SRO and PMO in these superlattices was further studied from the ZFC and FC M(H) measured at 20 K with field range ± 0.5 T. After cooling the superlattices with +ve Hcool (cooling field) < Hcool^s (switching field) to lowest temperature, delta (the angle between Ru and Mn spins ) becomes> 90°. During the hysteresis loop measurement on decreasing the field from 0.5 T to – 0.5 T, spin of the Mn and Ru ions at the interfaces will rotate towards decreasing field direction, which is opposed by the antiferromagnetic exchange coupling. The Mn spins switch at Hc^-, which is larger than that of the ZFC Hc. While, during the field increasing state from –0.5 T to 0.5 T, spin of the Mn and Ru ions at the interfaces will rotate towards the field increasing direction, which is favoured by the antiferromagnetic coupling. The Mn spins switch at Hc^+, which is smaller by an H_EB compared to that of the ZFC Hc. Hence, a negative exchange bias is expected. Similarly, after cooling the superlattice with +ve Hcool > Hcool^s to lowest temperature, delta becomes< 90°. During the hysteresis loop measurement on decreasing the field from 0.5 T to – 0.5 T, spin of the Mn and Ru ions at the interfaces will rotate towards the decreasing field direction, which is favoured by the antiferromagnetic coupling. The Mn spins switch at Hc^-, which is smaller by an H_EB compared to that of the ZFC Hc. While, during the field increasing state from –0.5 T to 0.5 T, spin of the Mn and Ru ions at the interfaces will rotate towards increasing field direction, which is opposed by the antiferromagnetic exchange coupling. The Mn spins switch at Hc^+, which is larger than that of the ZFC Hc. Thus, a positive exchange bias is expected. The H_EB is proportional to the exchange coupling energy, which is expressed as E_(Ru,Mn)=- J/A ∑(S_Ru ) ⃗ ∙ *(S_Mn ) ⃗ . So, when, H_EB=0, the coupling energy is zero for the Hcool= Hcool^s. Since J is non zero, (S_Ru ) ⃗ * (S_Mn ) ⃗ is zero, which is possible if the angle between the spin of Mn and Ru ions is 90°, while the Ru-O-Mn bond angle remains 180° [4]. The linear variation of H_EB vs M^(-1) for Hcool=0.1 T provides the E_(Ru,Mn)≅ - 0.87 erg/ (cm)^2. In contrast, the change of H_EB with M^(-1) for the H_cool=5 T shows rectilinear behaviour with two slopes.The superlattices with n ≤8 show E_(Ru,Mn) ≅ - 1.25 erg/(cm)^2, while the superlattices with n ≥8 exhibits E_(Ru,Mn) ≅1.52 erg/(cm)^2 [4]. The interfacial coupling energy of most of the FM/AFM systems is <1 erg/(cm)^2 [3]. For Hcool=0.1 T, the AFM coupling energy is 8 times larger than the AFM coupling energy (0.11 erg/(cm)^2) [4] of the LSMO/SRO bilayer, while it is close to that of the value observed in the system like FeF_2/Fe and Fe_3O_4/CoO [2]. Interestingly, the AFM coupling energy strongly depends on the Hcool and at Hcool=5 T, it is significantly larger than the most of the FM/AFM systems [4]. This along with observed larger Hc (~3T) and sharp drop in magnetization below TN support the presence of strong AFM coupling at the interfaces of tetragonal SRO- PMO superlattices. The results demonstrate that the SRO- PMO superlattice could be a model system for the investigation of the interfacial exchange coupling in functional oxides. References: 1. A. Hirohata and K.Takanashi, J. Phys. D: Appl. Phys. 47, 193001(2014). 2. J. Nogues and I. K. Schuller, J. Magn. Magn. Mater. 192, 203 (1999). 3. P. Padhan and W. Prellier, Phys. Rev. B 76, 024427 (2007). 4. A. Sahoo, P. Padhan and W. Prellier, ACS Appl. Mater. Interfaces. 9, 36423-36430, (2017).

Resume : GaFeO have started to gain attention due to their appealing properties [1-2]. Compounds with a composition around GaFeO3 are piezoelectric with an additional large linear magnetoelectric effect. Oxides close to the Ga2FeO4 composition have been proposed for hyperthermia treatments and as the insulating paramagnetic layer in magnetic tunnel junctions. Therefore, there exists a scientific and technological interest on the development of GaFeO thin films. To accomplish this objective, we have firstly monitored the structural and magnetic properties of Fe70Ga30 thin films during thermal treatments in oxygen atmosphere in a temperature range from 500 °C to 800 °C [3]. We have observed that the oxidative annealing promotes the formation of Ga-rich aggregates as indicated by XAFS. At 600 °C, we have found evidences of Ga oxidation whereas Fe maintains its metallic state. Ga starts to evaporate from the layer surface at 700 °C leaving a Ga-poor layer that is eventually oxidized into ?-Fe2O3. Further increase of the temperature up to 800 °C only produces the decomposition of the layer. As oxidation during annealing seems not an adequate route to produce GaFeO, we have investigated the possibility of using electrodeposition. We have analyzed the influence of the electrolyte composition, pH, and overpotential on the structural and magnetic properties of thin films. [1] S. H. Oh et al, Appl. Phys. Lett. 106 (2015) 142902. [2] J. Atanelov and P. Mohn, Phys. Rev. B 92 (2015) 104408. [3] P. Alvarez-Alvarez, A. Prados, A. Muñoz-Noval, R. Ranchal, J. Alloys Compnd. 713 (2017) 229.

Resume : Ferroelectric polarization related charge conduction has shown intriguing properties of ferroelectric heterostructure devices, such as ferroelectric tunnel junction, switchable diode and ferroelectric memristor. Recently, ferroelectric polarization has been proposed for synapse device exhibiting a high on/off ratio, low power consumption and short process time. In ferroelectric-based synapse devices, gradual electroresistive modulation is associated with change of ferroelectric domain configuration, providing the controllability of the electric conductance for the effective operation of synapse devices. The conductance can be finely tuned by voltage pulses and set to evolve according to a synaptic learning rule called spike-timing-dependent plasticity (STDP). In this work, we demonstrated a ferroelectric-field-effect transistor based ferroelectric heterojunction synapse devices with channel layer of metal to semiconducting transition (MST) oxide. Ferroelectric polarization switching and ferroelectric tunneling can modulate the amount of applied energy to MST oxide phase transition and channel conductance at the same time. Our structure with analog-like electroresistive modulation is highly desirable for realizing efficient synapse device. This research was supported by the MOTIE (Ministry of Trade, Industry & Energy (#10080643) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device. *Author for correspongding author : tjchoi@sejong.ac.kr

Resume : Resistive switching or resistive random access memory (Re-RAM) devices are the most promising candidates for the future non-volatile memory devices because of their high switching speed, high endurance, and low power consumption [1-4]. The structure of Re-RAM devices is metal/insulator/metal (MIM), which is very simple and their memory characteristics depend upon the top electrode, bottom electrode and the insulating layer of the device. Since transition metal oxides and semiconductor oxides are the ubiquitous insulating materials with unique characteristics, therefore many researchers focus their attention on these materials to use their thin films (TFs) as insulating material in MIM structure. In this study, the tri-layer dielectric/insulating medium memory devices with structure Pt/Ti/TiO2/HfO2 /TiO2/Pt were prepared for non-volatile memory applications. The total thickness of tri-layer insulating oxide layers was ~ 60 nm keeping 20 nm thickness for each thin film. The TiO2 thin film was deposited on Pt bottom electrode by magnetron sputtering. Then HfO2 thin film was deposited on the TiO2 thin film by magnetron sputtering again. Again by using magnetron sputtering another thin film of TiO2 is deposited over HfO2 thin film. Thus 20 nm HfO2 thin film is sandwiched between two 20 nm TiO2 thin films. The thickness of Pt bottom electrode was ~ 30 nm and that of Ti top electrode was ~ 50 nm. A capping layer of Pt with thickness ~ 30 nm was deposited at the top electrode. Pt and Ti were deposited using thermal evaporation and sputtering, respectively. The tri-layer Re-Ram device Pt/Ti/TiO2/HfO2 /TiO2/Pt exhibited bipolar resistive switching. The SET voltages were at ?+1.3 V and RESET voltages were at ~ -1.2 V. The device exhibited good endurance characteristics with the ON/OFF ratio of ~500. The retention tests confirmed the non-volatile characteristics of the memory device. The conduction mechanism of ohmic conduction, space charge limited conduction (SCLC) and Schottky conduction have been investigated for the conduction and switching mechanisms. References: [1]. Waser, R.; Aono, M. Nanoionics-Based Resistive Switching Memories. Nat. Mater. 2007, 6, 833?840. [2]Chang T.-C, Chang K.-C, Tsai T.-M, Chu T.-J, Sze S. M. Resistance random access memory. J. Mattod, 2015, 19: 254-264 [3] Lin C Y, Wu C Y, Wu C Y, et al. Effect of top electrode material on resistive switching properties of ZrO2 film memory devices. IEEE Electron Device Lett, 2007, 28: 366?368 [4] Choi B J, Jeong D S, Kim S K, et al. Resistive switching mechanism of TiO2 thin films grown by atomic-layer deposition. J Appl Phys, 2005, 98: 033715

Resume : Obtaining a cost-effective production of YBa2Cu3O7-coated conductors (CCs) with high performance by chemical solution deposition (CSD) has attracted tremendous interest for large scale power applications. Control of structural evolution and thin-film physical properties becomes limited to variations in precursor solution chemistry and heat treatment conditions. Here we present the influence of fast heating ramps (~ 50 times faster than conventional ones) for CCs fabrication. We have conducted a systematic study on the intermediate phase evolution, growth kinetics and microstructural defect evolution, based on which we find that flash heating (FH) growth process offers several advantages compared to traditional thermal processes. Epitaxial YBCO films can be obtained in a wider growth temperature window starting at lower temperature (750-810 ºC) making this process suitable for multilayer growth avoiding reactivity between layers and being compatible with the continuous reel-to-reel industrial production. Fast heating ramps are also beneficial to prepare YBCO nanocomposites with higher control of nanoparticle distribution in the superconducting matrix. Importantly, we find that the FH growth process promotes the formation of high concentration of structural defects and thus nanostrain, key parameters for improving the vortex pinning properties. Therefore, the FH growth process provides huge opportunities for promoting high throughput reel-to-reel production of CCs.

Resume : Thin-film transistors (TFTs) using oxide semiconductor channels have intensively been investigated as oxide semiconductors such as In–Ga–Zn–O (IGZO) show field effect electron mobilities in excess of 10 cm2 V−1 s−1, higher than that of hydrogenated amorphous silicon. Additionally, such oxide semiconductors can be deposited by a wide range of large-area compatible vacuum-based techniques. Despite however the tremendous potential, further advancements have been hampered by a lack of hole-transporting oxides with similar or comparable transport characteristics to their n-type counterparts, limiting the applications of oxide-semiconductor-based TFTs to relatively simple devices and circuits such as backplanes for active-matrix information displays where n-channel TFTs only are needed. Although there are a reports on p-type doping of traditional n-type oxides, the subject still remains controversial as doping of metal oxides is typically one-sided due to self-compensation so alternative metal oxides that show intrinsic p-type characteristics are required. To date, only a few compounds such as SnOx and Cu2O have been realised and incorporated into p-type TFTs. Both compounds however show relatively low hole field-effect mobilities in the range between 0.001 and 4 cm2 V-1 s-1 and the TFTs show significantly high off currents. Collectively, these results reaffirm that field-effect mobility of >1 cm2 V-1 s-1 is generally achievable with Cu2O transistors. In the case of Cu2O this is further supported by the fact that Hall Effect measurements showed mobilities exceeding 100 cm2 V-1 s-1 reaching values as high as 250 cm2 V-1 s-1. This presentation reports on the deposition of both p-type Cu2O-based as well as n-type ZnO-based thin films by spray coating in air at substrates temperatures in the range between 100 oC and 450 oC from acidic and alkaline solutions of Cu2O and ZnO nanoparticles. The films’ properties were investigated by means of UV–Vis spectroscopy, x-ray diffraction, AFM and field-effect measurements and the effects of the solution’s pH and the substrate’s temperature are discussed in respect to the thin films’ structure and electronic transport properties. Furthermore, TFT’s employing spray coated cubic Y2O3 gate dielectrics and Cu2O and ZnO-based semiconducting channels show excellent operating characteristics, in particular low operation voltage, high charge carrier mobility on the order of 4 cm2 V-1 s-1, low off currents (1 nA) and high current modulation ratio >10^4. The deposition methodology as well as the results that are presented here, demonstrate an alternative route for the manufacturing of large-area oxide electronics and represents a significant step towards the development of low-cost, large-area complementary metal-oxide-semiconductor circuits at moderate temperatures.

Resume : Nowadays, nanostructured composites materials have been actively investigated due to their unique physical properties caused by interface and size effects [1]. Particularly, synthesis and studying of superparamagnetic magnetite (Fe3O4) nanoparticles are of great scientific interest in recent years. This is mainly due to their various practical applications in the field of technology and medicine. On the other hand, such materials as superionic conductors in conjunction with highly dispersed oxides exhibit unusual ion-transport properties. A conductivity enhancement by 1-3 orders of magnitude, with room temperature conductivity value ~ 10-3 S•cm-1, can be achieved in the Ag+ ion conducting two-phase composite systems simply by dispersing submicron size particles of such oxides as A12O3, SiO2, ZrO2 or SnO2, known as second-phase dispersoid, into a moderately ion-conducting first-phase host-matrix salts like AgI, AgCl or AgBr [2]. Furthermore, it was shown that the temperature of the superionic phase transition could be lowered down by tens of degrees by reducing the size of ion-conducting particles [3]. But not only the properties of host ion-conducting matrix changes, due to an active interfacial interaction the properties of second-phase may also change significantly. Therefore, we have developed a special two-step solution phase technique for fabrication of magnetite/silver iodide nanocomposites. Obtained nanocomposites were characterized using scanning electron microscopy, X-Ray powder diffraction and X-Ray photoelectron spectroscopy. Silver iodide forms predominantly cubic γ-phase on the magnetite surface while it average grain size amounts to 21-23 nm. It was also revealed that silver iodide is chemically bonded to the magnetite surface. The values of saturation magnetization (Ms) for all composites are high enough to allow managing them by applying magnetic field. Particularly, for composites with x < 0.3 the value of Ms is greater than 55 emu/g. [1] Ajayan PM, Schadler LS, Braun PV (2006) Nanocomposite science and technology. Weinheim, Wiley [2] Agrawal RC, Gupta RK (1999) Superionic solids: composite electrolyte phase – an overview. J Mater Sci 34:1131-1162 [3] Makiura R, Yonemura T, Yamada T, Yamauchi M, Ikeda R, Kitagawa H, et al (2009) Size-controlled stabilization of the superionic phase to room temperature in polymer-coated AgI nanoparticles. Nature Materials 8:476-480

Resume : We prepared multiferroic composite thin films consisting of ferrimagnetic spinels MFe2O4 (e.g. M = Co, Ni) and ferroelectric BaTiO3 by spin-coating of solutions containing the respective metal cations in the solvent mixture N,N-dimethylformamide/acetic acid. The chemical solution deposition was followed by decomposition and crystallization steps. A single coating leads to a film thickness of roughly 30 nm. To obtain the desired thickness, the coating process was repeated several times. The ferrite- and BaTiO3-components were arranged in a bilayer structure. Two different substrates were used, namely platinum coated silicon wafers and SrTiO3 single crystals. For the films on Pt-coated silicon a highly oriented columnar growth of the ferrite phase was found, while the films on SrTiO3 show a nearly epitaxial growth. Phase formation of the oxides was monitored by XRD and Raman spectroscopy. To investigate the crystallographic orientation additional rocking curves and pole figure X-ray measurements were carried out. SEM and AFM images show homogenous and smooth surfaces. Magnetic and polarization hysteresis loops prove the coexistence of ferrimagnetism and ferroelectricity. In addition we observed strong magnetic anisotropies of the in-plane and out-of-plane magnetizations.

Resume : Human activities such as industry or agriculture are the potential issues of water and soil pollution. Heavy metals and organic molecules are the most hazardous pollutants. Nowadays, the existent solutions are not answering to the whole problem: expensive equipment, non-respectful of the new contaminants standards into biological environment and inefficient for industrial discharges, sewage and sludge depollution. A new process must be designed using functional materials and ensuring an efficient and selective removal of micropolluants in different media. The specifications of such materials are: to be synthesized in a large scale and cost-effective process, to be non-toxic and applicable without risks in water-soils, easily magnetically manipulated, highly selective for the pollutant chelation and fully recyclable. In this project, magnetic supports are made of iron oxide clusters coated by a mesoporous silica. On one hand, the core is a hollow sphere with high magnetic properties which allow an easy and selective separation of the composite using a magnetic process. On the other hand, the mesoporous silica shell is protecting the magnetic core and is functionalized with chelating agents which target metal or organic pollutants. One important issue is the recycling: desorption of contaminants from the solid support can be made by changing physicochemical conditions or even by magnetic hyperthermia of a solution containing nanocomposites to induce the release of pollutant.

Resume : Magnetoelectric (ME) composites, which consist of ferroelectric and magnetic phases are potential candidates for multifunctional device applications. In our study, we report the ME properties of BaTi0.92Sn0.08O3-NiFe2O4 particulate composite, where BaTi0.92Sn0.08O3 acts as the piezoelectric phase and NiFe2O4 acts as the magnetostrictive phase. BaTi0.92Sn0.08O3 is a lead free piezoelectric which shows a high piezocoefficient of 296 pC/N and remanent polarization value of 6.92 μC/cm2, whereas NiFe2O4 exhibits a substantial magnetostriction coefficient value. BaTi0.92Sn0.08O3 and NiFe2O4 have been synthesized using solid state reaction and sol-gel route, respectively. The (1-x)(BaTi0.92Sn0.08O3)-xNiFe2O4 [x=0.1-0.4] particulate composites were then synthesized by mixing of the calcined individual ferroic phases using solid state reaction method. ME voltage coefficient (αME = dE/dH) of the composites was measured as a function of applied d.c. magnetic field at different frequencies. The resultant ferroelectric, magnetic and magnetoelectric properties of these synthesized composites will be presented in this conference. Keywords : magnetoelectric, composites, piezoelectric

Resume : Solar water oxidation has drawn great attention as a promising technology for the green and sustainable production of various chemicals. In principle, they can be electrochemically produced using water as an electron donor. However, a slow water oxidation kinetics at most electrode/electrolyte interfaces has hindered its practical application. To address such a problem, we recently developed a simple method to prepare highly efficient water-oxidation photoanode (PA) by modifying the surface of PA with catalytic multilayers (CM). For example, the deposition of CM composed of inactive cationic polyelectrolytes and anionic polyoxometalate catalysts by layer-by-layer assembly provided a significantly improved photocatalytic activity to any kind of underlying PA. The underlying mechanism for the observed performance improvement was kinetically studied using a nanoporous BiVO4 with and without CM by electrochemical impedance spectroscopy. The deposition of CM significantly suppressed the recombination of photogenerated charge carriers and improved catalytic transfer of charge carriers at the electrode/electrolyte interface. As a result, PAs modified by CMs exhibited much higher performance than those prepared by conventional methods. We believe that the present study can provide insights to design and fabrication of novel electrochemical and photoelectrochemical devices.

Resume : Production of solar fuels using photoelectrochemical (PEC) cells has drawn great attention as a sustainable energy and environmental technology. Typical PEC cells are composed of an n- and p-type semiconductors as a photo-anode and -cathode, respectively. Due to their inherent problems, however, it is critically required to modify their surface with various functional materials to enable efficient and stable overall water splitting without external bias. Conventionally, they have been modified by using materials-specific modification methods under complex and harsh processing conditions. In the present study, we developed an efficient and stable PEC cell using a Cu2O photocathode and BiVO4 photoanode only with simple solution processes under mild conditions. Briefly, they were modified with catalytic multilayers (CM) of cationic polyelectrolytes and anionic polyoxometalate electrocatalysts for hydrogen (HER) or oxygen evolution reactions (OER) by layer-by-layer assembly. After the modification with CM, they exhibited not only a significantly improved catalytic activity but also enhanced stability. As a result, we could readily fabricate a bias-free PEC cell for overall water splitting. Considering our approach is simple and universally applicable, it can provide insight to design and fabrication of novel PEC devices.

Resume : TiO2 has been considered as one of the most promising support materials for catalysts due to its abundance, high stability, and strong interaction with metal species. Although the low conductivity of TiO2 poses challenges for its application in electrocatalysis, nanostructuring of TiO2, doping of other elements into TiO2, and inducing oxygen deficiency in the TiO2 lattice can be possible pathways to solve this problem. For example, oxygen deficient TiO2 has been used as support material for electrocatalytic applications, especially for the oxygen reduction reaction. Even though there is a possibility of severe changes in the structural and electrochemical properties of oxygen deficient TiO2 in the presence of saturated oxygen, a systematical study is still pending. Here, we prepared an oxygen deficient TiO2 nanowire film on a conducting glass electrode to investigate its structural changes as well as its electrochemical properties. Rutile TiO2 film was firstly grown using a hydrothermal method, and then transformed via various annealing treatments to oxygen deficient TiO2 which has higher conductivity. Using this as support material, metal catalysts were deposited after the reduction of metal salt. A systematic study of crystal structure, oxidation state, and chemical bonding nature was done using advanced TEM technologies. Details and prospects on the investigation of the structural and electrochemical change of the support before and after oxygen-containing electrocatalytic reactions will be discussed.

Resume : In the field of environmental remediation strategies, multifunctional materials able to act for pollutants adsorption and degradation at the same time are highly desirable. In this framework, post-synthesis treatments represent a powerful tool for the modulation of the chemico-physical and functional properties of nanocomposite materials. In this study, Bi12O17Cl2/(BiO)2CO3 nanocomposite materials were studied as bifunctional systems for depuration of wastewater and synthesized at room temperature and ambient pressure by means of controlled hydrolysis of BiCl3, in presence of a surfactant (Brij 76). Cold treatments with UV-light or thermal annealing at different temperatures (370 – 500 °C) and atmospheres (air, Ar/30 % O2) of the pristine samples were adopted in order to modulate the Bi12O17Cl2/(BiO)2CO3 relative amounts and hence morphology, surface areas, ζ-potential, optical absorption in the visible range and the adsorption/degradation of Rhodamine B (RhB) and Methyl Orange (MO), used as model pollutants. The best performance was achieved by (BiO)2CO3-rich samples which adsorbed 80 % of MO and decomposed the remaining 20 % by visible light photocatalysis. Irrespective of the dye, all the samples were able to almost complete the adsorption step within 10 minutes contact time. Bi12O17Cl2-rich composite materials displayed a lower adsorption ability, but thanks to the stronger absorption in the visible they behaved as more effective photocatalysts. The obtained results evidenced the ability of the employed strategy to modulate sample properties in a wide range thus pointing out the effectiveness of this approach for the synthesis of multifunctional inorganic materials for environmental remediation.

Resume : BaTiO3-based ferroelectric ceramics show interesting properties such as high dielectric constant, low losses, and high hydrostatic piezoelectric coefficient. For these reasons, barium titanate is widely used in the electronic industry for manufacturing miniaturized multilayer ceramic capacitors, underwater transducers and self-regulating thermistors. BaZrxTi1-xO3 (BZT) solid solutions with perovskite structure show a series of phase transitions and a progressive evolution of ferroelectric order, from long-range order typical of classic ferroelectrics (x = 0-0.15), via a diffuse transition behavior (x = 0.15-0.25), to short-range order typical of relaxors (x ≥ 0.25) and finally paraelectric non polar state for neat BaZrO3. The trivalent europium ion (Eu3+) is well known for its bright luminescence in the red spectral region. Even very small variations in the coordination sphere of Eu3+ ions induce major changes in their emission spectrum. Thanks to these features, Eu3+ is a unique and powerful local structural probe. In this framework, we have investigated the photoluminescence (PL) emission of dense BZT ceramics doped with Eu3+ at the Ba site, with composition EuyBa1-yZrxTi1-x-y/4O3 (y = 0.01, x = 0, 0.05, 0.15, 0.30, 0.50, 0.70, 1), in the temperature range -100 to 140°C. The dielectric permittivity of the samples was measured from -150 to 150 °C at 102-106 Hz to determine reference values of the phase transition temperatures and the type of polar order. The PL spectra underwent to significant shape and intensity variations as function of both composition and temperatures, which can be correlated with the nature (long-range or short-range) of polar order. The observed behavior can be rationalized considering the off-center displacement of Eu3+ ions with respect to the lattice position occupied by barium. The strong variation of the PL spectra induced by temperature change can be exploited to develop ratiometric self-calibrating luminescence thermometers working from room temperature down to liquid nitrogen.

Resume : Amorphous molybdenum sulfide (a-MoSx) is a promising hydrogen evolution catalyst owing to its low cost and high activity. A simple electrodeposition method (cyclic voltammetry) allows uniform formation of a-MoSx films on conductive surfaces. However, only few attempts have been directed to the application to the photoelectrodes as a co-catalyst, and so far researches suffer from the lack of in-depth understanding of a-MoSx electrodeposition in terms of photoelectrochemical properties. Herein, we demonstrate the morphology of a-MoSx, deposited on a TiO2/Sb2Se3 photocathode could be modulated by varying the starting potential. The cathodically initiated a-MoSx showed conformal film-like morphology, while anodic initiation induced inhomogeneous particulate deposition. The film-like morphology of a-MoSx was subjected to catalyst activation, which improved the photocurrent density and reduced the charge transfer resistance at the semiconductor/electrolyte interface as compared to its particulate counterpart. X-ray photoelectron spectroscopy confirmed that different chemical states of a-MoSx (photoelectrochemically active sites) were developed based on the electrodeposited a-MoSx morphology. The research provides an effective approach for uniformly depositing cost-effective a-MoSx on nanostructured photoelectrodes, for photoelectrochemical water splitting.

Resume : Graphene is the most studied 2D material. However there are many others that can be prepared by exfoliation from crystals. All of them show a strong potential in the development of novel functional materials. A textured growth of perovskite oxides has been recently obtained by pulsed laser deposition on arbitrary substrates with 2D inorganic nanosheets layers.[1] This opens the door to the fabrication of high-performance microelectronic devices with tailored properties. However epitaxial films are difficult to prepare by solution methods. Nanosheets could be an appropriate tool to induce preferred orientation in solution derived films. Additionally, the seeding effect of the nanosheets can accelerate the nucleation of the oxide, resulting in a significant reduction of the crystallization temperature of the film. This would facilitate the direct integration of these films in the emergent flexible electronics, where traditionally perovskite oxides are excluded because of their high processing temperatures.[2] This work studies the fabrication of solution derived ferroelectric PbZrxTi1-xO3 (PZT) films on Pt-coated silicon substrates with a seed layer of Ca2Nb3O10 (CNO) nanosheets. Suspensions of the CNO nanosheets are Langmuir−Blodgett deposited on the substrate for the further spin-coating deposition and crystallization below 500 ºC of the PZT film. The crystal structure and properties of the resulting materials are discussed. [1] Nijland et al., Adv.Funct.Mater., 2015, 25, 5140. {2} Bretos et al., Chem. Soc. Rev., 2018, DOI: 10.1039/c6cs00917d. Supportted by the Spanish Project MAT2016-76851-R

Resume : High-k dielectrics have extensively been studied as alternatives to SiO2 as gate dielectrics for the next generation of field-effect transistors employing metal-oxide semiconducting channels. Among these, ZrO2 is the most extensively studied dielectric and is widely considered to be excellent an candidate because of their relatively high dielectric constant, good thermal stability, and large band gap. The use however of substrate temperatures compatible with flexible glass i.e. up to 500 oC results in ZrO2 dielectrics of a monoclinic structure limiting its dielectric constant to 15. The desired high-temperature (>800 oC) ZrO2 with a tetragonal cubic phase can readily be stabilized, at lower temperatures by the use of different dopant elements (or compounds such as CaO, MgO, Y2O3). Because of its high dielectric constant (in excess of 24), yttria-stabilized zirconia (YSZ) has thus been suggested as a promising gate dielectric candidate. Here, we report on the deposition and characterisation of yttria-stabilised zirconia (YSZ) gate dielectrics grown by spray coating in air at moderate temperatures of about 450 oC from zirconium acetylacetonate in methanol. Y2O3 doping was achieved by blending the zirconium host precursor with Y2O3 nanoparticles (average diameter of 20 nm) dispersed in HCl solution. The YSZ films of various Y2O3 content were investigated by means of UV-Vis absorption spectroscopy, x-ray diffraction, AFM, admittance spectroscopy, spectroscopic ellipsometry, and field-effect measurements. Analyses of the YSZ films reveal smooth films (RRMS< 1 nm) of a tetragonal (fluorite) phase with dielectric constant in the range between 17 and 26. In2O3-based TFT transistors employing YSZ deposited at an optimal Y2O3 content of about 4 % mole, reveal excellent operation characteristics in terms of low voltage operation, low leakage currents (1 nA/cm2), high electron mobility in excess of 35 cm2/Vs and high on/off current modulation ration in the order of 10^7. These performance enhancements may be attributable to the large band offsets and small lattice mismatch between the YSZ dielectric and In2O3.

Resume : IGZO thin-film transistors (TFTs) has been used for commercialized display panel because they have enough high mobilities, suitable for large area displays and lower processing temperatures. RF sputtering is employed to deposit amorphous oxide semiconductor with large-area and uniformity. In this work, we fabricated IGZNO target by ball-milling of each oxide powder including nitride, which can be more stable for uniformity and easy to confirm the effect of nitrogen incorporation in IGZO TFTs. We directly deposited IGZNO films from IGZNO target and fabricated thin-film transistors also compared the device performances with devices fabricated through a conventional sputtering procedure with nitrogen gas flow. We found that nitrogen in IGZO target affected the charge carrier concentration correlated with oxygen vacancies to enhance electrical characteristics of TFTs. X-ray photoelectron spectroscopy and Ultraviolet Photoelectron Spectroscopy TEM, FT-IR and UV-Visible spectroscopy were carried out for analyzing the films. We expect that IGZNO target could fabricate high performance metal oxide TFTs in large area with stable process and uniformity of characteristics.

Resume : Whilst progress on solution-processed oxide semiconductors has been rapidly advancing, research efforts towards the development of dielectric materials has been relatively slow, with most of the reported work performed using dielectrics based on SiO2 that results in high voltage transistor operation and hence increased power consumption. Gate dielectric materials with high dielectric constants are desirable, but the band offset condition that requires a reasonably large band gap should also be satisfied. The latter is of particular concern when wide band gap (>3 eV) metal oxide semiconducting channels are being employed as the number of suitable candidate gate dielectric materials to be used will be significantly reduced. The obvious solution to both the low dielectric constant and narrow band gap issues could be the use of a composite dielectric material with combined high permittivity, wide band gap and low leakage current. Additionally, despite their extraordinary performance, vacuum-based deposition techniques still suffer from high manufacturing costs and limited large-area deposition capabilities. To overcome this issue, significant research has been focused on the development of alternative deposition processes based on solutions. Based on the above, here we report on the structural, optical, electronic and dielectric properties of a number of dielectric composites based on the combination of a high-k/low band gap dielectric such as Nb2O5, TiO2 and La2O3 with a low-k/wide band gap such as Al2O3. The Al2O3.TiO2, Al2O3.Nb2O5 and LaAlO3 composite gate dielectrics were grown from soluble precursors by spray coating in air at moderate temperatures (400 oC) varying the Al/Ti, Al/Nb and Al/La atomic ratios. Each compound was investigated by a wide range of characterisation techniques including UV−vis absorption spectroscopy, spectroscopic ellipsometry, atomic force microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and impedance spectroscopy. The above-mentioned gate dielectrics were further implemented in thin film transistors employing spray coated ZnO semiconducting channels. Analyses reveal dielectric compounds that for optimised stoichiometries show very smooth (RRMS< 2nm) amorphous films with excellent dielectric properties i.e. high dielectric constants of about 15 combined with wide band gaps of 6 eV, low leakage currents in the order of 5 nA/cm2 and excellent environmental stability. The related thin film transistors employing these gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics which are hysteresis-free, have tunable operation voltage (5-10 V), high on/off current modulation ratios of >10^6, and electron mobility of about 12 cm2 V-1 s-1.

Resume : A wide range of rare earth metal oxides (REOs) constitute promising candidates for high-k gate dielectrics, as they combine excellent dielectric properties, i.e., high dielectric constant and low leakage currents with wide bandgaps, in the range between 3.9 and 6 eV. Yet, another attractive feature of rare earth oxides that further boosted their research is the excellent stability and interface properties with silicon. Also, their relatively close lattice constant match to silicon further enhances the possibility of epitaxial growth. Epitaxial growth of REOs (i.e., Gd2O3) on GaAs has been reported, and further investigations demonstrated their potential applications in a number of III–V-based optoelectronic devices. Due to their wide bandgaps (>3 eV) however, metal oxide based semiconductors require gate dielectrics with a relatively wide in order to inhibit conduction by the Schottky emission of electrons or holes into the oxide bands. A number of wide bandgap REOs (La2O3, Y2O3, Nd2O3) have shown promise for implementation in TFTs employing metal oxide semiconducting channels. Among those, Gadolinium oxide (Gd2O3) is the least investigated one and a small number of works have been reported. In this report we demonstrate the spray coating deposition of Gd2O3 thin films at moderate temperatures (≈400 °C) over large area, by using custom made Gadolinium tris(2-salicylaldiminoethanol) precursor. The films were deposited by spray coating at moderate substrate temperatures (440 oC) in air and characterised by UV-Vis, FT-IR, impedance spectroscopy, AFM, XRD and field-effect measurements. Data analysis revealed Gd2O3 films of cubic structure, wide band gap of about 5.5 eV and dielectric constant in the range between 9 and 13. TFTs employing Gd2O3 dielectrics and In2O3 semiconducting channels show low leakage currents (<1 nA/cm2), low subthreshold swing, high on/off current modulation ratio (>10^7) and electron mobilities in excess of 70 cm2 V−1 s−1.

Resume : Using a water-treatment process, we have successfully fabricated intrinsic Josephson junction (IJJ) tunneling devices in Bi2Sr2CaCu2Oy (Bi-2212) high-temperature superconductor. To fabricate IJJ tunneling devices, it is necessary to flow an electrical current along c-axis direction which IJJ’s structures natively arrange. For an attainment of current pathway along c-axis direction, a surface of Bi-2212 single crystal was partially contacted with purified-water at room temperature for 0.5 - 10 h. By this treatment, an electrical property of the Bi-2212 single crystal between electrodes was deteriorated. Therefore, a current pathway was changed from ab-plane direction to c-axis direction. Actually, the annealed Bi-2212 single crystal showed clear voltage jumps, so call “Josephson junction property”, in current-voltage characteristics.

Resume : In order to study the nanosize effect in BiFeO3 (BFO)/(Fe,Zn)3O4 (FZO) nanostructures, a set of samples have been grown by pulsed laser deposition on SrTiO3:Nb(001) substrate using a single target composition of (Bi1.1FeO3)0.65(Fe2.2Zn0.8O4)0.35. Oxygen pressure and deposition temperature have been respectively settle to approximately 0.9 Pa and 588 °C for all the samples. Deposition time for the set of samples are 1, 2 and 3 hours with a growth rate of 0.6 nm/min. The insulating/ferroelectric properties of BFO and the semi-conducting/non-piezoelectric properties of FZO make Conductive-Atomic Force Microscopy (C-AFM) and Piezoresponse Force Microscopy (PFM) good candidates to study the nanoscale electrical properties of such kind of nanostructures. C-AFM reveals generally that BFO usually grow as small islands surrounded by FZO for all the samples. Out of Plane and In Plane PFM images also confirm this tendency: piezoelectric response arise from the small BFO islands whereas no signal is recorded from FZO. The lowest thickness sample show similar behavior but reveals more a grain by grain growth with small BFO islands. PFM loops have been performed by in-field and off-field methods on all the samples. Whereas all samples show an imprint effect, no PFM off-field loop could be recorded on the thinnest sample. By using PFM and C-AFM, we were able to fully investigate the size effect in BFO/FZO nanostructures.

Resume : For decades, corrosion has been a ubiquitous concern in most industrial applications. It costs the oil & gas industry billions of US dollars per year. Therefore, it is of great significance to take effective protective measures for corrosion control. Sweet corrosion, which is caused by contact with carbon dioxide in water, is the main type of corrosion in oil & gas pipelines and still occurs despite the presence of corrosion inhibitors. Siderite (FeCO3), the main product of sweet corrosion, forms a scale that can insulate the iron from solution and therefore may be exploited for corrosion prevention. In our previous work, the surfaces of siderite scale were identified, allowing for the opportunity to explore the interaction of corrosion inhibitors on scale stability in the present work. The binding sites of inhibitors on the FeCO3 surface are studied with hybrid Density Functional Theory (DFT). The most effective distribution of inhibitors on siderite scale surface will be defined by the end of the work. This not only reduces financial costs, but is also beneficial to the environment since some inhibitors and their production process are toxic.

Resume : Epitaxial thin films of ordered double-perovskite La2CoMnO6 (LCMO) have recently attracted a great deal of attention for possible applications in spintronic devices. Due to its ferromagnetic and insulating character, LCMO is a good candidate for active insulating barriers in spin filters [1]. Both saturation magnetization and Curie temperature (Tc) are very sensitive to cationic ordering and are substantially reduced in disordered samples [2]. In this work, high quality epitaxial LCMO thin films were grown on (001) SrTiO3 substrates by a simple and cost effective polymer assisted deposition (PAD) method. In the PAD process, the different metal salt precursors are dissolved in an aqueous Polyethylenimine (PEI) polymer solution. The amount of metal cations bound to the polymer and the solution viscosity are directly related to the amount of PEI used. The desired stoichiometry ratio can be easily controlled by mixing different metal-polymer precursor solutions with corresponding metal molar ratios. The precursor solution was spin coated on (001)-STO substrates and the resultant coatings were thermally annealed in flowing oxygen. Our epitaxial films show saturation magnetization values of about 6 µB/f.u. and a Tc=230K, thus indicating full cationic ordering of Co2 /Mn4 in a double perovskite structure. The performance of the LCMO films as spin filter barrier is under investigation. [1] L. López-Mir et al., Scientific Reports, in press [2] R. Galceran et al., Appl. Phys. Lett. 105, 242401, 2014 *We acknowledge support from Severo Ochoa Program Grant SEV-2015-0496, Coachsupenergy (MAT2014-51778-C2-1-R) and Chinese Scholarship Council (CSC)

Resume : Structural transformation of Ge-rich HfO2 films, produced by RF magnetron co-sputtering, is studied versus power density applied on Ge target and annealing temperature (T) using spectroscopic ellipsometry, Raman scattering, FTIR and XRD methods. As-deposited undoped HfO2 films were found to be polycrystalline. Both monoclinic and tetragonal phases were detected. The doping of the films with Ge reduces the degree of film crystallinity towards amorphous structure. This latter was found to be stable for T<600°C. Annealing at higher T causes a phase separation process. The segregation of Ge and HfO2 phases occurred via the formation of Ge nanoclusters and tetragonal HfO2 phase. This latter formed at T=600-670°C, while the Ge nanoclusters crystallized at T=700-800°C. For T>800°C the transformation of tetragonal HfO2 phase to monoclinic one was observed. This effect was explained by the formation of volatile GeO and decrease of Ge content in the films. Obtained results support theoretical prediction of the impact of Ge doping on the stability of tetragonal “high-k” HfO2 phase in Ge-rich films.

Resume : Tungsten, molybdenum oxides and metal tungstates are widely used in catalysis, photocatalysis, gas sensing, as well as in electrochromic applications. In our research we prepared hexagonal (h-) WO3, MoO3, Bi2WO6 and FeWO4 hydrothermally and investigated the effects of different reaction conditions (temperature, reaction time, additives) on the composition and morphology of the products. In addition, we examined and compared the photocatalytic activity of the products. For the first time we managed to prepare FeWO4 nanosheets, with a thickness of 20-30 nm and a length and width of 0.5-10 µm. We synthetized hexagonal and ortorhombic MoO3 in the form of wires and rods and Bi2WO6 particles in the nanometer range. Both FeWO4 nanosheets and h-WO3 nanorods had good photocatalytic activity. We also tested the photocatalytic activity of MoO3 and Bi2WO6.

Resume : TiO2 -WO3 nanocomposites were prepared using electrospinning and annealing, and their features and applications were studied in detail. The aim of the study was to fine tune the properties of nanocomposites by using different proportions of TiO2and WO3 precursors. For the nanofiber synthesis, polyvinylpyrrolidone, tetrabutyl titanate and ammonium metatungstate were dissolved in a mixture of water, acetic acid and ethyl alcohol. The nanofibers formed after electrospinning were calcined by heating at a rate of 5 ∘ / min until 500 - 600 ∘ C to remove the polymer component. The TiO2 -WO3nanocomposites were characterized using TG / DTA-MS, XRD, SEM-EDX, TEM, FTIR, and Raman. The as-synthesized nanomaterials were studied for their application in photocatalysis and fuel cell electrodes.

Resume : Conventional solar cells have limited energy conversion efficiencies because photons with energy lower than the band gap are not absorbed by the system and those with higher energies are inducing phonons. A possible way to improve the efficiency of solar cells consists in using multi-junctions with several layers, covering the largest range of the solar spectrum. In this way Mott Insulators have been proposed as solar-absorbers because their property of carrier multiplication could be efficient [1]. LaVO3 is among those which could be interesting, with an indirect forbidden band gap of 1.1 eV and a good absorption coefficient [2] which seems optimal according to the Shockley-Queisser limit [3]. Usually crystallized lanthanum vanadates films are deposited by ALD, MBE or obtained with powder reactions. After studying the conditions of lanthanum-vanadium-oxygen magnetron co-sputtering (metallic and poisoned regimes) we propose a two-step method to obtain LaVO3 thin films. Thin films with different La/V atomic ratios are first sputter deposited. The La/V ratio is evaluated by a SEM. Secondly to get crystallized LaVO3 we use an external annealing in a reducing atmosphere composed of a mix of Ar and H2 then films are analyzed by XRD and XPS. References [1] E. Manousakis, Physical Review B 82 (2010). [2] E. Assmann, & al., Physical Review Letters 110, 078701 (2013). [3] W. Shockley & al., Journal of Applied Physics 32, 510 (1961).

Resume : Cu-Fe-O thin films were co-sputtered from metallic Cu and Fe targets in the presence of a reactive argon and oxygen gas mixture. Evolution of the coatings composition as a function of the discharge current dissipated on each target allowed to obtain convenient composition. The influence of annealing temperature under vacuum and air atmosphere on physico-chemical properties of the films was investigated. The films deposited at ambient temperature were initially amorphous and need to be annealed at different temperatures in the range of 653-1023 K under vacuum and air atmosphere to achieve delafossite structure. CuFe2O4 and CuO as the secondary phases were clearly detected by XRD analysis, and could evidently affect the CuFeO2 films optoelectronic properties. Relatively, rising the annealing on vacuum was better to obtain CuFeO2 delafossite phase and improved their optoelectronic properties. The optimum conductivity and transparency were achieved for the film annealed in air at about 723 K with a maximum visible transmittance up to 83%. Their direct band gap energy of about 2.1 eV is measured. The film possesses the optimum properties after annealing under vacuum at 653 K; its average transmittance in the visible region can reach 35% while the film’ s conductivity is about 0.1 S cm−1.

Resume : Despite the materials performances being superior to those of organic materials, inorganic materials are typically excluded for use in flexible and deformable electronic systems because of their rigid nature and the requirement for high processing temperature. This work presents a novel method of utilizing rigid NiZn-ferrite films in a flexible platform and offers an opportunity to realize a flexible wireless power transfer (WPT) module. Inkjet printing was introduced in this study since it can coat NiZn-ferrite films as well as pattern inductor coils for WPTs. A thermochemically inert buffer layer was selected based on a thermodynamic analysis and was introduced as a buffer layer for the NiZn-ferrite to prevent chemical reaction between the ferrite film and the substrate and ensure that the ferrite film can be easily separated from the substrate during a high-temperature sintering process. A Ag-inductor coil was printed on the NiZn-ferrite layer, and then the entire layer was embedded into polydimethylsiloxane, which renders the WPT module flexible. The flexibility of the WPT module was characterized by a bending test, and the structural and magnetic properties were also investigated. The performance of the flexible WPT module was demonstrated by transmitting wireless power to a light emitting diode.

Resume : The demand for wearable electrics is increasing due to their capability of facile interaction of electronic devices with human body. Wearable sensors for data input to wearable electronics which can be easily mounted on clothing or attached onto the body are required. In particular, multi-functional stretchable touch/force sensors for wearable touch panel are of great interest for combination of touch/force sensors with stretchable data output device. Here we report sensitive, stretchable projected capacitive (p-cap) type touch/force sensor device where the touch and force can be detected simultaneously but distinguished. The p-cap touch/force sensor requires two electrodes to generate an electromagnetic field. Top electrode is for sensing touch/force signal, and bottom electrode is for reading the signal. We used piezoresistive materials of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and EMIM-TCB for top electrode to separate touch and force stimulation. For bottom electrode, a conductive electrode was used. The optical and electrical properties of electrode materials were tested by static and dynamic stretching. The electrical sensing characteristics of this sensor were also analyzed before and after stretching. The electrical performances of the multi-functional stretchable touch/force sensors will be discussed in detail.

Resume : Superparamagnetic iron oxide nanoparticle (SION) has spurred a great interesting due to peculiar magnetic properties and potential applications in medical image enhancement and drug delivery. The current problems in those SIONs, which are hindering for practical medical applications, are non-uniformity size distribution, particle agglomeration, non-crystallinity, and low magnetic property. In this paper, magnetic nanocrystals with different size and morphology were prepared by solvothermal method in N-hexane-surfactant system with the precursors of Fe(acac)3 and iron powder. The structural properties of SION were characterized by X-ray diffraction，Raman spectrum and High Resolution Transmission Electron Microscopy (HRTEM). XRD confirmed the grown SION nanoparticle with good crystalline. HRTEM images showed the particle size of SION is about 5.6 to 6.8 nm, non-agglomeration and with uniform distribution. HRTEM found that the morphology and nanocrystals of SION has initially changed from the irregular crystal to triangles and quadrilaterals shape, and finally to the hexagonal nanoparticles, with the increasing reaction time. The Magnetic measurement measured by Superconductor Quantum Interference Device (SQUID) showed that the as-prepared samples were superparamagnetic, and the maximum saturation magnetization was 62.65 emu/g, which is reported among the largest magnetic property of SION at a size of 6.3 nm. The grown mechanism of SION and related magnetic properties are also theoretically explained and discussed. Key words: Fe3O4 nanocrystal, Solvothermal method, Morphology, Magnetic property.

Resume : The bio-application of nano magnetic particle requires small particle size, high stability and high magnetic property. While small magnetic grain size is to size–match with small bio-molecular, higher magnetic property is required by a large signal output. The conventional superparamagnetic magnetic particle, Fe3O4, for example, is very challenge to satisfy the demand for small particle size, high stability and higher magnetic property simultaneously. In this paper, a CoFe2O4 nanoparticles system were synthesized in the hexane-water-surfactants system (A method or sample A) and the ethanol-surfactants system (B method or sample B) respectively. Based on the characterization of X-ray diffraction, it is found that the all the samples synthesized by A and B method were grown with very good crystalline. Transmission Electron microscopy (TEM) verified that the particle size synthesized by both A and B method are at the range of 2-5 nanometer. The characterization of magnetic property is measured by Superconductor Quantum Interference Device (SQID). The saturation magnetizations (Ms) of sample prepared by A and B are 60.95 emu/g and 61.20 emu/g respectively, suggesting Ms at same value level. The coercivities (Hc) were 1860.90 Oe for sample A and 423.32 Oe respectively, indicating a very large Hc difference. After post-heat treatment, Ms, Mr, Hc, and remanence ratio R of all samples were not changed significantly. Finally, the growth mechanism and the effects on the crystal size and magnetic properties of these samples in difference reaction systems were discussed. Key words: CoFe2O4 nanocrystal, Chemical wet method, Reaction system, Grain size, Magnetic property.

Resume : Using readily available renewable resources i.e. solar energy and seawater to secure sustainable fuel and freshwater for humanity is an impactful quest. Here, we have designed solar thermal collector nanocomposites with Ag that possess efficient photothermic properties for highly targeted interfacial phase transition reactions that are synergistically favorable for both catalysis and vaporization reactions. The photothermic effect arises from plasmonic metal nanoparticles exhibits localized interfacial heating which directly triggers surface-dominated catalysis and steam generation processes, with minimal heat losses, reduce thermal masses and optics implementation. The solar thermal collector nanocomposites are seawater and photo stable for practical solar conversion of seawater to simultaneously produce clean energy and water. Finally, a proof-of-concept all-in-one compact solar hydrogen and distillate production prototype demonstrates the viability of sustainable photothermic driven catalysis and desalination of seawater under natural sunlight. Meanwhile, the photothermal pyroelectricity and piezoelectricity capabilities are also demonstrated. A proof-of-concept for concurrent photothermal management and enhanced solar pyroelectric generation under a real outdoor environment is also validated.

Resume : Doped semiconductor nanocrystals are an emerging class of materials hosting localized surface plasmon resonance (LSPR) over a wide wavelength range (from Vis to IR). Studies so far have focused on tuning LSPR wavelength by controlling the dopant and carrier concentrations in diverse semiconductor species. However, the influence of intrinsic crystal structure and particle shape on LSPR remain poorly explored. We illustrate how these structural factors collaborate to perform novel LSPR characteristics that are unprecedented in metal systems. For instance, in hexagonal cesium-doped tungsten oxide nanocrystals, the dominant influence of crystalline anisotropy causes strong LSPR band-splitting into two distinct peaks with comparable intensities [1]. Modeling, typically used to rationalize particle shape effects, was refined by taking into account the anisotropic dielectric function due to crystalline anisotropy, thus fully accounting for the aspect ratio-dependent evolution of multiband LSPR spectra [1]. This finding highlights the limitations of conventional treatments of LSPR that assume isotropic dielectric constants and attribute multimodal peaks uniquely to shape anisotropy effects. It also extends our insight to exquisitely tune LSPR lineshape and near-field enhancement via synthetic control of shape and crystalline anisotropies of semiconductor nanocrystals. [1] J Kim*, A Agrawal, F Krieg, A Bergerud, D J Milliron*, Nano Lett. 16, 3879-3884 (2016)

Resume : We demonstrate novel inverted light-emitting devices based on tungsten trioxide (WO3) nanostructures. Two different types of WO3 nanostructures, including nanocluster layer (NCL) and nanorod arrays (NAs), were grown on the indium-tin oxide (ITO) substrates by the hydrothermal method. The prepared WO3 nanostructures own high transmittance in the visible range and band gaps of 3.5?3.75 eV. From the electrical measurement, 300 nm-height WO3 NAs possess the highest conductivity among all the WO3 nanostructures. An ultra-thin polyethylenimine ethoxylated (PEIE) layer was deposited on top of WO3 nanostructures as the buffer layer to improve device performance. Inverted devices with the configuration of ITO/WO3 NCL or NAs/PEIE/poly(2-methoxy-5-(2?-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/ WO3 film/Au were constructed and evaluated. The reduced photoluminescence decay time of MEH-PPV on WO3 layer is observed due to more carrier dissociation on WO3/MEH-PPV interface, while increased fluorescence lifetime obtained by inserting PEIE suggests enhanced radiative recombination of excitons. The best device based on WO3 NAs with height of 300 nm showed a max brightness of 3,079 cd/m2 and current efficiency of 0.22 cd/A. This is the first demonstration of inverted light-emitting devices using WO3 NAs as the ETL. Our results demonstrate that WO3 nanostructures can be promising alternatives for the fabrication of hybrid light-emitting devices.

Resume : We demonstrate inverted perovskite light-emitting devices (PeLEDs) based on zinc oxide nanorod arrays (ZnO NAs) as the electron transport layer (ETL) and methylammonium lead bromide nanoplatelets (MAPbBr3 NPLs) as the emissive material for the first time. ZnO NAs were first grown vertically on the ITO substrate via the hydrothermal method. A thin layer of polyethyleneimine ethoxylated (PEIE) was deposited on top of the ZnO NAs to reduce energy barrier and improve electron injection efficiency. The utilization of PEIE modified the conduction and valence bands of ZnO NAs, which favored electron injection into the active layer. Moreover, different weight ratios of poly(N-vinylcarbazole) (PVK) were blended with MAPbBr3 NPLs to make evenly dispersed nanocomposite films, thereby enhancing the device performance. It is seen that the photoluminescence of MAPbBr3 NPLs:PVK nanocomposite film was increased due to reduced self-quenching and prolonged carrier lifetime. Inverted PeLEDs with the configuration of ITO/PEIE-modified ZnO NAs/MAPbBr3 NPLs:PVK/TFB/Au were fabricated and evaluated, using TFB as the hole transport layer and Au electrode as the anode. The current density of the devices containing PVK matrix was significantly suppressed compared to those without PVK. Herein, the best device revealed a max brightness of 495 cd/m2 and a low turn-on voltage of 3.1 V that shows potential use in light-emitting applications. To the best of our knowledge, this is the first report on PeLEDs comprising MAPbBr3 NPLs as the emissive material and ZnO NAs as the ETL.

Resume : An important economic improvement of white light emitting diode (LED) is based on the use of lanthanide-free phosphors that are supposed to convert UV light into visible one, thanks to down-conversion (DS) process. ZnO nanoparticles have aroused an increasing interest since they possess a variety of intrinsic defects that provide light emission in the visible range without the introduction of any additional impurity. Our recent patented industry-capable (in terms of legislation concerns) and cost effective chemical solution approach (PCT WO 2016/038317 A1) led to mesospheric self-assembly hybrid ZnO-PAA nanomaterials (PAA = polyacrylic acid) that can be used as original nanostructured material which revealed to be efficient scatterer, resulting in a significant increase of the light-harvesting capability and emission performance. Herein, we will address the use of such self-assembly nanostructured ZnO materials as luminophor for LED devices. We will demonstrate how and why optimizations of (i) the set-up of the synthesis (reaction and washing steps), (ii) the molecular weight of the commercial polymers PAAH and PAANa (1800-250000) and the ratio of their mixture, (iii) cationic doping and (iv) core-shell structure lead to remarkable efficiency of white emission light of DS thin films in LED technology.

Resume : Deep-ultraviolet (DUV) photodetector and sensor technologies operating in the UV-C spectral region (< 280 nm) are an emerging field of research because of the potential applications in various domains, such as high-temperature flame detection, missile-launching detection, environmental monitoring, binary switching in imaging techniques, remote control, chemical analysis, ozone layer monitoring, secure space-to-space communications, and biological threat detection. Production of conventional photodetectors operating in the UV region involves high-cost fabrication methods. Moreover, as the operational range of most advanced UV photodetectors is restricted to the UV-A and UV-B region. Producing a cost-effective and reproducible flexible DUV (UV-C) photodetector with high responsivity, operating at ambient conditions for large-scale applications remains a challenge. In this work, for the first time, we present the solution-processed metal-oxide quantum dots (QDs) for photo-detection in the UV-C region (224 nm) while remaining solar blind, operating at ambient conditions. The QDs were synthesized by environmental friendly method (ultrafast laser ablation), which allows using a flexible substrate. Such device exhibits immunity to stress while providing extremely stable and repeatable responses in the bending tests. Our device exhibits high responsivity (294 mA/W) in the UV-C range and is characterized by ultrafast response speed, stable switching performance, and high stability. We have achieved the highest responsivity for QDs-based DUV photodetectors. Overall, our work offers the possibility for commercially producing highly stable and cost-effective large-scale flexible optoelectronic devices.

Resume : Ni based nanostructures are attractive catalytic materials for many electrochemical applications among which non-enzymatic sensing, charge storage, water splitting. In this work, we clarify the synthesis kinetics of Ni(OH)2/NiOOH nanowalls grown by chemical bath deposition at room temperature and at 50 °C. The optimized nanostructures is then applied to non-enzymatic glucose sensing reaching the utmost sensitivity of 31 mA/(cm2mM). Using scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and Rutherford backscattering spectrometry (RBS) we found that the growth occurs through two regimes: first, a quick random growth leading to disordered sheets of Ni oxy-hydroxide, followed by a slower growth of well-aligned sheets of Ni hydroxide. High growth temperature (50 °C), leading mainly to well-aligned sheets, offers superior electrochemical properties in terms of charge storage, charge carrier transport and catalytic action, as confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. These results on the optimization and application of low-cost synthesis of this Ni based nanostructures have a large potential for application in catalysis, (bio)sensing, supercapacitors areas.

Resume : Metal oxide nanoparticles have many applications in fields like fillers, optical materials, catalysts or sensor applications. Synthetic approaches are dominated by batch processing, applying wet chemical routes such as the sol-gel process or forced hydrolysis in autoclaves. These methods have the disadvantage that reproducibility is often limited from batch to batch and yields are usually low. Continuous processing methods are dominated by high temperature processing, such as spray pyrolysis or high temperature combustions, which have the disadvantages that the resulting particles are often agglomerated. In this report we reveal a wet chemical method that is based on a microjet mixing, which allows the synthesis of large quantities of various nanoparticles even on a laboratory scale. In addition this method has the advantage that under specific conditions in the reactor exclusively crystalline particles are obtained. Beside typical metal oxides of Zn, Fe, Ti and Sn also SiO2 and RSiO1.5 particles can be obtained with this method in high yields. Another advantage of this method is that the final product is a suspension of the nanoparticles which can be directly used for the production of devices, which was proven in the development of metal oxide based sensor systems.

Resume : The development of high performance glucose sensors has attracted particular attention because of increasing needs in analysis tools for medical diagnostics over the past decade. Due to its low cost and outstanding catalytic ability, copper oxide modified electrodes are widely studied for non-enzymatic glucose sensor. Among these modified electrodes, the oxides mostly synthesized by solution method are transferred onto a glassy carbon electrode (GCE) to serve as an electrode of a sensing device. However, a self-supporting electrode with functional oxide nanostructures has rarely been studied. A self-supporting electrode can collect the charges generated from the reaction directly and avoid the contact resistance between GCE and the deposited oxides. Such a self-supporting electrode with oxide nanostructure shall be able to enhance the performance of sensing devices. In this study, we successfully demonstrate a self-supporting electrode composed of high surface area nanostructure by using a novel potential cycling method. The Cu/CuxO nanoflower structure was obtained by applying a potential cycling method to grow copper oxide on the surface of Cu nanowires. The Cu/CuxO nanoflower structure was identified to be a pure Cu core wrapped with a layer of Cu2O and follow by the CuO outer layer according to TEM analysis. The nanoflowers provide a large electrochemically active surface area for efficient catalysis of glucose. The heterojuction between multilayer structure makes it highly efficient to collect the charges generated from the surface of CuO where the glucose oxidation reaction takes place to the electrode itself. The influence of Cu nanowires length and different nanostructures grown under the electrolytes of various pH values using a potential cycling method on the sensing performance will be investigated. The modified Cu/CuxO nanowire array electrode shows a high sensitivity (up to ~1900 ?A/mM^(-1) *cm^(-2)), wide linear range (up to ~10 mM) and fast response time (within 1 s).