Nanoparticles in dielectric matrix: from synthesis to device applications for photonics, electronics, and bio sensing

Resume : Silicon nanocrystals represent a powerful class of nanostructures which is opening new substantial opportunities for photonics and photovoltaics. In nanocrystals quantum confinement and interface effects play a major role in the final opto-electronic response. Moreover the opportunity of doping the nanostructures has been considered to further tune their transport and/or optical properties. In this talk I will present the outcomes of several ab-initio calculations in the framework of Density Functional Theory and Many-Body Perturbation Theory for free and matrix embedded Si nanocrystals. In particular the effect of dopant impurities on the electronic, optical, and transport properties of Si-nanocrystals embedded in a SiO2 matrix or passivated by H or OH groups will be discussed . By systematically changing the position of the dopants we have been able to discriminate its favoured localization, and its effect on the nanocrystal response. In addition, we considered the case of co-doped nanocrystals revealing a complete new scenario for the stable positions. Finally we will show how the interaction between different Si nanocrystals is a promising route to foster the establishment of third generation photovoltaics due to carrier multiplication effects

Resume : Recent experimental works have shown that Si nanocrystals co-doped with P (donor) and B (acceptor) impurities exhibit very interesting optical properties [1]. Efficient photoluminescence (PL) is reported in a wide energy range (0.85-1.8 eV) that overcomes the bulk Si bandgap limitation. The nanocrystals are very stable and are therefore very promising for applications. Here I present electronic structure calculations for Si nanocrystals doped with the same number of donor and acceptors. The variation of the excitonic gap versus nanocrystal size and impurity concentration is studied in a systematic manner. The experimental trends are correctly reproduced and explained. I analyze the intrinsic effects of disorder on the linewidth of the PL spectra. The influence of the impurities on the PL lifetime is also discussed. [1] H. Sugimoto et al, J. Phys. Chem. C 117, 11850 (2013).

Resume : Silicon nanocrystals (Si-NCs) embedded in dielectric matrices have been extensively studied due to potential applications in novel opto-or nanoelectronic devices. For the latter case, a detailed understanding of the electrical doping of Si-NCs is required. Theoretical and experimental studies have shown the possibility to dope Si-NCs with boron (B) or phosphorus (P). Moreover, it was shown that heavily doped Si-NCs can exhibit localized surface plasmon resonance (LSPR). In this work, we investigate P-doped Si-NCs embedded in SiO2 films. The Si-rich SiO2 films were obtained by co-evaporation of SiO and SiO2 using e-beam and the P doping was achieved by using a GaP decomposition source. The structural and optical properties were studied by Fourier transform infrared absorption spectroscopy (FTIR), scanning transmission electron microscopy (STEM) and photoluminescence (PL) spectroscopy. The Si-NCs related PL intensity depends on the P concentration. For low doped films, we still observe PL in the near infrared originating from radiative recombination of charge carriers confined in Si-NCs. For heavily doped films, the PL intensity quenches due to the Auger effect. Meanwhile, a strong absorption is observed in the infrared which is attributed to LSPR. STEM studies reveal that the LSPR may originate from epitaxial P-doped Si-NCs growing out at the interface between the Si substrate and the films. Heavily P-doped SiOx films may be of potential interest for future infrared sensors.

Resume : Carrier multiplication in phosphor and boron co-doped silicon nanocrystals has been investigated at room temperature, in a broad excitation energy range up to 4 times of optical bandgap. Results obtained from the photoluminescence quantum yield measurements and induced absorption spectroscopy have been compared. Using both techniques we conclude that the carrier multiplication process does take place in these co-doped nanocrystals. The experimentally measured excitation energy dependence is found similar to the space-separated-quantum cutting responsible for this process in undoped Si nanocrystals in SiO2. The microscopic model for the carrier multiplication, making use of both nanocrystalline core and dopant states is presented. We also observe that dopants induce strong bleaching of the free carrier absorption at the emission energy. The new implications of this finding on the model of the radiative recombination in co-doped Si nanocrystals are discussed.

Resume : Thanks to their bulk semimetal nature mercury chalcogenides compounds (HgTe and HgSe) are well suited for the design of mid and far infrared optical properties. In addition to an inverted band structure and quantum confinement, HgS(e) have been demonstrated to be self doped, which leads to the air stable observation of an intraband absorption signal. We report about the synthesis of HgSe nanocrystals with tunable intraband peak from 3 to 25µm. Because this intraband signal brings new concepts for the engineering of optical properties of IR colloidal quantum dots (CQD), we investigate the origin and tunability of the doping. We demonstrate that doping is due to a reduction by the environment resulting from the large work function of the material combined with its narrow band gap nature. We also show that surface capping ligands can be used to tune the doping level over 1 order of magnitude. Finally, we use on chip tunnel spectroscopy as a way to evidence that doping is already existing at the single particle scale.

Resume : The nanometer-scale light-matter interactions between fluorescent emitters and plasmonic metal nanoparticles have immense implications for device physics and super-resolution imaging. Coupling to the enhanced field and increased local density of states about these excited nanoantennas leads to brighter molecules by enhancing the rates of both excitation and decay. Most investigations of this plasmon-couple fluorescence are performed on the bulk scale, where heterogeneities mask the fundamental relationships between dye and nanoparticle, or with electron microscopy based techniques, which do not directly probe the way a nanoantenna modifies the emission of a dipole emitter. Here, we instead use single-molecule fluorescence microscopy, a flexible, general technology for ultrahigh-resolution, real-time optical imaging, to directly probe fluorescence emission near a single plasmonic particle without ensemble averaging. By beating the diffraction limit that restricts traditional light microscopy with minimal perturbations, this imaging approach has had high impact across the disciplines because it enables high-sensitivity measurements, eliminates heterogeneity in characterization, resolves positions on the nanometer scale, and characterizes motions and features in situ. I will discuss how we have realized, characterized, controlled and understood plasmon-enhanced fluorescence based on observations of single fluorescent molecules coupled to single gold nanoparticles.

Resume : The coupling between collective electron oscillations (surface plasmons) with charge transport has led to an emerging field called “plasmo-electronics” which has been exploited for enhancing the performance of various optoelectronic devices and could provide a new class of light responsive materials. In particular, coupling of light and charge via localized surface plasmons have led to the discovery that plasmonic excitations can influence macroscopic flows of charge and, conversely, that charging effects can influence the plasmonic excitation. In this context, we used convective self assembly (CSA) to create arrays of self-assembled molecules/metal nanoparticle stripes on glass substrate. By tailoring size and nature material of the nanoparticles (e.g. Au, Ag…), as well as the ligand molecule (e.g. dodecanethiol, tris(2,4-dimethyl-5-sulfonatophenyl)phosphine…) we were able to point out both normal and inverse photo-conductance. We have investigated the photo-conductance generation in NP assembly under focused laser illumination as a function of illumination wavelength and intensity, applied voltage, temperature. A model of thermal conduction combined with trap state filling dynamics in a nano-composite medium allows us to interpret the plasmon-induced photoconductance in these NP arrays.

Resume : Organized nanoscale structures that can guide or manipulate the propagation of electromagnetic fields at optical frequencies are of great importance for applications in sensing, all-optical computing and photovoltaics. Periodic plasmonic nanoparticle arrays can support narrow surface lattice resonances (SLRs) due to coupling between localized surface plasmons and diffractive modes. However, simple and low-cost fabrication methods suitable for large scale applications that create structures with intense electromagnetic fields with dynamic tunability are yet to be developed. Here, we address a method suitable for fabricating large area devices that support fully reversible, dynamic actuation of SLR modes. We use wet-chemically synthesized core-shell nanoparticles[1] for dynamic assembly at the air-water interface into hexagonally ordered, cm2- sized, plasmonic arrays[2]. For obtaining stable and refractive index sensitive SLRs, a crosslinked PNIPAM top coating was applied. Hence the refractive index surrounding the monolayer can be tuned dynamically by swelling and deswelling the coating by switching between temperatures below and above its volume phase transition temperature. This behavior lead to a device with a dynamically tunable and fully reversible SLR. [1] T. Honold, K. Volk, A. Rauh, J.P.S. Fitzgerald, M. Karg, J. Mater. Chem. C, 2015, 3, 11449-11457 [2] K. Volk, J.P.S. Fitzgerald, M. Retsch, M. Karg, Adv. Mater., 2015, 27, 7332.

Resume : Optical sensors have emerged as an attractive platform for hydrogen detection in the recent years because they provide means for remote readout and are considered safer than electrical sensors as they pose no risk of spark generation. An interesting avenue within the field is the use of nanostructured metal-hydride systems as signal transducer in nanoplasmonic hydrogen sensors [1]. In particular, we have previously demonstrated hydrogen sensors based on PdAu alloy nanoparticles, which exhibit hysteresis-free hydrogen detection over a wide pressure range and whose accuracy, sensitivity, and response time [2,3] exceed the performance targets set by the automotive industry [4]. To further tailor these sensors for application in realistic environments, however, strategies must be implemented to improve their stability against “poisons” such as CO and SOx, as well as H2O, and to reduce cross-sensitivity. Here, in analogy to our previous work on thin films [5], we utilize a thin (ca. 30 nm) sputtered polytetrafluoroethylene (PTFE) coating on Pd and PdAu alloy nanoparticles. As the main result, we find the PTFE coating on the nanoparticles to significantly improve both their hydrogen sorption and desorption kinetics, leading to sub-second sensor response time even at room temperature for the PdAu alloy nanoparticle system. Furthermore, we also discuss the obtained improved resistance towards poisoning gases. References (1) Boon-Brett, L.; Bousek, J.; Black, G.; Moretto, P.; Castello, P.; Hübert, T.; Banach, U. Identifying Performance Gaps in Hydrogen Safety Sensor Technology for Automotive and Stationary Applications. Int. J. Hydrogen Energy 2010, 35, 373–384. (2) Wadell, C.; Syrenova, S.; Langhammer, C. Plasmonic Hydrogen Sensing with Nanostructured Metal Hydrides. ACS Nano 2014, 8, 11925–11940. (3) Wadell, C.; Nugroho, F. A. A.; Lidström, E.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Hysteresis-Free Nanoplasmonic Pd-Au Alloy Hydrogen Sensors. Nano Lett. 2015, 15, 3563–3570. (4) Nugroho, F. A. A.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Bottom-Up Nanofabrication of Supported Noble Metal Alloy Nanoparticle Arrays for Plasmonics. ACS Nano 2016, 10, 2871–2879. (5) Ngene, P.; Westerwaal, R. J.; Sachdeva, S.; Haije, W.; de Smet, L. C. P. M.; Dam, B. Polymer-Induced Surface Modifications of Pd-based Thin Films Leading to Improved Kinetics in Hydrogen Sensing and Energy Storage Applications. Angewandte Chemie International Edition 2014, 53, 12081-12085.

Resume : In recent years, DNA origami has emerged as a potential platform for developing new organometallic complexes with targeted properties. The electro-magnetic response of such DNA constructs can be precisely controlled by careful and strategic placement of nobel metal nanoparticles onto the origami structures. To aid in this design effort, we apply generalized Mie theory to investigate the surface plasmon response of nanoparticles envisioned in recent synthetic efforts. This exercise provides useful design criteria for developing new functional materials.

Resume : Directed assembly of nanoparticles is a promising alternative for original nanoparticle organizations. New kinds of optical properties are expected when semi-conductive or metallic nanoparticles are concerned. Using liquid crystal matrices oriented by their interfaces, we create ordered arrays of topological defects [1] that act as traps for nanoparticles, allowing for an anisotropic directed assembly. For trapped fluorescent nanorods, a fine control of the polarization of the single photons is obtained [2]. Similarly the orientation of gold nanorods leads to the control of their luminescence as well as of their plasmon resonance by light polarization . I will show that, when the nanoparticle concentration is increased, single chains are formed, and can lead to a strong electromagnetic coupling between the particles [3]. We are not only capable of linearly confining the particles, but also of varying the inter-particle interactions and thus modify their optical properties which are sensitive to the inter-particle distance [4]. The chains being oriented by the defects, the electromagnetic coupling becomes controlled by light polarization [3, 4]. For fluorescent nanorods we show that the coupling can even increase the nanorod degree of polarization. [1] D. Coursault, Soft Matter 12 (2016) 629. [2] L. Pelliser et al, Adv. Funct. Mat. 25 (2015) 1719. [3] D. Coursault et al., Adv. Mat. 24 (2012) 1461. [4] D. Coursault et al., ACSNano 9 (2015) 11678

Resume : From catalysis to sensing, metal nanoparticles are the most commonly used and produced nanomaterials. There are basically two steps for formation of metal nanoparticles, as depicted in commonly utilized wet chemistry procedures: 1) Reduction of the metal ion, 2) stabilization of the formed nanoparticles e.g. against formation of larger agglomerates. For both steps, the preparation methods involve using of some hazardous chemicals. Especially in the latter step, these chemicals retain in the sample and hinder the function of the nanoparticle (catalytic activity etc.). In this presentation, we show a method to by-pass these commonly used hazardous chemicals and to form the nanoparticles in-situ by mechanical input. Once they are formed the nanoparticles are surrounded and stabilized by the polymer chains – also leaving out the widely used stabilizing agents. We display the similarities and differences in nanoparticle formation in different polymer media from elastomers, to thermoplastics and biopolymers, e.g. cellulose, and to commercial sticky tapes1, comparing the results obtained by SEM and TEM imaging, XRD analysis, and X-ray photoelectron spectroscopy (XPS). In the heart of the mechanochemical formation of metal nanoparticle-polymer composites lies the production of mechanoradicals,2 which can be produced via various mechanical input (room temperature mechanical squeezing to cryomill), and can be monitored by UV-Vis Spectroscopy, electron spin resonance spectroscopy (ESR), and FTIR-ATR spectroscopy. We finally verify the versatility of the mechanochemical method by showing the mechanochemical formation of the ‘nanoalloy’ composites and ‘triple nanocomposites’; namely cellulose-metal nanoparticle-synthetic polymer composites. 1) H. T. Baytekin, B. Baytekin, S. Huda, Z. Yavuz, B. A. Grzybowski, Mechanochemical activation and patterning of an adhesive surface toward nanoparticle deposition. J. Am. Chem. Soc. 137, 1726–1729 (2015). 2) H. T. Baytekin, B. Baytekin, B. A. Grzybowski, Mechanoradicals created in “polymeric sponges” drive reactions in aqueous media, Angew. Chem. Int. Ed 51, 3596-3600 (2012).

Resume : Plasmonic nanoparticles embedded into a dielectric matrix create an optical medium which allows electromagnetic fields to be enhanced and manipulated. The optical properties of such medium can be tailored by chemical composition (doping) of the metal nanoparticles which modifies their unit cell structure. The latter can be determined by geometric phase analysis of a high resolution TEM image through mapping of the deformation components relative to the reference undistorted lattice. However, a reference lattice might not present in the image since nanocrystals can be buried in an amorphous or crystalline matrix whose unit cell is different or disoriented with respect to that of the nanocrystal. Here, we propose a new method which allows the absolute values of the interplanar distances and angles within a crystalline nanoparticle to be extracted without a need for a reference lattice in the same image. For this, the distortions of a nanocrystal image induced by projecting lenses and the CCD camera are measured then subtracted by using an image in which the two-dimensional unit cell describing the projected structure of the crystal is known a priori. We illustrate the power of the method using two examples including Ag nanocrystals formed by low-energy ion implantation in a thick SiO2 layer and hexagonal AsSb nanocrystals formed after annealing within delta-Sb doped GaAs layer grown at low-temperature by molecular beam epitaxy.

Resume : The interest for nanostructured functional materials has led to the search for new and versatile fabrication methodologies, among which nanochemistry and self-assembly have become promising routes. The metamaterials are artificial composites presenting unusual properties of light propagation. The search for meta-properties, which could open the way to technical breakthrough in optics such as hyperlenses and cloaking, has been mostly focused on nanoplasmonic systems. We propose a bottom-up fabrication technique for uniaxial anisotropic plasmonic metamaterials, using self-assembled block copolymers hybridized with gold nanoparticles. In particular, we study periodic lamellar stacks of alternating layers of pure polymer and layers of composite of polymer loaded with a high density of gold nanoparticles. The spectral variation of their anisotropic effective dielectric permittivity is determined by spectroscopic ellipsometry using appropriate effective medium models. For large gold loading, the lamellar stack presents a frequency domain, in which the ordinary and extraordinary components of the dielectric function are of opposite signs. This peculiar property, called ?hyperbolic?, allows for the propagation of large magnitude wavevectors, carrying details finer than half the wavelength, otherwise corresponding to evanescent non-propagative waves in a usual dielectric. We therefore demonstrate the use of self-assembly for the fabrication of bulk hyperbolic metamaterial.

Resume : Colloidal quantum dots (QDs) are semiconductors nanocrystals with size-dependent optoelectronic properties. Their size tuneable emission in the visible spectral range makes these nanocrystals very interesting for (commercial) applications like light emitting diodes (LEDs), bio-imaging, and flat screen televisions. Coating QDs with silica has proven to be a successful manner to increase the stability of QDs. Moreover, silica coated QDs are water dispersible and can be easily functionalized, which is beneficial regarding biomedical applications. The reversed micro emulsion method is often used to coat hydrophobic QDs with silica, resulting in monodisperse 20-80 nm silica spheres with one QD per particle. However, main disadvantage of this method is a significant decrease in QD emission intensity (up to 60%) during the silica coating, resulting in less bright QDs. Using (time resolved) emission spectroscopy, we investigated the influence of the different reactants used during the silica coating on the optical properties of CdSe/CdS/ZnS core/shell QDs. We found that the base catalyst used has a major impact on the emission intensity of the resulting particles. Significantly brighter silica coated QDs can be obtained when ammonia is replaced as a base catalyst by small, water-soluble organic bases. Using small amines as base catalyst monodisperse silica-QD nanoparticles with a photoluminescence quantum yield (PLQY) of 30% are obtained starting from core/shell QDs with a PLQY of 40%.

Resume : Germanium QDs embedded in Si3N4 and SiO2 matrices in Multilayer structures with SiO2 barriers have been grown using PECVD method on Silicon and Quartz substrates. As-grown characterization is done using ellipsometric spectroscopy. Rutherford Back Scattering (RBS) is used for compositional analysis. Post annealing is done using both conventional furnace and rapid thermal annealing (RTA) methods from 600 C to 1000 C for crystallisation. Size and concentration of Ge QDs are controlled using thickness of multilayer structures. The thickness (and Size of QDs) varied between 1 nm to 15 nm. Structural and Optical studies are used using RAMAN , HRTEM and PL spectroscopy. Crystallisation process is studied using Raman spectroscopy and HRTEM and effect of matrix on crystallization is discussed. Threshold for crystallization is observed to be at lower temperature for samples annealed at Si3N4 matrix. Raman analysis is done taking in to account Phonon confinement effect and stress exerted by matrix. Raman spectra shows different stress for samples grown on Si3N4 and SiO2 matrices. HRTEM graphs show good crystallisation and control over QD size and also QD-QD space in growing direction. Lateral growth for thicker samples also is observed. Photoluminescence study is done using 325 nm of HeCd laser at room temperature. Samples show strong visible PL at 2.3 eV and 3.1 eV which is stronger for smaller QDs. The origin of size dependent PL is discussed for different classes of samples.

Resume : Semiconductor nanocrystals (NCs) experience stress and charge transfer by embedding materials or ligands and impurity atoms. In return, the environment of NCs experiences a NC stress response which may lead to matrix deformation and propagated strain. Up to now, there is no universal gauge to evaluate the stress impact on zinc blende (zb) and diamond lattice NCs and their response as a function of NC size. I deduced geometrical number series as analytical tools to obtain the number of NC atoms, bonds between such NC atoms and interface bonds of such NCs for seven high symmetry zb and diamond lattice NCs with low-index faceting: {001} cubes, {111} octahedra, {110} dodecahedra, {001}-{111} pyramids, {111} tetrahedra, {111}-{001} quatrodecahedra and {001}-{111} quadrodecahedra [1,2]. These fundamental insights into NC structures allow for major advancements in data interpretation and understanding of zb- and diamond-lattice based nanomaterials [3-7]. The analytical number series can serve as a standard procedure for stress evaluation in solid state spectroscopy due to their deterministic nature, easy use and general applicability over a wide range of spectroscopy methods as well as NC sizes, forms and materials. [1] D. König, AIP Adv. 6, 085306 (2016) {open access} [2] https://youtu.be/v8Ni_LlbdZQ [3] D. König, D. Hiller, S. Gutsch, M. Zacharias, Adv. Mater. Interfaces 1, 1400359 (2014) [4] D. König, S. Gutsch, H. Gnaser, M. Wahl, M. Kopnarski, J. Göttlicher, R. Steininger, M. Zacharias, D. Hiller, Sci. Rep. 5, 09702 (2015) {open access} [5] A.R. Stegner, R.N. Pereira, R. Lechner, K. Klein, H. Wiggers, M. Stutzmann, M.S. Brandt, Phys. Rev. B 80, 165326 (2009) [6] G.M. Dalpian, J.R. Chelikowsky, Phys. Rev. Lett. 96, 226802 (2006) [7] J. Ibanez, S. Hernandez, J. Lopez-Vidrier, D. Hiller, S. Gutsch, M. Zacharias, A. Segura, J. Valenta, B. Garrido, Phys. Rev. B 92, 035432 (2015)

Resume : The plasmon enhanced photoluminescence of fullerene C60 thin film was studied to reveal the dependence of the strength of gap plasmonic field in coupled nanosystem “Au nanoparticles monolayer / C60 film / Al film” on the thickness of fullerene spacer in the thickness range of 10 – 95 nm. The non-monotonic dependence of the photoluminescence enhancement factor with minimum at the fullerene film thickness of 50 nm was observed. Such dependence was explained as the result of excitation of the propagating surface plasmon polaritons in Al film by the near field of localized surface plasmons of Au nanoparticles. The surface polaritons excitation leads to additional radiative damping of plasmonic oscillations in Au NPs that causes decrease of the enhancement factor of the fullerene photoluminescence intensity. Correspondingly, 50 nm was considered to be the gap thickness at which the most effective excitation of surface polaritons occurs.

Resume : Memories (NVM) have been over the last 20 years key enabler technologies for microcontroller products where systems speed, security and customization are important. To overcome scaling challenges oxide-based Resistive switching memories (OxRAM) are a promising solution. The main weak points of OxRAM technologies are the high forming power, high set/reset current and the poor endurance. Recent works on the incorporation of nanocrystals (NCs) randomly positioned in crossbar OxRAMs have shown increased endurance (~109 cycles), low switching energy (720 fJ), improved VSET and VRESET uniformity, increased Roff/Ron resistive ratio (about x100), and increased yield when compared to identical OxRAMs without NCs [1]. In this work, we present an innovative solution to fabricate planar components with a very high Roff/Ron resistive ratio by coupling ultra-low energy ion implantation and a nanodamascene process. We aim at a horizontal metal/insulator/metal (MIM) with embedded NC structure. The main route to introduce self-aligned In2O3 nanocrystals only in the active junction is the selective formation of these nanoparticles depending on the matrix material. The proposed architecture will be presented and the first results about the demonstration from TEM images of this selective formation of In2O3 nanocrystals either in silica or silicon nitride will be discussed. The preliminary electrical results on micron and nanometer sized junctions will be shown. 1. W.-Y. Chang, et al., APL 95, 042104, (2009)

Resume : The infuence of quantum confnement on the electrical and optical properties of semiconductor nanocrystals has been intensively investigated in recent years. In this work we present electrical characterization of Zr doped to Si in the SiO2 matrix with different Si content. Zr, Si and SiO2 co-sputtered in the magnetron sputtering system on n-type Si wafers. After the deposition process, an annealing treatment was carried out in order to induce the silicon nanocrystals (NC) formation. Si NCs in a dielectric matrix have different band gap which changes with NC size due to the quantum confinement (QC) effect. On the other hand, Zr can do covalent bonds just like Si and its covalent radius is a little big than Si. Furthermore, when Zr comes together with O2, it can have three different forms as tetragonal, monoclinic and cubic. Zr and Si interact with O because binding energies close to each other. We studied the electrical transport through this composite structure using I-V measurements in the vertical and lateral directions. Due to the differences in the vertical and lateral organization of the nanostructures, we observed a clear difference in the carrier conductivity. This is particularly important for solar cells where the vertical transport is more crucial than the lateral transport. Zr doping changed the electrical resistivity on the as grown samples and annealed samples. Resistivity increased with increasing of Si content on the as-grown samples otherwise decreased with increasing of Si content on the annealed samples. At the annealing temperature, Si nanocrystal is formed and Zr bonds with oxygen to form ZrO2 structure.

Resume : An addition of fluorides to oxide glasses significantly changes lots of properties of oxyfluoride glasses, namely, to extend transmittance in IR region, to reduce glass synthesis temperature, to decrease refractive index. For glass-ceramic fabrication we used BaF2-BaO-B2O3 and PbF2-PbO-B2O3 glasses systems, doped 1 mol.% REF3 (RE=Nd, Eu, Er). The increase of BaF2 or PbF2 concentration decreased the energy of phonon in the glass matrix resulting in the changes of final spectral-luminescent properties of the glass. Depending on composition and heat treatment conditions we observed the formation different crystalline phases during controlled crystallization: a) phases without RE – Ba2B10O17, BaB2O4, α-PbF2, PbB2O4.; b) cubic phases of solid solutions of Ba(x)RE(1-x)F(2+x) or Pb(x)RE(1-x)F(2+x). The latters demonstrated fluorescent properties similar to those of the corresponding crystals. The Nd-doped glass-ceramics demonstrated shift of the band maximum of the 870 nm (4F3/2-4I11/2) transition towards shorter wavelengths both for the Ba-based and Pb-based materials. The Eu-doped glass-ceramics demonstrated a sharp decrease of the ratio of intensities of electron dipole 612 nm (5D0-7F2) and magnetic dipole 580 nm (5D0-7F1) transitions. In the case of Er-doped glass-ceramics we observed an efficient up-conversion with the high intensity of the green line 550 nm (4S3/2+2H11/2-4I15/2). The research was financially supported by Russian Science Foundation (grant 14-13-01074).

Resume : Cellulose is the most abundant biopolymer in nature, which consists of chains of several hundred to thousands of D-glucose units connected by 𝛽-1,4-glycosidic linkages. Over the past decades, due to the increasing interest in sustainability and green chemistry, cellulosic materials have received much attention. The composites of cellulose having metal nanoparticles as the filler material form one group of such materials that find application in many fields especially in medical diagnostics to their light and multifunctional nature and low cost. However, preparation methods of cellulose-metal nanocomposites have some disadvantages because they are generally multistep, and non-environment friendly procedures due to their requirement for some hazardous chemicals to produce metal nanoparticles and to prevent them from aggregation. In this study, mechanochemical preparation of metal nanoparticles in cellulose matrix is investigated. The metal nanoparticles are formed from their metal ion precursors via a reduction assisted by the formed cellulose mechanoradicals – the free radicals that are formed by the homolytic bond-breaking of cellulose under mechanical input in a Cryomill. The formation of mechanoradicals and changes in the crystal structure are investigated by using UV-Vis Spectroscopy, electron spin resonance (ESR) spectroscopy, and Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, and the nature and sizes of formed nanoparticles is monitored by SEM and TEM, X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS). The results show that the nanoparticles are formed in the cellulose matrix without the need for any hazardous reducing agents (typically used for nanoparticle synthesis) and are retained well in the cellulose polymer matrix, without any need for a stabilizing agent. The study also covers the results of nanoalloy making by mechanochemistry and the formation of ‘triple nanocomposites’; namely cellulose-metal nanoparticle-synthetic polymer composites.

Resume : Principles of tribology at micro or nano dimensions are very different than those in macro world because the ratio of surface forces to volumetric (or bulk) forces scales inversely with physical dimensions of the objects. For micro systems with moveable parts, changes in surface forces become very crucial, they effect the operation of the system and limit their development into efficient systems. For example; many microsystems such as gears, motors, and shutters cannot be used in common commercial devices since their failure is unavoidable within a short time of operation because of stiction of the surfaces. To solve stiction problems in such micro systems, all physical and chemical events related with tribology has to be revealed first. These events, however, usually involve complex mechanisms that originate from the fact that both physical and chemical processes can take place simultaneously during rubbing or contacting of the two surfaces, e.g. of moving polymer pieces. One of these events complex events is the surface charging, also known as tribocharging. [1] In this study, we aim to show that friction forces due to adhesive forces, e.g. stiction, on micro structures’ surfaces are highly affected by the generation of electrostatic (triboelectric) charges, which are also produced as a result of (mechano)chemical changes on surfaces upon friction. To verify this, first, (previously underestimated) relation between tribocharges and coefficient of friction will be stated by simultaneously measuring the both in a modified microelectromechanical system. A micromechanical system will be built using metal nanoparticle-polymer composite material, tribocharging and stiction will be investigated for this micromechanical system. As a complementary study, the occurrence of physical changes involving chemical changes, i.e. material transfer from a rubbed polymer to a metal or other polymer surface will be investigated to show the ‘heterogeneous” charge distribution of triboelectricity in friction. Then, charging and discharging the surfaces sequentially will help to control the friction on the microsystem. An external ion source will be used to control the friction (either increase or decrease) between the triboelectrified surfaces. References : [1] H. T. Baytekin, A. Z. Patashinski, M. Branicki, B. Baytekin, S. Soh, B. A. Grzybowski. Science, 303, 308-312, (2011).

Resume : Nanostructures have been attracting lots of attention both for fundamental physics studies as well as applications in photonics, renewable energies, and sensing. A great variety of different nanosized materials have been synthesized up to date. Among different materials, carbon nanotubes (CNTs) show extraordinary electronic, mechanical, thermal, optical, and optoelectronic properties, and has great potential in next-generation electronics, optics, and optoelectronics. On the other hand, silica nanoparticles (SiO2) have attracted a keen scientific interest due to their fundamental and practical importance in materials science. Nanostructure based on silica nanoparticles has found extensively applications in areas like optoelectronic devices, photonic crystal, and chemical/biological sensor. Development of hybrid nanostructures can significantly expand the complexity and functionality of nanomaterials and offers new advantages. These hybrid nanostructures are promising candidates for the development of high performance devices. However, to construct hybrid nanostructures, challenges exist in the controlling of composition, morphology and structure of different nanoscale. Herein, we have successfully developed an environment-friendly method for generating new polymer nanocomposites using CNTs/SiO2 hybrids as reinforcing fillers. This method is based on the covalent bonding interaction between carboxylic acid-functionalized carbon nanotube (CNT-COOH) and amino-functionalized silica nanoparticles (SiO2-NH2). Indeed, amino-functionalized silica nanoparticles were prepared by a silanization with 3-aminopropyltriethoxysilane, while carboxylic acid-functionalized carbon nanotubes were prepared by acid treatments. In this study, we describe the preparation of carbon nanotube – silica – PVA composites films. The dispersion and morphology of hybrid nanostructures were investigated by Scanning Electron Microscopy and Transmission Electron Micrographs. Optical, electrical and mechanical properties reflect dramatic changes as a function of particle size and weight fraction of these nanostructures, especially when reaching the onset of percolation. The method we have developed opens up a wide range of possibilities and applications in the electronic and optoelectronic sector.

Resume : Integrated photonics has since long pursued an efficient and monolithic light emitter compatible with the current Si-based microelectronics. In this respect, rare earth (RE)-doped oxides have attracted considerable attention for being used within the telecommunication (Er) and visible emission (Ce, Tb and Eu) ranges. Conventional chemical and physical deposition methods result in a lack of inter-RE ion distance control, which may lead to RE clusterization. The so-called delta-doping approach, which consists in the alternated deposition of subnanometric RE and oxide layers, has proved to solve this drawback. Here, we present the structural, optical, electrical and electro-optical properties of multilayered Al/Tb/Al/SiO2 systems fabricated using the delta-doping approach by means of electron beam evaporation on p-type Si wafers and annealed at different temperatures. Transmission electron microscopy and electron energy-loss spectroscopy confirm the multilayered structure, being the Al/Tb/Al stack homogeneously mixed. X-ray photoelectron spectroscopy analysis revealed the oxidation of both Tb and Al. Photoluminescence studies determined an increase of one order of magnitude increase in the Tb+3 emission when Al is present, as Al induces the RE oxidation in the trivalent conformation. Finally, the multilayers were embedded into a metal-oxide-semiconductor structure depositing ITO on top and Al at the bottom, from which intense green electroluminescence from Tb+3 ions was detected.

Resume : During the last decade, luminescent semiconductor nanocrystals (NCs) have attracted extensive research interest for ultrasensitive and multiplexing applications in optical sensing, specifically for heavy ion detection. The latter is commonly based on the capability of heavy ions to reduce photoluminescence (PL) intensity of NCs being adsorbed at their surface. In this work, the results of study of the effect of quenching of PL intensity of thiol-stabilized water-soluble ZnS-coated AgInS2 NCs in the presence of Pb2+ ions are presented. The factors influencing the efficiency of quenching process such as NCs dilution, pH value, composition and concentration of working buffer solution were studied. It is found that the increasing of NCs dilution and acidity of buffer solution promotes PL quenching by Pb2+ ions. In all media used, the decrease of PL intensity in the presence of Pb2+ ions was accompanied by a red shift of the PL band. In 0,5 mM citrate buffer solution, the red shift reached almost 5 nm. The degradation of the PL intensity is attributed to formation of some substances at the NC surface acting as the centers of nonradiative recombination. The red shift is ascribed to different effect of metal ions on the PL intensity of NCs of different sizes. The bimodal distribution of the NCs is proved by the PL study of NC fractions separated by ultracentrifugation. The obtained results could be useful for development of novel methods for detection of heavy metal ions.

Resume : Silver nanocrystals (Ag-NCs) are of considerable interest for a wide range of applications including medicinal (cancer therapy, drugs delivery, diagnostics…) and antibacterial purpose but also for sensing, catalysis and photovoltaics (PV). In this work we are interested in Ag-NCs for their plasmonic properties, which are highly relevant for enhancing optical absorption of solar cells. In particular, Ag-NCs are expected to improve the efficiency of third generation solar cells based on frequency conversion layers, containing rare earth and/or silicon nanocrystals (Si-NCs). Ultra-Low-Energy Ion-Beam-Synthesis (ULE-IBS) is an interesting technics to obtain 2D arrays of Ag-NCs embedded in a dielectric matrix and with controlled sizes, densities and positions. However, the NCs nucleation and growth are strongly dependent on the matrix characteristics. In this work we investigate the synthesis of Ag-NCs by ULE-IBS in different dielectric matrices, such as silicon oxide and nitride doped with rare earth ions (Tb+, Yb+) and/or containing Si-NCs. The structural characteristics of Ag-NCs will have been investigated by HREM and EFTEM and their dependence on the matrix composition and on its integrity (presence of defects, porosity, strain…) will be discussed, as well as the impact of the Ag-NCs characteristics on the system optical properties, in particular on the PL emission of the rare earth and/or Si-NCs.

Resume : Electrical properties of doped Si1-xGex nanocrystals embedded in SiO2 A.Chelouche, G. Ferblantier, D. Muller, D. Mathiot ICube, CNRS-Unistra, 23 rue du Loess, 67037 Strasbourg Cedex 2, France We have recently shown that ion beam synthesis by co-implantation of Si, Ge and (As or P) is an efficient way to form doped Si1-xGex nanocrystals (NCs) embedded in SiO2 [1]. In the present study, we show the influence of the dose and the nature of dopants on the electrical properties of MOS structures including such doped Si1-xGex NCs. The various species (Si, Ge and As or P) were implanted in this order into a 170 nm-thick SiO2 film thermally grown on a (100) Si(n) substrate. The implantation energies (35 keV for Si and P, 70 keV for Ge and As) were chosen to obtain the same projected range (about 50 nm from the top surface) for the three implanted elements. As a typical case, we used doses of 1x1017 and 8x1016 cm-2 for Si ang Ge respectively. Two different doses of arsenic (1x1016 and 3x1016 cm-2) and one dose of phosphorus (3x1016 cm-2) were used to compare the doped NCs with the undoped Si1-xGex NCs, and to study the influence of the nature of dopant (As/P). A single thermal anneal at 1000°C was used to drive the NCs formation. MOS structures were then obtained by evaporating small Al electrodes on the top of the SiO2 layer including the NCs, whereas blanket Al evaporation was used for the back contacts of the Si substrate. Hall effect measurements were also performed on some samples. The I(V), C(V) results obtained on the MOS structures, as well as the Hall effect results, strongly support the effectiveness of the doping of the NCs. [1] A. CHELOUCHE, G. SCHMERBER, G. FERBLANTIER, D. MULLER, D. MATHIOT, Ion beam synthesis of alloyed Si1-xGex nanocrystals embedded in SiO2, Ion Beam Modification of Materials (IBMM 2016), Wellington (NZ), oct-nov. 2016

Resume : Nano-sized Rare Earth oxides, including Dy2O3, La2O3, Nd2O3, Pr6O11 nanopowders are prepared by an azeotropic co-precipitation method. The as-prepared nanoparticles after calcinations are well dispersed. Ba1-xCax(Ti1-yZry)O3 - Rare Earth oxides (BCTZ-RE) lead-free piezoelectric ceramics doped with the as-prepared nano-sized Rare Earth oxides?0.1wt% - 1.0wt%) were synthesized at 1480? to 1500? for 2 hours using traditional solid-state sintering method. The influence of nano-RE oxides doping on microstructure and electrical properties of BCTZ ceramics were investigated. X-ray diffraction analysis showed that all the BCTZ ceramics still exhibited perovskite structure with the addition of nano-RE oxides. The high sintering ability of the nanoparticles effectively decrease the sintering temperature of the BCZT ceramics comparing with those of BCZT ceramics with micro-sized RE oxides doping. The Curie Temperature of BCTZ-RE piezoceramics decrease, as same as the micro-sized RE oxides doping system. The ceramics show typical diffuse phase transition and dielectric relaxor. The improvement in the dielectric properties and piezoelectric constant of the BCTZ-RE ceramics can be achieved. Key words: nano particles; Rare Earth Oxides; BCTZ; electric properties.

Resume : Recently, halide perovskite CsPbX3 (X=Cl, Br, I) nanocrystals (NCs) have attained great attention as the candidates for optoelectronic devices due to their outstanding electrical and optical properties. CsPbX3 NCs facilitate highly efficient light generation due to the wide color tunability (400-800 nm), narrow full width at half maximum (FWHM) of emission (~ 20 nm), and high photoluminescence quantum yields (PLQYs) but also these low economic and energetic costs. In order to realize wide color gamut (WCG) and high color rendering index (CRI) of the white LEDs, many researches about high purity green emitting material have been studying. In this study, we successfully synthesized high quality green (Cs0.4Rb0.6)PbBr3 colloidal perovskite NCs with a FWHM of 21.4 nm and an absolute PLQY of 99.7% by simple hot-injection method. PL properties were enhanced and emission peak was shifted towards to shorter wavelength by substituting Rb ions. Subsequently, (Cs0.4Rb0.6)PbBr3 NCs was integrated with mesoporous silica to improve the thermal stability of the perovskite NCs on InGaN LED chip with increasing forward-bias current. Finally, we optimized luminescence properties of the white light generation in the application of LEDs.

Resume : We have fabricated the Au-C mixture membrane inside the drilled aperture by using electron beam irradiation. Regardless of the surface treatment on the FIB drilled aperture, we found Au atoms diffuse together with carbon atoms, resulting in the uniform membrane. The impurity in the Au-Au binding is reported provide the enhanced binding. Drilling a vacuum deposited Au film can be rather difficult and did not present the consistent results due to size dependent irregular melting temperature. Hence, we fabricated uniform Au-C binary mixture membrane, followed by FIB drilling. We obtained a pore with its diameter less than 5 nm. The fabricated pore along with Au particle on the membrane can be utilzed as plasmonic optical nanopore

Resume : The transparent inorganic glass–ceramics phosphor converting (PC) layers is an alternative way to conventional polymer-based PC, especially for the case of high-power WLEDs. We elaborated and studied properties of the PC composed of the glass matrix and embedded micro/nanocrystals. The low temperature (melting temperature of un-doped glass is 1277oС) glass-ceramics based on lithium- germanium oxides Li2O-x(GeO2) (LGO) as optical materials practically had not been studied yet. The devitrification of the Li2O-x(GeO2) low temperature glass-ceramics start at 512 С. Heating leads to formation of ordered areas of the Li2Ge4O9 micro/nanocrystals in the volume of amorphous GeO2 body, in other words, the glass-ceramics is formed. The Li2Ge4O9 phase diminished when temperature riches T = 567 C, then the Li2Ge7O15 phase is formed. The LGO glass-ceramics doped with ions of Cr, Eu, and Nd ions were made and studied. Some correlation between morphology, conductivity and optical especially luminescent properties has been discussed. Selection of the conditions of the glass heat treatment makes possible to obtain high dispersive states of different composition, morphology and physical properties of which are determined by the chemical composition and phase’s structure, by the relative volume and size of ordered regions, by the character of their spatial distribution. The subsequent cooling stabilizes such dispersion states and allows preparing materials of desired composition and properties.

Resume : Silicon nanoparticles (SiNPs) are synthesized by implanting 70 keV Si-ions into a SiO2 thin-film on Si-wafer followed by thermal annealing. Hydrogen, which is known to passivate dangling bonds and enhance the luminescence of SiNP [1], is introduced by i) forming gas annealing (FGA: 93% N2+7% H2), and ii) by implanting 7.5 keV H-ions at a fluence range corresponding to a peak H-concentration of 0.02-2 atomic %. Nuclear reaction analysis (NRA), using the 1H(15N,"αγ" )12C-reaction, technique is used to quantify the H-concentration [2], and photoluminescence (PL) spectroscopy is performed to observe the SiNP PL. It is found that H-concentrations down to 50 ppm are traceable by the NRA technique. After Si-implantation enhanced hydrogen concentrations are observed. After FGA, H is evenly distributed in the SiO2, while the implanted H-concentration basically follows the implantation profile. From PL spectroscopy, implanted hydrogen is found to reduce the SiNP PL, as well as to introduce new defect PL with increasing H-fluence. After a low-temperature N2-annealing, the SiNP PL for H-implanted samples improves somewhat, but FGA is still more effective than H-implantation to passivate dangling bonds, resulting in higher SiNP PL, even though the significant H-uptake via FGA is low. [1] E. Neufeld et al., Thin Solid Films, 294 (1997) 238-241. [2] M. Wilde and K. Fukutani, Surf. Sci. Rep., 69 (2014) 215.

Resume : Ge nanocrystals (NCs) in oxides for nonvolatile memories is a topic of great research interest. The performance of NCs memories is strongly morphology-dependent and can be improved by tailoring Ge NCs size and density (modifying annealing conditions [1]) or by changing NCs spatial distribution (using multilayers [2]). Here, we demonstrate the high performance of trilayer memory capacitors with floating gate (FG) of Ge quantum dots (QDs) arranged in a 2D array. The capacitors were obtained by depositing gate HfO2/Ge-HfO2 intermediate layer/tunnel HfO2 layer sequence on p-Si wafers using magnetron sputtering followed by rapid thermal annealing for Ge and HfO2 nanostructuring. HRTEM, HAADF-STEM, SAED and XPS investigations were correlated with measurements of C–V loops and charge retention time curves (C–t). Our capacitors have a FG of 2D array of well separated Ge QDs in crystalline HfO2, located at fixed position in respect to Si substrate. Ge QDs have 2–3 nm diameter, 4–5 x 1015 m–2 density and are separated to each other by ~8 nm (as Ge QDs are formed at boundaries crossing of ~8 nm HfO2 NCs in FG). This FG morphology produces enhanced memory properties due only to charge storage in Ge QDs, i.e. memory window of ~4 V (C–V loop) and capacitance decay of 14% in first 3–4 x 103 s followed by very slow decrease (C–t curve) that reaches 50% after 10 years by extrapolation. References: [1] Scripta Mater. 113, 135 (2016); [2] Appl. Phys. Lett. 107, 093102 (2015)

Resume : Rare earths doped Si-based materials have been applied as suitable active hosts for many applications, such as lighting, photovoltaics and microphotonics. In this last field, Er has been widely used due to its optical emission at 1.54 m that falls in a window of minimum losses for silica optical fibers. To overcome the limits of its low excitation cross section and low solubility in Si-based hosts, two approaches have been pursued in this work. First, the use of Er-Y mixed silicate thin films was proposed to dissolve high amounts of optically active Er ions in Y substitutional positions. Furthermore, the additional introduction of a proper sensitizer, such as bismuth, was demonstrated to increase the Er excitation cross section. After thermal treatments in O2 and N2 environment, the presence of small nanoparticles (NPs), about 6 nm in diameter, was evidenced by transmission electron microscopy. The chemical nature of the NPs was discerned by means of energy dispersive X-ray and electron energy loss spectroscopy performed with nanometric resolution. In particular the metallic NPs were formed in the N2 environment and Bi silicate in O2. While the Bi NPs are strongly detrimental for Er emission, the Bi silicate NPs have been demonstrated to act as efficient sensitizers for Er ions, by improving Er emission up to 250 times with respect to the resonant condition. These results suggest (Bi + Er)-Y disilicate as a good candidate for applications in microphotonics.

Resume : Graphene is a very promising material with very interesting properties having a huge amount of new applications in many sections of every day life. Nevertheless, graphene as a material for micro/nano-electronics is still not grown directly on a semiconducting substrate. The only way to achieve this is the use of epitaxy on SiC substrate, a method where extremely high temperatures are required (>1200 degC). The aim of this research is to found and alternative way to grow Graphene layers on SiC substrates at temperatures < 1100 degC. The implantation experiments were implemented in a medium energy, medium current ion implantation tool at 60 KeV with fluence (a) 5E15 and (b) 1E16 ions/cm2. The annealing experiments carried out in a rapid thermal annealing (RTA) tool. The RTA conditions were 1100 degC at pressure 1E-4 Torr. The 4H-SiC carbon terminated implanted samples were characterized by Raman and TEM techniques. TEM characterization involves HR-TEM, XTEM/Cs-corrected and PV-TEM. The TEM observations of nanocarbons need special observation conditions at low voltage (below 100 kV typically) to avoid their damage by the electron beam. HR-TEM . defocused micrographs revealed the damaged area of SiC substrate, estimated to 134 nm. In addition, HR-TEM micrographs shown the presence of nanocrystalline Si regions. Such regions were observed below the SiC damaged region and coexist with nanocarbon (graphene) domains. In conclusion, we demonstrate that the nano-graphene domains can be fabricated. However, optimization of the ion implantation conditions are required in order to avoid the formation of Si-nanocrystals and the to fabricate the nano-graphene regions on the surface of SiC substrates.

Resume : In recent years, the investigation of the ZnO-based solar cells has attracted more attentions due to the low fabrication process and appropriate electrical efficiency provided by this technology. Unfortunately, ZnO as an absorber layer is quite restricted in visible and IR ranges due to its wide band gap value and the requirement of new approaches to improve the absorbance behavior for infrared and visible lights. Thus, in order to deal with the growing high conversion efficiency requirement, it is very important to develop new approaches and designs to achieve better trade-off between the electrical efficiency and manufacturing cost. In this paper, a new approach based on metallic nanoparticles engineering aspect is proposed to achieve superior absorption for ZnO-based solar cell. The overall device performance comparison with three different metallic layers (Au, Ti, and Ag) is performed numerically. We find that the power conversion efficiency is considerably enhanced as compared to the conventional design. Moreover, the proposed design is optimized design using particle swarm optimization (PSO) approach in order to achieve higher optical and electrical performance of the device. The obtained results make the proposed design methodology as a potential alternative for developing low cost and high performance solar cells.

Resume : Gallium selenide (GaSe) belongs to the large class of layered semiconductors. It is a promising material for usage in THz electronics, as the basis of various optoelectronic devices, a matrix for hydrogen storage, substrates in planar nanotechnologies, etc. In this communication we demonstrate that anodic oxidation of GaSe cleaved surface (0001) in aqueous solution of sulfuric acid results in formation of semiconducting GaSe0.75S0.25 nanoparticles (average diameter of 35 nm) embedded in selenium dioxide dielectric matrix. The processes of the van der Waals GaSe (0001) surface destruction and GaSe0.75S0.25-SeO2 nanostructured system formation are investigated by X-ray diffraction and Atomic-force microscopy. Electrical properties (AC and DC conductivity, current voltage characteristics, frequency dependence of dielectric permittivity) of the obtained GaSe0.75S0.25-SeO2 system are under consideration. Also it is shown that exposure to water of GaSe0.75S0.25-SeO2-GaSe samples under daylight illumination at room temperature leads to formation of another nanostructured system on the surface of GaSe consists of Ga2O3 nanoparticles embedded in a composite dielectric matrix (selenium oxides, gallium selenate and gallium seletite).

Resume : Indiun selenide (InSe) form a class of two-dimensional layered semiconductors is a promising material for usage in THz electronics, as the basis of various optoelectronic devices, a matrix for hydrogen storage, substrates in planar nanotechnologies, etc. As follow from a number of investigations, InSe also can be used as initial material for different types of nanostructures formation. Particularly, the possibility to form In2O3 nanowires by thermal oxidetion of InSe was previously shown. In this communication we demonstrate that high intensity illumination on air saturated with water vapour at room temperature leads to formation of In nanoparticles (average diameter of 20 nm) embedded in diselenium pentoxide dielectric matrix on the cleaved surface (0001) of InSe single crystals. Electrical and dielectric properties of such In-Se2O5 nanostructured system have been investigated. It is found a field (E) stimulated switching from a low- (with typical for space-charge-limited current at low E and Schottky emission at high E current voltage characteristics) into high-resistivity state (with typical for resonance tunneling structures Z- and N-shaped I-V characteristic) and memory effect. Also it is found a negative capacitance effect in a low-frequency range (0.4-0.8 MHz). The qualitative model for interpretation of experimental results is under consideration.

Resume : Environmental considerations allied with technological and scientific challenges have attracted a search for energy-efficient processing routes for advanced functional nanomaterials. We present a high-energy ball milling technique for large-scale synthesis of nanoparticles and nanomixtures with no solvent requirement, which can be used as catalysts for alkane and alcohol oxidation reactions without any additional refinement. The resulting nanomaterials have been fully characterized by TEM, SEM, EDX and XPS. The proposed synthesis route by ball milling is an effective green process for nanomaterials production, providing a simple, sustainable and economical production method for the development of highly efficient and practical catalysts.

Resume : Localized surface plasmons (LSP) can be excited in metal nanoparticles (NP) by UV, visible or NIR light and are described as coherent oscillation of conduction electrons. Taking advantage of the tuneable optical properties of NPs, we propose the realization of a plasmonic structure, based on the LSP interaction of NP with an embedding matrix of amorphous silicon. This study is directed to define the characteristics of NP and substrate necessary to the development of a LSP proteomics sensor that, once provided immobilized antibodies on its surface, will screen the concentration of selected antigens through the determination of LSPR spectra and peaks of light absorption. Metals of interest for NP composition are: Aluminium, Gold and Iron. Recent advances in nanoparticle production techniques allow almost full control over shapes and size, permitting full control over their optical and plasmonic properties and, above all, over their responsive spectra. Analytical solution is only possible for simple NP geometries, therefore our analysis, is realized recurring to computer simulation using the Discrete Dipole Approximation method (DDA). In this work we use the free software DDSCAT to study the optical properties of metal nanoparticles embedded in an amorphous silicon matrix, as a function of size, shape, aspect-ratio and metal type. Experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.

Resume : New lasers and amplifiers based on rare-earth (RE)-doped silica optical fibers need improved spectroscopic performances: gain curve engineering, mitigation of photodarkening, enhanced spectral coverage, etc. In this context, a route of interest consists of embedding RE ions within nanoparticles of composition and structure different from those of silica. Therefore, optical fibers were prepared by doping the preform with already made LaF3:Tm3 nanoparticles. While nanoparticles are observed in the fibers, XPS measurements performed on the samples give no signal at 685.30 eV (corresponding to the energy of the F1s photoelectron); consequently, the core of preforms and optical fibers are fluoride free. In order to bring out the reactivity of LaF3 in the fibers matrix at high temperature, Thermo-Gravimetric Analyses, Energy Dispersive X-ray Spectroscopy and Raman spectroscopy were carried out for LaF3, SiO2 and GeO2 which are present in fibers context, and their mixture with different molar ratios. The results show that the fluoride reacts with the metals M (Si or Ge) at high temperature to liberate the metal tetrafluoride gas leading to a new product A. It was observed that the composition of A is strongly related to starting mixture. Following these results, we infer that the fluoride evaporates while the porous layer is sintered during the fabrication of the preform. The phase identification of A will be helpful to determine the nanoparticles composition observed in the fibers.

Resume : Silicon nanocrystals (SiNCs) embedded in SiO2 have been extensively studied because of their potential to fabricate novel optoelectronic and photonic devices. Their optical properties are strongly affected by both their size and local environment. In this work the optical and structural properties of SiNCs have been studied under high-hydrostatic pressure, with the aim of exploring the effect of the surrounding matrix on the phonon and band-gap pressure coefficients of the NCs. Raman scattering and photoluminescence (PL) measurements have been performed on two different types of samples: matrix-embedded SiNCs/SiO2 (ME-NCs) and free standing SiNCs (FS-NCs). The experimental pressure coefficients of the PL bands for the latter are compatible with indirect band-to-band emission from the fundamental and higher-excited states of the SiNCs. Also, the pressure behavior of the phonons of the FS-NCs is virtually identical to that of bulk Si. In contrast, in the ME-NC sample the phonon pressure coefficient reveals a pressure amplification effect due to the larger compressibility of the SiO2 matrix relative to Si. In this case, the PL measurements under high-hydrostatic pressures show two emission bands that exhibit different pressure behaviors. The low-energy emission can be ascribed to localized states, while the pressure dependence of the high-energy emission turns out to be virtually identical to that of bulk Si when the pressure amplification effect induced by the SiO2 matrix is considered. In order to better understand and constrain the effect of pressure on the structural properties of the NCs, we have also performed theoretical calculations based on density functional theory and elastic continuum theory to evaluate the compressibility of the NCs as a function of size and of the type of matrix.

Resume : Barium Titanate BaTIO3, due to its peculiar crystal structure finds wide applications in various fields of electronics. Recently these materials are also explored as the piezoelectric materials in nano-generators and other energy harvesting applications. To add to it, BaTiO3 is also an attractive host for the doping of lanthanide ions and find its applications in integrated light-emission devices, field emission displays, lasers etc. Eu3+ when introduced in BaTiO3 phosphor have interesting luminescence characteristics with wavelengths in the red regions. Generically BaTiO3:Eu3+ is synthesized through a high temperature solid state reaction. A number of alternative routes have been investigated with the aim of lowering the temperature and nano-sized product. To the best of our knowledge the lowest temperature achieved is 110 oC in the hydrothermal synthesis with special precursors and limited quantity of output. Here we report a novel and facile solid state synthesis route for the nano sized, Eu3+ activated BaTiO3 at lower temperature of 80 oC from the readily available raw materials. The X-Ray diffraction patters of the synthesized phosphor confirmed the formation of BaTiO3. The phosphor particles exhibit a size of 10-30 nm with the PL and PLE characteristics matching with the previous reports. We believe our process may pave a way for the revolutionized synthesis route for various materials, as lowers the temperature, uses readily available raw materials and the obtained product is also in good quantity.

Resume : ZnO nanowires show unique combination of properties such as wide band gap, high excitation binding energy, tunable morphology, optical transparency and electrical conductivity with great application potential in energy conversion. We prepared functionalized ZnO nanowires (NWs) with semiconductor polymer poly(3-dodecylthiophene-2,5-dilyl). The resulting inorganic-organic composites (P3DDT - ZnO NWs) contains the components in various ratios. Hybrid nanocomposite were characterized by technique of mass spectroscopy (MALDI), photoluminiscence spectroscopy, Fourier transform infrared spectroscopy (FTIR), photothermal deflection spectroscopy (PDS) and scanning electron microscopy (SEM).

Resume : The incorporation of a conductor or a semiconductor into a polymer matrix to achieve a high dielectric constant has been attempted as a way to overcome the limitations of conventional high dielectric constant composites. However, it has a fundamental problem of increase in electric conductivity and is a stumbling block to its application as a high dielectric layer. In this study, we propose a method to minimize the rise of conductivity and leakage current through core - shell nanostructure as an approach to solve this fundamental problem with obtaining the high dielectric constant. The core-shell polypyrrole@polyimde (PPy@PI) particles were prepared and investigated on their dielectric properties for all-organic dielectric composites. The individually insulated PPy nanoparticles were formed by nano-scale coatings, which were obtained through interfacial precipitation, where the negatively charged polyamic acid (PAA) interact and are precipitated on the positively charged PPy particles. PAA shell becomes PI shell on PPy particles to form PPy@PI core-shell via imidization. The core-shell structure of PPy@PAA was observed by transmission electron microscopy (TEM) with staining of particles. At the 15wt% PPy in PPy@PI composite, the dielectric permittivity of over 100 was obtained with the electrical conductivity of 10-8 S/cm. High fractional use of PPy in dielectric layer as over 30 wt% PPy gave the ultra-high dielectric permittivity of 487. The loss tangent of PPy@PI is lower than 0.18 until 15 wt% PPy content.

Resume : Development of durable, sensitive, and flexible piezoelectric nanogenerators (PNGs) with high power density and high energy conversion efficiency becomes a great challenge for next generation electronic applications. Here, we developed a flexible, sensitive, cost effective PNG, fabricated by integrating steel woven fabric electrodes into poly(vinylidene fluoride) (PVDF)/ aluminum oxides decorated reduced graphene oxide (AlO-rGO) nanocomposite film, where AlO-rGO acted as nucleating agent for electroactive β-phase formation. This PNG is able to scavenge several types of ambient mechanical energies such as body movements, machine and sound vibrations, which are abundant in living environment. The PNG generates an output voltage of ≈36 V and short circuit current of ≈0.8 μA, and the maximum output power density of ≈44.28 W/m3 under repeated human finger imparting under the pressure of ≈31.19 kPa. The PNG is able to charge the capacitor (2.2 μF) in a very short time span (≈6.1 V in 96.6 sec), which shows the ability of high energy conversion efficiency up to ≈12.47 %. The PNG can also instantly light up several colors LEDs and power up wrist watch, calculator, speaker, and LCD screen. More importantly, PNG retains its performance after long compression cycles (≈158400), demonstrating great promise as a PNG towards large-scale application in portable and flexible electronics devices.

Resume : The discovery of efficient room-temperature (RT) photoluminescence (PL) of porous silicon has motivated a tremendous number of studies on this material and also on similarly nanostructured silicon systems. Si nano-crystals (NC) in a dielectric matrix have different band gap which changes with NC size due to the quantum confinement (QC) effect. Zr can do covalent bonds just like Si and its covalent radius is a little big than Si. Furthermore, when Zr comes together with O2, it can have three different forms. In this study Zr, Si and SiO2 co-sputtered on a p-type Si wafer in a magnetron sputtering system with different Si target powers. After annealed at 1000 oC for 1 h under N2 atmosphere, as-grown samples and annealed samples were investigated with Raman and PL spectrometer which uses 532 nm wavelengt green light laser. PL peaks of the as-grown samples were observed at 600 nm and 700 nm and their intensities are low. Annealed samples have broad and high intensity PL peak at 700 nm and broad and low intensity PL peak at ~800 nm caused by Si. Because, intensity of the peak at ~800 nm increased with increasing of Si concentration. The PL results showed that nano crystals with different contents and sizes (ZrO2 and Si) were occured in SiO2 matrix. Annealing process triggered the formation of Si and ZrO2 nano crystals.

Resume : There is a growing interest in nanostructured Silicon (Si) following the demonstrated ability to tune its light emission in the near-IR and visible range via quantum confinement (QC). Thus, Si nanocrystals (SiNCs) embedded into silica thin films have been proposed as promising building block for novel optoelectronic and biosensing devices. In this context, we report on the synthesis and characterization of ultra-thin Si nanowires (SiNWs) produced by means of an Inductively Coupled Plasma (ICP) based process. These SiNWs were found to consist of an inner Si core in the 2?15 nm range covered with an outer SiO2 shell of tens of nm-thick. Since the as-collected ICP-synthesized nanomaterial contains not only the SiNWs but also massive spherical Si clusters, a protocol to sort the SiNWs has been accomplished via centrifugation. Calculations of the Svedberg coefficient, which describes the behavior of particles subject to a centrifugal force, for both Si spheres and SiNWs lead to design an effective method for the size-selection of Si nanostructures. Scanning Electron Microscopy analyses have been performed to evaluate the efficacy of the centrifugation in terms of purification procedure. The comparison with the optical properties, probed via photoluminescence before and after centrifugation, allowed to connect the observed blue-shift with the selected mean size of SiNWs. These results open the route towards the use of ICP-SiNWs for optoelectronic applications.

Resume : We present results from a study of resistance switching in silicon-rich silica – ie silicon dioxide containing an excess of silicon. We demonstrate that changes in resistance are the result of field-driven movement of oxygen, and that this can result in large-scale changes in oxide structure and stoichiometry. While resistance switching in oxides has been studied for a number of years as a route to non-volatile electronic memories, the optical response of such systems has remained largely unknown. Here we demonstrate that simple two-terminal MIM devices can be switched between different resistance states using a combination of electrical bias and optical stimulation. This opens up intriguing possibilities for novel classes of sensors. We also demonstrate neuromorphic behaviour in our devices. Our electrical measurements show that, under the right conditions, the devices can be made to emulate some of the important behaviours of biological neurons – plasticity, for example. Taken together with the light sensitivity of these resistance switches, this opens up further possibilities for the development of light-triggered neural networks for such applications as pattern recognition and image classification.

Resume : The incorporation of metal nanocrystals (NCs) within TiO2-x thin films offers advantages for adjusting a wide range of non-volatile memory properties, ranging from resistive and capacitive switching to synaptic capabilities. In this study, we demonstrate that by inserting very small NCs (~3 nm diameter) of either Pt or Ta, we can induce resistance changes over 6 orders of magnitude and capacitance changes over 2 orders of magnitude, with promising variability (coefficient of variance ~0.2) due to the local enhancement of the electric field. Indeed, the large enhancement of the switching performance and in particular the enhancement of the measured variability stems from the enforcement of the postulated percolative networks, where the switching effect takes place, into specific locations of increased electric field. Retention measurements were also performed at room and elevated temperatures (125o C ), revealing the distinguishing nature of the two resistance states. The different degree of reactivity of the two materials against oxidation as well as the formation of large energy barriers in the case of Ta NCs, could interpret the measured data pattern. The existence of hysteresis on capacitance spectra reveals the semiconducting nature of the conducting filaments (CFs). The NCs induced large resistance changes together with the gradual switching pattern observed exhibit also attractive synaptic properties offering higher design flexibility for neuromorphic applications.

Resume : Memristive materials are attracting much attention for its truly intrinsic nano character that provide solutions to the aggressive scaling in memories, electronic and photonic switches. These devices present two resistive states with huge change in resistance between them. This is attributed to nanofilamentary connections between the electrodes that appear and disappear suddenly for a given voltage value or current. The switching between the two states remembers the previous state and provides a window voltage that promotes this kind of material for application as a resistive electronic memory (ReRAM). In this contribution we demonstrate that Si-Al oxynitride (SiAlON) materials are superior to other metal and silicon oxides materials in terms of memristance, device performance and reliability. The addition of Al to oxynitride offers a large range of possible conductivities and band-gaps depending on Al concentration, and overall this material system is compatible with silicon technology. In this work, we present the structural and electrical characterization of 140-nm thick SiAlON films on p-type Si substrates. Al was used for both electrodes, using a shadow mask on top and in full-area in the bottom. A memristive behavior was observed, showing a variation of more than 5 orders of magnitude in resistivity between the low and high resistive states. The electroforming effect on the structure was analyzed by transmission electron microscopy, that exhibits bubbles on the surface attributed to oxygen migration. Compositional study was carried out by electron energy-loss spectroscopy with nanoscale resolution, showing an oxygen accumulation in the interface between SiAlON and the top electrode. Finally, a precipitate in the Al-SiAlON interface has been observed due to the diffusion of elements from SiAlON layer, which could be directly related to the formation of nanofilaments by oxygen vacancies.

Resume : Metallic nanoparticles embedded in dielectric host matrix are implemented in various devices like Single Electron Transistors, Memristors, Flash Memories and Bio sensors. Among the methods available for nanoparticles growth the ALD and PEALD growth method presents the advantage of being a large-scale well-controlled monolayer growth. Moreover this process is very convenient as nanoparticles are embedded in-situ during the dielectric matrix growth and the process occurs at low-temperature (200°C). We report here on the Pt-island growth and on the study of the structure and transport properties of the nanostructured system. First the Pt-island growth is investigated by TEM plane views performed after respectively 30, 45 and 60 PEALD growth cycles. The mean nanoisland size increases from 1.7 nm to 4.3 nm with the number of cycles, the nanoislands being crystallized and well-dispersed. Then vertical or lateral junctions of the type metal- dielectric with nanoparticles –metal are fabricated. For lateral junctions, nanogap electrodes are performed using Shadow Edge Evaporation, with a ratio of junction width to length that may be very large (up to 1000). STEM and TEM cross-sections confirm proper fabrication. Regarding electronic properties, IV temperature dependent characterization leads us to assess the main conduction mechanism, Poole-Frenkel in the Al2O3 with embedded nanoparticles whereas a Fowler-Nordheim-type conduction is obtained in the Al2O3 reference.

Resume : The present world looked in the fabrication of light weight and compressible high performance electromagnetic interference (EMI) shielding materials for adaptable application in the area of modern electronic gadgets and telecommunication devices. This study describes the fabrication of light weight compressible porous Polydimethylsiloxane (PDMS)/FRS [ferrosoferric oxide (Fe3O4) decorated reduced graphene oxide (RGO)/single wall carbon nanohorn (SWCNH)] composite through a facile method. GO was reduced by Fe in presence of SWCNH and Fe3O4 in-situ synthesized form Fe ion after reduction. FRS dispersed in PDMS and cured in a sugar cube which leached out after curing. The resultant PDMS/FRS composite got highly porous network structure, light weight and compressible property and possessed an absorption-dominated good comprehensive EMI shielding performance, possibly due to both conductive dissipation and multiple reflections and scattering of EM waves by the inside 3D conductive RGO-SWCNH network with ferromagnetic Fe3O4 nanoparticles. The shielding performance of the composite could be simply adjusted through its? compressible property by a simple mechanical compression, presenting potential for adjustable EMI shielding. Moreover, the composite shows high electrical conductive property.

Resume : Harvesting mechanical energy from surrounding environment is an efficient approach for developing self-powered electronic devices. A piezoelectric nanocomposite (p-NC) consisting of piezoelectric nanoparticles (NPs) and flexible polymer has drawn a considerable attention in this regard. In this article, a flexible, lead free, solution processable piezoelectric nanogenerator (PENG) composed of piezoelectric perovskite zinc stannate nanoparticles (ZnSnO3 NPs) and plasticized polyvinyl chloride (PVC) was fabricated using a simple, scalable, industrially feasible, and cost effective solution casting method. The fabricated nanogenerator exhibits an open circuit voltage of 40 V, a short circuit current of 1.4 µA and an overall power density more than 3.7 µW cm-2 at 35 wt% loading of ZnSnO3, and to the best of our knowledge, these values are the best values than those have been found in the literature so far on the cubic ZnSnO3 based nanogenerator. Again, we demonstrated that, the generated power from the nanogenerator could instantly light up 7 different colors commercial LEDs without using any external energy storage unit. Also, the established nanogenerator could charge a commercial capacitor (power of 2.2 µF) to 6.7 V in a very short time period of 129 s which can be utilized for powering mobile small electronics like wrist watch, LCD screen and calculator. Keywords: mechanical energy, piezoelectric nanogenerator, PVC, cubic ZnSnO3, power density

Resume : Among emergent memory technologies, Resistive Random Access Memory (RRAM) technology shows up as a suitable candidate for the next generations of non-volatile memories. The so-called resistive-switching effect is observed for metal-insulating-metal structures (in particular with metal-oxides) by applying an external electric field to the structure. Moreover, it has been reported that the integration of nanoparticles (NPs) in this devices might directly improve their performance and scalability. In this work, we report on the fabrication and characterization of RRAM devices based on In2O3 nanoparticles using CMOS-full-compatible fabrication processes in view of back-end-off-line integration for non-volatile memory (NVM) applications. The choice of In2O3 nanoparticles was made mainly because of its work function (~5eV) and band-offset with SiO2, allowing charge-retention. We fabricated two-terminal architecture devices (capacitor-like structures): Au/Al2O3/In2O3-NPs/SiO2/Si-n+, with top circular-shaped electrodes (diameter range 50µm-500µm), with NPs-diameter between 9nm-14nm and an estimated density of 3x10^8 NPs/cm^2. Current-voltage characteristics (I-V) showed bipolar switching behavior for all the fabricated devices, with ION/IOFF ratios between 10^3 and 10^5. Moreover, our best structure yields up to 24 write/erase cycles. Our results provide insights for further integration of In2O3 nanoparticles-based devices for NVM applications.

Resume : We report a simple and scalable fabrication route of a new graphene/nanoclusters hybrid nanomaterial, exploiting the self-organized growth over graphene of epitaxial flat Al clusters surrounded by a very thin nanometric Al-oxide matrix [1]. The hybrid material growth is compatible with standard microelectronics technologies. We provide experimental evidence that graphene is a unique promising alternative to skirt the challenging issue of contacting the nanoparticles one by one with external leads in the sake of developing single electron transport devices. We take advantage of this ‘flexible technics’ to develop hybrid materials combining the specific conductivity properties of graphene and the discreteness of conductivity in Al metallic cluster thanks to the Coulomb repulsion of the clusters. More specifically, well-defined Coulomb blockade oscillations in the hybrid material conductance are systematically observed up to 40 K. Interestingly, this single electron features is preserved on devices with record contact area of 100 µm² while such transport signatures are usually limited to nanoscale patterned devices in the 100 nm2 range. The single electron transport properties are robust, demonstrated with CVD as well as exfoliated graphene substrates, in vertical and planar device geometries, all exhibiting high charging energies of few tenth of meV. The scalability, ease processing and the robustness of this graphene/quantum-dots hybrid material offers new opportunities for single electronics, spintronics and quantum electronics on graphene based devices. Reference: [1] Godel et al., Advanced Materials, doi: 10.1002/adma.201604837 (2017). [2] J. Coraux, et al., Acc. Chem. Res., 46, 2193 (2013). [3] P.T. Yin, et al., Chem. Rev.,115,2483 (2015).

Resume : The quest for miniaturization in electronics systems has led to the constant search of performant thin films with a higher dielectric constant, higher linearity and lower electrical loss. This topic represents a large interest in the field of RF and microwave components. Nanocomposites based on matrix-embedded metal nanoparticles (NP) constitute a way to improve the performance of devices thanks to the properties obtained through nanosized materials. In this work, metallic Cu and Ag NP embedded in an amorphous Al2O3 matrix were deposited using a free NP generator coupled to a conventional magnetron sputtering chamber. Depending on the process parameters, NP are produced in a broad range of sizes (1-20nm) as observed by TEM analysis. Optical properties of the obtained nanostructured materials were investigated by optical spectroscopy pointing out strong resonant oscillation of NP conduction electrons (Surface Plasmon Resonance (SPR) @ 594 nm and 445 nm for Cu & Ag NP respectively) and SPR shift associated to surrounding medium. The influence of the Ag-NPs on the electrical properties of alumina matrix was investigated using different types of MIM (metal/insulator/metal) capacitor geometries. Resistivity measurements highlighted the role of the NP volumetric fraction directly correlated to the resistivity drop. Deduced capacitive characteristic values of the nanocomposite films (capacitance, electrical permittivity & tangent of losses) were obtained using impedancemeter in the frequency range of 100 Hz - 1 MHz. Strong NP doping dependencies will be shown during the presentation.

Resume : Magnetoelectric materials give the opportunity of controlling the magnetic dipole of a device by applying an electric field. This explains the renewed interest for magneto-electrics materials within the field of magnetic memories and spintronics. Nevertheless, the scarcity of the magneto-electric materials and the smallness of the magnetoelectric effects up to now prevent the expected application of these materials. Different ways to enhance the magneto-electric coefficient are therefore investigated: for instance, theoretical predictions of a magneto-electric effect enhancement under strain have recently been put for. We showed[1] a proof of-principle experiment proving that large strains due to nanoscale size reduction are very efficient for increasing magnetoelectric coefficients by orders of magnitude. We studied the archetype magnetoelectric material, Cr2O3, which was deposited in the form of epitaxial clusters in a MgO matrix that induces a large epitaxial strain in the clusters. The MgO layer is thin enough to behave as a tunnel barrier: electrons can be injected from a Fe magnetic electrode into the Cr2O3 clusters by tunnel effect. This enables us to measure the tunnel magneto-resistance effect and by this way to probe the magnetisation of those nanometric clusters under voltage. This original technique showed that the highly strained clusters exhibit an unprecedented 600% change in magnetization magnitude under 1V applied to the MgO tunnel barrier: this effect is due to the enhancement of the magneto-electric coefficient of three orders of magnitude relative to bulk Cr203. This effect goes with a large magnetic anisotropy change proportionnal to the square of the applied electric field.[2] Furthermore, a multiferroic phase, with both permanent magnetic and electric polarizations, is observed in those clusters - while bulk Cr203 is antiferromagnetic and paraelectric-. The magnetization shows for instance at low temperature, close to 10K, a continuous phase change, [3] strongly dependent on the applied electric field which could be consistent with weak ferri-magnetism. 1D. Halley, N. Najjari, H. Majjad, L. Joly, P. Ohresser, F. Scheurer, C. Ulhaq-Bouillet, S. Berciaud, B. Doudin and Y. Henry, Nature Communications, 5, 3167 (2014) 2 D. Halley, N. Najjari, F. Godel, M. Hamieh, B. Doudin and Y.Henry, Phys. Rev. B 91, 214408 (2015) 3 D. Halley, N. Najjari, F. Godel, M. Hamieh, B. Doudin and Y.Henry, Nanotechnology 27, 245706 (2016)

Resume : Well self-assembled pure and Mn-doped SnO2 nanocubes were synthesized by interface thermodynamic method, which is ideal for highly homogeneous large scale thin film deposition on flexible substrates for various electric devices. Mn-doped SnO2 shows very good resistive switching with high On/Off ratio (over 103), endurance and retention characteristics. More important, the resistive state can be tuned by multi-layer fabrication by alternate pure SnO2 and Mn-doped SnO2 nanocube layer, which improved the memory capacity of resistive switching effectively. Thus, such a method provides transparent, multi-level resistive switching for next generation non-volatile memory applications.

Resume : Ge quantum dots (QD) embedded in insulating matrix show the appealing features of a confined system with interesting properties in the light absorption processes. In particular, among quantum confinement effects, there are the increase of the optical bandgap and the enhanced oscillator strength which can be successfully used for increasing the light absorption in PV cells. In this respect, since in Ge QDs the exciton Bohr radius is larger than in Si QDs (24 nm vs. 5 nm), the modulation of the light absorption coefficient can be easier and stronger, with large potential benefits in several applications. In this work, we present an experimental investigation of light absorption in small Ge QDs (2-3 nm in diameter) grown by PECVD in a multilayer configuration (3-6 nm thick film with Ge QDs, separated by 20 nm thick SiO2 barrier). An unprecedented high light absorption efficiency, 15 times larger than in the bulk, has been observed for these systems. This light absorption enhancement in ML is confirmed by the optical fitting (based on JTL-GB model), evidencing an extremely high ε2 values in ML sample. Structural and optical characterizations have been employed to describe the QCE-induced enhancement of optical bandgap (from 0.8 in bulk up to 2.5 eV in multilayer structure) and of oscillator strength (one order of magnitude). Through a detailed electron energy loss spectroscopy (EELS) analysis we characterized the structural and chemical properties of Ge QD. A comparison with Ge QDs in single thick layer is also performed. These results add new insights into the role of QD packaging on confined systems, and open the route for reliable exploitation of QC effects.

Resume : Ge nanocrystals (NCs)/quantum dots are intensively studied for photodetectors due to extension of spectral response up to IR [1]. On the other hand, TiO2 has countless applications, e.g. solar cells [2]. In this work, we present the VIS-NIR photosensitivity of Ge-TiO2 films with Ge NCs embedded in TiO2. For this, Ge-TiO2/SiO2 buffer/Si planar structures are prepared by co-sputtering Ge-TiO2 films with different Ge contents on oxidized Si wafers followed by rapid thermal annealing (RTA) at 500–800 oC for Ge and TiO2 nanostructuring [3]. TEM, SAED and EDX investigations for films structure, morphology and composition, transmission and reflectance measurements for optical properties and measurements of spectral distribution of photocurrent and photocurrent-voltage curves for assessing photosensitivity were performed. They show that the films are formed of Ge QDs with cubic structure and of TiO2 NCs with anatase (dominant) and rutile mixture structure. By modelling optical spectra, the obtained dispersion law of refractive index shows a deep minimum at 2.5 eV due to Ge NCs (~1 eV bandgap) absorption. The films photosensitivity is in a large interval (~600–1050 nm), the photocurrent spectra of 550 oC RTA films showing a maximum at 870 nm given by Ge NCs in TiO2. We manipulate the photosensitivity band by changing Ge content and RTA temperature. References: [1] ACS Appl. Mater. Interfaces 7, 2452 (2015); [2] Nano Res. 9, 1891 (2016); [3] Appl. Surf. Sci. 309, 168 (2014)

Resume : Nanocrystals (NCs) embedded in glasses are able to enhance their physical properties or to implement new active properties. In this context copper-halide (CuCl, CuBr) semiconductor NCs embedded in dielectrics have recently attracted much attention and have shown promising applications for light emission, non-linear optics, optical information storage and optical switching.< br> In this work we report the optical response of CuCl semiconductor NCs embedded in borosilicate glasses at room temperature (RT) and when heated up to 500 ºC. The measured transmission spectra of the CuCl NCs-doped glasses at RT show an absorption band with a maximum at 367 nm. Upon excitation at 355 nm the glasses show a clear and intense photoluminescence centered at 382 nm attributed to CuCl excitonic emission. Besides the CuCl nanoparticles show a low melting point (450ºC) compared to that of the embedding glass matrix (820ºC). Taking advantage of these properties it is possible to induce reversible thermal changes related to the phase change of the CuCl NCs in the glass and detect them optically. The thermo-optical response of the composite glasses is characterized by detailed measurements of the transmission at the excitonic wavelength. It is found that upon melting there is an increase in the transmission, and there is a large hysteresis cycle (150ºC) upon melting and solidification of the NCs. Furthermore heating-cooling can be interrupted during the CuCl NCs phase change giving rise to different optical switching possibilities. The potential of developing optical switching devices in the UV region based on Cu-halide NCs systems will be discussed. < br> [1] F.E. Kalff, M.P. Rebergen, E. Fahrenfort, J. Girovsky, R. Toskovic, J.L. Lado, J. Fernández-Rossier, and A.F. Otte, Nat. Nanotechnol. 18, 1 (2016). < br> [2] D. Ahn and S.-H. Park, Sci. Rep. 6, 20718 (2016). < br> [3] I. Kriegel, C. Jiang, J. Rodríguez-Fernández, R.D. Schaller, D. V. Talapin, E. Da Como, and J. Feldmann, J. Am. Chem. Soc. 134, 1583 (2012). < br>

Resume : Organic-inorganic hybrid perovskite materials show great promise as active emitter materials for lighting, display and lasing applications due to their narrow emission, wavelength tunability and high photoluminescence quantum yields (more than 90%). Moreover, amidst the path-breaking efficiencies obtained in perovskite photovoltaics, exploration of perovskite-based light emitting diodes (LEDs) have also gained impetus. However, unlike solar cells where large grain-size polycrystalline films are desired in order to improve charge carrier extraction, LEDs require charge confinement as to aid radiative recombination. Hence, use of perovskite nanoparticles as the active emission layer is a promising route for attaining perovskite-based LEDs with high efficiency. Herein, we have used a modified ligand assisted re-precipitation (LARP) method to synthesize methylammonium lead bromide nanoparticles. The nanoparticles are then simply spin-coated to form uniform pin-hole free films. LEDs based on these nanoparticles show good current efficiencies >5 cd A-1, turn-on voltages below 3 V and maximum luminance over 3000 cd m-2. The device performance is critically influenced by the nanoparticle synthesis method as the ligands associated with perovskite nanoparticles greatly affect the electrical injection into the perovskite layer and thus the overall device performance.

Resume : We report on preparation and study of Al/LiF nanocomposite thin films for photoluminescence application. The photoluminescence can be significantly enhanced by metallic nanoparticles dispersed in the fluoride matrix. The nanocomposite is prepared by co-deposition using two methods: a thermal evaporation and a high pressure magnetron sputtering. The LiF is deposited by the thermal evaporation from a tungsten boat placed in the vacuum chamber. Al nanoclusters are formed by gas condensation of magnetron sputtered Al atoms in an aggregation chamber with enhanced Ar pressure. The aggregation chamber and the main vacuum chamber is separated by an orifice with diameter of 3 mm. The mean size of nanoclusters is controlled by both parameters: Ar pressure and the distance of Al target from the orifice. The Ar pressure is varied in the range from 20 to 100 Pa. The length of aggregation chamber is set in a range from 100 to 200 mm by shifting the magnetron head. The density of the Al nanoclusters in the fluoride matrix is controlled by deposition rate of evaporated fluoride. The size of nanoclusters is estimated using Atomic Force Microscopy and Scanning Electron Microscopy. The optical properties are studied using spectral ellipsometry and spectrophotometry. We carried out a computer simulation of the nanocomposite by means of generalized Mie model of multiparticle system. The calculated absorption effective cross-section is compared with the optical measurement. We use a blue diode laser (445 nm) for photoluminescence excitation. The effect of Al nanoparticle size and their density on photoluminescence intensity is discussed.

Resume : Cenospheres, the by-product of thermal power plants obtained from the National Thermal Power Plant, Karnataka, (typically hollow microspheres having an average size 50 µm) were cleaned by acid-base treatment. The Fe3O4-MnO2 nanoparticles were coated over cenosphere by simple two-step chemical method and characterized. The uniform coating thickness was found to be ~ 700 nm over FAC. The 5 wt% of Fe3O4-MnO2 coated cenosphere loaded polyvinylbutyral (PVB) composites were prepared by solution processing and characterized by various techniques. The dielectrics and microwave absorption property of as-prepared composites were investigated in the X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz). The effective reflection loss (RL) -10 dB (99 %) of this flexible composite was achieved for the thickness 1 mm in the X-band and Ku-band respectively. However, the microwave absorption property of this composite can be tuned by controlling thickness. High dielectric loss and synergetic effect of PVB matrix and Fe3O4-MnO2 coated cenosphere were found to be responsible for obtained low RL value. The enhancement of EM attenuation constant (α) and loss factor (LF) of this composite with frequency also indicates high EM attenuation and microwave absorption property. Further, microwave absorption property of the as-prepared composite can be improved by introducing the little amount of PEDOT: PSS in the PVB matrix. This composite film can be considered as a novel high microwave absorbing inexpensive coating material for radar, microwave engineering, communications, robotics as well as unmanned vehicles.

Resume : We investigated the feasibility of activating coherent mechanical oscillations in lasing microspheres (µS) by modulating the laser emission at a mechanical eigenfrequency. 1.5%Nd3+:Barium-Titanium-Silicate µS with diameters around 10-60µm were used as high-Q whispering gallery mode lasing cavities. The pump-probe setup includes a pump laser at 808nm modulated in the range 0.5-20MHz to excite the Nd ions, and a tunable probe laser at 1.5µm launched in a fiber into optical contact with the µS. We used three µS with different diameters. They all achieved lasing regime. The probe laser transmission spectrum showed a complex mode structure with typical thermo-optic nonlinearities and bistabilities and spectral shifts as high as 2nm. Measured Qs exceeded 10^6. In pump-off configuration, thermally driven motions of mechanical modes appear as peaks in the 50-70MHz range. As expected, the mechanical mode frequency decreases with µS size. In pump-on/probe-off configuration the peak intensity quenches at about 10MHz, in fact, it is related to laser emission. In pump-probe configuration, a peak at the modulation frequency and its harmonics are observed. The peak intensity decreases with frequency, but it is clearly visible up to 20MHz. This modulation is not related to lasing or pump scattering. The dynamics of thermal effects is usually much slower (KHz range), so we associate this effect to another non-linear mechanism such as free-carrier dispersion due to a multiphoton absorption process.

Resume : An ultrathin nonlinear optical (NLO) organic surface comprised of numerous self-assembled frustum-shaped whispering-gallery mode resonators displays both two-photon luminescence and second-harmonic generation signals. A super-second-order increase of the NLO intensity with respect to pump power confirms the microlasing action and practical usefulness of the NLO organic surfaces.

Resume : Surface plasmons (SPR) are used in a wide range of biochemical sensors. The central idea is to strongly confine the incident light in the form of an evanescent wave on a metallic surface. This evanescent wave will serve as a nanometric probe, sensitive to the optical thickness at the surface of the metal. The SPR sensors can thus be seen as optical microbalances [1,2]. The advantages provided by this technique are well known: non-destructive, real time, insensitivity of the system to perturbations far from the surface and low technical complexity. Since the first commercial devices were introduced in the early 1980s, SPR sensors have become a standard in the study of biochemical interactions [3,4]. In this presentation, we will talk about a very promising path of research that combines nanoparticle networks with the uniform gold layer [5], traditionally used in these SPR sensors, to significantly improve performance and, above all, extend measurement capabilities. The different optical modes of interrogation will also be discussed. [1] J. Moreau, J-P Cloarec, P. Charette, M. Goosens, M. Canva and T. Vo-Dinh Surface plasmon resonance imaging sensors: principle, development, and biomedical applications – example of Genotyping, volume 2 of Biomedical Photonics handbook, second edition, CRC Press [2] J. Homola. Surface plasmon resonance based sensors, volume 4 of Springer Series in Chemical sensors and biosensors [3] S. Scarano, M. Mascini, A. Turner and M. Minunni, Surface plasmon resonance imaging for affinity-based biosensors, Biosensors&Bioelectronics, 25(5), 957-966, 2010 [4] A. Abbas, M. J. Linman and Q. Cheng, New trends in instrumental design for surface plasmon resonance-based biosensors, 26(5), 1815-1824, 2011 [5] M. Sarkar, M. Besbes, J. Moreau, J.-F. Bryche, A. Olivéro, G. Barbillon, A.-L. Coutrot, B. Bartenlian, M. Canva. Hybrid Plasmonic Mode by Resonant Coupling of Localized Plasmons to Propagating Plasmons in a Kretschmann Configuration, ACS Photonics, 2(2), 237-245, 2015

Resume : We show that strong coupling can be achieved between a molecular excited state and plasmonic modes of silver hole arrays with a resonant frequency very close to the asymptotic line of the plasmonic dispersion relation, at the nonlinear regime. This strong coupling can be achieved between the two sub-systems at low molecular densities with negligible damping of the electromagnetic field. Upon coupling, new hybrid states are formed, lower and higher polaritons. This novel system encompasses new characteristics together with those of the two sub-systems. With an increasing of the molecular densities, asymmetric splitting is observed giving rise to enhanced transmission through metallic hole arrays. We reach the strong coupling regime using an extremely low molecular concentration of 0.2 mM and an absorbance of about 0.015, an order of magnitude lower than those used in other studies. The molecular system used has a transition state that lies within the nonlinear region of the plasmonic dispersion and therefore very low molecular densities could be used. Moreover, we have also succeeded in reaching a linear dependency of the Rabi splitting value on the square root of the molecular density, another proof for strong coupling. Our results are supported by rigorous numerical simulations showing that the strong coupling is observed when the molecular transition lies within the nonlinear regime of the dispersion relation.

Resume : Recently, plasmonics materials became of great interest for the elaboration of new devices for biosensing applications[1]. Indeed, they present many advantages such as the in-situ and label-free measurement, the immunity to electromagnetic interferences and good sensitivity. Plasmonic devices take advantage of the collective oscillation of electron in a metallic substrate which is very sensitive to any change in refractive index at the surface. Furthermore, the functionalization of gold substrates by receptor molecules allows high specificity for the analyte detection[1]. Many configuration of biosensors were developed, but the main limitation is most often the detection limit which does not allow the precise detection of small molecules in very low concentration, below pM[2]. Here, we present a biosensing platform based on hierarchical assembly of iron oxide nanoparticle. Magnetic nanoparticles are synthetized by thermal decomposition which leads to an efficient control of the size, ranging from 5 to 25 nm[3]. The assembly is then achieved by copper azide-alkyne catalyzed “click” chemistry by functionalizing nanoparticles and substrates by specific functional groups which lead to an irreversible and highly stable binding[4]. Functional groups located on the nanoparticle surface, allow to graft easily a variety of biomolecules which act as receptors, namely proteins, antibodys, DNA strands or nucleosides. Moreover, the fine control of the film structuration is achieved with this strategy, especially by modulating the size and density of nanoparticles which allow tuning plasmonics properties thanks to the high refractive index of iron oxide[5]. [1] Estevez, M. C.; Otte, M. A.; Sepulveda, B.; Lechuga, L. M., Analytica chimica acta, (2014) 806, 55. [2] Lafleur, J. P.; Jonsson, A.; Senkbeil, S.; Kutter, J. P., Biosensors & bioelectronics, (2016) 76, 213. [3] Baaziz, W.; Pichon, B. P.; Fleutot, S.; Liu, Y.; Lefevre, C.; Greneche, J.-M.; Toumi, M.; Mhiri, T.; Begin-Colin, S., The Journal of Physical Chemistry C, (2014) 118, 3795. [4] Toulemon, D.; Pichon, B. P.; Cattoen, X.; Man, M. W.; Begin-Colin, S., Chem Commun (Camb), (2011) 47, 11954. [5] Pichon, B. P.; Barbillon, G.; Marie, P.; Pauly, M.; Begin-Colin, S., Nanoscale, (2011) 3, 4696.

Resume : Metallic nanoparticles (NP) embedded in a dielectric matrix have a great potential for technological applications. Synthesis is challenging since one have to avoid NP agglomeration by surfactants, and/or while post thermal treatments to obtain the desired properties into the matrix. Different from standard multistep reduction methods, a totally unexplored way to obtain embedded NPs in thin coatings is Supersonic Cluster Beam Deposition (SCBD),[1] based on condensation of NPs from gas phase atoms. Here we show that SCBD is able to obtain metallic Ag NP embedded into a TiO2 matrix with tunable relative Ag/Ti concentration, coating thickness and Ag NP size.[2] The data show the presence of isolated and polycrystalline Ag NP embedded or partly embedded in an amorphous TiO2 matrix, for room temperature deposition. Emergence of crystalline TiO2 is observed after annealing treatments. Moreover, the TiO2 matrix strongly enhances the adhesion to the substrate with respect to pure Ag coatings. Finally, the coating presents a very good microbicidal activity on Pseudomonas Aeruginosa, a clinically relevant Gram-negative bacterium responsible for life threatening opportunistic infections in high-risk units. These results open a number of possibilities for directly growing the NP-matrix system on desired substrates with tailoring the coating physical properties and the microbicidal spectrum. [1] E. Cavaliere et al., Nanomedicine 2015, 11, 1417 [2] G. Benetti et al. Submitted to APL Materials(2017)

Resume : As, cancer is nowadays the main cause of mortality, it is crucial to design and to quantify an efficient therapeutic approach based on multimodal nanoparticles (NPs). When the metal oxides of inorganic NPs are bombarded with ionizing radiation, very large numbers of electrons are generated, considerably amplifying the lethal dose of energy in a tumor, while the irradiation dose impinging healthy tissues remains low. The higher the atomic number is, the higher the number of generated electrons is. This is the radioenhancement mechanism. A second mechanism called radiosensitizer effect might be involved, which takes advantage of NP toxicity. Once these NPs are internalized in cells, they can stress the cells resulting in ion concentration modification. Therefore, the cells are weakened and are less likely to survive to ionizing radiation. In this context, NPs should be able to cross biological barriers and to be detected in human body, especially in the tumor target, with insertion of rare-earth elements in the metal oxide matrices. Thus, titania and hafnia NPs were synthesized by hydrothermal method with a control of size suitable to take advantage of the passive targeting (enhanced permeability and retention effect). Furthermore, to these metal oxides matrices, rare-earth elements were inserted such as europium, terbium and gadolinium. Thus, the addition could lead to several functionalities such as luminescence tracking, magnetic resonance imaging and nanothermometry.

Resume : Biodegradable zinc oxide nanaoparticles (NPs) became promising material for numerous applications, including biomedicine. We orally administrated fluorescent ZnO NPs doped with Europim (ZnO:Eu) to mice (n=35). After 3h, 24h, 7d, 14d or 1m mice were sacrificed and internal organs were collected for the assessment of biodistribution and localization of NPs in the organism. Along with the measurement of Zn concentration in organs with spectroscopy (AAS). The distribution patterns of ZnO:Eu NPs within tissues were statistically assessed with scanning cytometry, while the extent of biodegradation was semiquantitatively elucidated by confocal microscopy. Results revealed a rapid, efficient uptake and distribution of ZnO:Eu NPs to key organs and tissues, also crossing physiological barriers. Spleen, as well as fat tissue were found to accumulate NPs, and liver was designated for their elimination. An interesting pattern of biodistribution of NPs in the brain was also observed. The peek of NPs transfer to the brain took place 24h post oral administration (IG) with majority of NPs allocated in the areas of dense neuronal networks, limbic system and cerebellum. During following days we observed a drop of NPs-related fluorescence in the examined organs. This work was partially supported by the National Science Center Decision Nos. DEC-2012/05/E/NZ4/02994, 20/0139/N/ST3/04189 (SGGW) and DEC-2012/06/A/ST7/00398 IFPAN.

Resume : Nanomaterials and specifically nanocomposite thin layers became important components in bioanalytical devices since they clearly enhance the performances in terms of sensitivity and detection limits down to single molecules. In this work we exploit the multifunctionality of silver nanoparticles (AgNPs) as plasmonic antenna when embedded close to the free surface of thin silica layers and their strong toxicity towards microorganisms, in particular the photosynthesis of green algae Chlamydomonas reinhardtii. Two approaches were used to elaborate the nanocomposite structures: (i) low energy ion beam synthesis using an implanter modified to work at low energies; (ii) combined sputtering and plasma polymerization using an axially asymmetric RF discharge. Both techniques allow fabricating a single layer of AgNPs embedded in SiO2 films at controlled nanometric distances from the free surface. Structural and optical properties of these nanocomposite structures were studied by Transmission Electron Microscopy (TEM) and by ellipsometry or optical reflectance spectroscopy, respectively. The short-term toxicity of embedded AgNPs to photosynthesis of Chlamydomonas reinhardtii was exploited using fluorometry to determine the bio-available silver release. The “spectro-inside” concept which consists of using AgNPs themselves as probes for amplifying and detecting optical signals of bio-objects (molecules) located in their vicinity was further confirmed.

Resume : Quantification of biochemical processes is of extreme importance in fields such as Biology or Medicine. However, the integrability of sensor materials with the silicon chip technology is still a challenging issue. This, together with the lack of sensitive, fast, cost-effective and miniaturized sensor devices suggests that Transparent Conductive Oxides (TCOs) may be suitable for developing high quality biosensors. In this respect, nanostructured indium tin oxide (ITO) films present an interesting combination of properties: good electrical conductivity and optical transmittance, together with a high surface-to-volume ratio, the latter implying enhanced sensitivity. A study of the viability of nanostructured ITO-based biosensors is presented. For this purpose, nanostructured ITO was deposited onto silicon substrates by electron beam evaporation. Thin ITO films were used as a reference. Raw electrodes were characterized morphologically by atomic force microscopy (AFM), and sheet resistance was measured in a four points probe station, obtaining commercial-like values (≈ 10 Ohm/sq). Electrodes were derivatized with 3-(glycidoxypropyl)trimethoxysilane, and a well-known enzyme-linked immunosorbent assay involving horseradish peroxidase (HRP) was performed. Immobilization of the protein was confirmed by FTIR spectroscopy. Amperometry was used to test the biosensor performance, and results confirmed a much better outcome for nanostructured ITO-based biosensors compared to thin ITO films.

Resume : Nowadays silver nanoparticles (AgNPs) are gaining considerable interest owing to their potential application in biological systems as antimicrobial agents or as candidates for biosensors and bioelectronics. Since in all such applications the AgNPs are in direct or indirect contact with proteins and biomolecules, a comprehensive study of such interactions is mandatory. In this work, we coupled AgNPs, known to be well tolerated by mammalian cells, and discosoma red fluorescent proteins (DsRed) that displays exceptional photo-stability. AgNPs single layers were deposited on SiO2/Si and on quartz substrates by sputtering and covered by a thin SiO2 plasma layer by plasma polymerization. The structural and optical properties of the nanocomposite substrates were characterized by TEM analyses and optical spectroscopy. Small volume sessile droplets of different DsRed diluted solutions were then deposited on the surface of the nanocomposites. The protein layer thickness is controlled at the nanoscale level. The optical properties (photoluminescence, refractive index and absorption) of the dehydrated DsRed layers have been studied, suggesting that the DsRed proteins preserve their natural state after absorption on the nanocomposite surface, in accordance with FTIR analyses. Moreover, the Raman spectrum of DsRed thin layers, not visible in absence of AgNPs, has been observed owing to SERS effect, making these Ag nanocomposite substrates good candidates for biosensing applications.

Resume : Metal and, in particular, gold nanoparticle (Au NPs) have attracted great interest due to their unique physical and chemical properties: they can be easily synthetized in different media with a good control over size and distribution. Moreover Au NPs can be covalently functionalized with thiolated molecules to add new functionalities and to make stable organic/inorganic hybrids that can be used for a wide range of applications. Among them, one of the most promising is the development of sensors, specific for different analytes, depending on the chosen ligand. In this work we report on a new scaffold based on 3D networks of Au NPs, interconnected and cross-linked by electrical insulating oligo-ethylene glycol dithiols (SH-OEG-SH) as electrical resistive humidity sensor. The use of SH-OEG-SH gives great control over the inter-particle distance ensuring the charge transport by tunnelling and a good flexibility of the system that undergoes swelling upon absorption of very small amounts of water molecules from the atmosphere. Upon absorption of water, the increased distance between the particles can dramatically drop the tunnelling current measured through the network, making the device extremely sensitive over a wide range of condition: from ppm to 100% of relative humidity. Moreover these devices can be made on any kind of substrate and, being covalently attached to the measurement electrodes, they show full reversibility, great stability over time and can be washed and immersed in water without any damage.

Resume : For Silicon solar cell, increasing its efficiency with the aim of always keeping a low cost process is one of the goals of the Si PV industry to continuously decrease the cost of the power generation. This is the condition to remain a major player in the provision of power solutions in the forthcoming years. Among the different loss paths known in a Si-SC, the thermalization effect as well as the transparency of the cell due to the mismatch between the solar spectrum energy range (UV and IR regions) and the cell band gap energy can be overcome. To achieve such a goal, frequency conversion layers so-called Down-Conversion (DC) or Down-Shifting (DS) or Up-Conversion (UC) layers have been developed in order to convert one UV incident photon into two IR ones (DC), one UV incident photon into one visible one (DS) or two IR photons in one visible one (UC) that can be absorbed by the Si cell. This paper aims at proposing solutions compatible with the Si-PV industry allowing an efficient absorption of the solar spectrum. Rare earth doped layers have been fabricated by either sputtering or ALD techniques. The use of metallic Nps has been developed to increase the optical path length of pumping photons and thus improving the efficiency of the system. EQE measurements and electrical and optical characteristics have been carried out on industrial Si-SC and will be presented. This work has been supported by the ANR (GENESE- ANR-13-BS09-0020-01), ORCHID PHC and the QNRF, Grant 8-1467-1-268.

Resume : Perovskite solar cells have demonstrated potential for a promising alternative to conventional silicon solar cells as they require lower fabrication costs and have reported power conversion efficiencies exceeding 20%. An approach to further boost efficiency consists in embedding plasmonic concentrators in the metal contacts with the aim of enhancing the active layer’s absorption properties. In particular we have utilized a conventional structure with a top corrugated metal contact to support the generation of surface plasmon polaritons when illuminated as well as an inverted structure where nanodisks on the light incident contact act as subwavelength scattering elements. In both cases the attained change of light propagation direction leads to the enhancement of the thin film’s absorbance which in turn results in an increased open circuit voltage and thus a higher efficiency compared to a cell comprising the same thickness but without plasmonic-induced absorption enhancement. The plasmonic concentrators are fabricated via nanoimprint lithography directly on the hole conducting layer or the glass substrate so as to define a hexagonal periodical pattern of nanoholes in the respective polymer using molds comprising nanopillar arrays with pitch ranging 200 – 350 nm and diameters ranging 100 – 200 nm on 1 cm2 silicon substrates. Plasmonic concentrators exhibiting enhanced optical performance represent a promising way of boosting perovskite solar cell efficiencies.

Resume : More frequently high refractive index dielectric matrix are used in thin film photovoltaics as transporting layers with good optical proprieties. Doping such matrix with plasmonic resonant scatterers is a promising way to further increase energy conversion efficiencies by trapping incoming light in ultrathin solar cells. Colloidal plasmonic oligomers are obtained following a cost-effective selfassembly strategy and incorporated in organic based cells produced using spincoating techniques in ambient air conditions. An interesting increase is observed of both external quantum efficiency (EQE) and short-circuit current for solar cells loaded with plasmonic oligomers compared with reference organic cells.Theoretical calculations demonstrate that the wavelength dependent EQE enhancement is a resonant process due to the increased scattering efficiency in plasmonic antennas allowed by a chemically controlled 1 nm nanogap. The nanogap antennas are linked at a controlled distance of a few nanometers by Dithiothreitol molecules. The spacing molecules ensure a minimum distance that plays a fundamental role in the formation of intensity hot spots in the nanogap as well as large and redshifted scattering peaks. This OPV device, realized in ambient air condition, exhibited an efficiency 14% higher than the reference one showing a relevant enhancement in the red part of the EQE measurements. Francesco Pastorelli, Sebastien Bidault, Jordi Martorell, Nicolas Bonod, DOI:10.1002/adom.201300363

Resume : Plasmonic solar cells (PSCs) have been explored as a route for improving charge carrier generation of photovoltaic devices, with localized electromagnetic field enhancement around metal nanoparticles as a proposed mechanism. However, there is often a concern about exciton quenching and charge recombination. To suppress such issues, these metal nanoparticles are coated with a thin dielectric shell. We investigated the optical behavior of the integration of gold-silica core-shell nanospheres (Au@SiO 2 NSs) with different shell thicknesses into a ~ 30 nm-thick of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer which is used as a traditional buffer layer in organic solar cells. The morphology and size of the chemically synthesized Au@SiO 2 NSs were determined by TEM, indicating that the average diameter of the Au core is about 50 nm, while the thickness of dielectric SiO 2 shell can be adjusted around approximately 5 nm or 10 nm. The effect of Au@SiO 2 NSs on the surrounding electromagnetic field in such heterogeneous matrix and subsequent PSCs was examined using numerical simulation based on a 3D-FDTD method. Furthermore, a broadband absorption enhancement in the concerned films which can be primarily attributed to the coupling of the strong localized surface plasmon resonance around 530 nm wavelength peak is observed by UV–Vis absorption measurement.

Resume : Metal nanoparticles (M-NPs) are suitable to be integrated in silicon based solar cells due to their unique optical and electrical properties which are very different from those of bulk material. Illuminated by light, M-NPs can exhibit localized surface plasmon resonance (LSPR) caused by the collective oscillations of the conduction electrons. This behavior results in a strong optical scattering by multiple and high angle scattering or a strongly enhanced optical near field in the close vicinity of nanoparticles depending on their position (on top surface of silicon or embedded in a dielectric medium). Different factors can influence the characteristic of the LSPR (the frequency, the width and the intensity of the resonance), such as material type, NPs size and surrounding medium. Tuning the LSPR characteristics can lead to interesting properties in terms of enhancement, localization and guiding of the electromagnetic field on sub-wavelength scales. In this contribution, we attempt to investigate the effect of these factors on the optical behavior induced by metallic NPs. We use analytical simulations based on Mie theory which dictates the expressions of extinction, scattering and absorption cross section of illuminated NPs. Mie theory is valid for any size of NPs and successfully predicts the existence of multiple resonance excitation. It is revealed that particles of certain size, type and embedded in a medium with a high refractive index enable a strong scattering of light which can be useful in solar cells application.

Resume : Strong confined structures, such as the Quantum Dots (QDs), were used as promising nanostructures to develop the third generation of photovoltaic solar cells due to their size dependent energy band gap and the increased optical absorption. These devices are composed by a large array of embedded QDs in an insulator matrix as a top structure of a classical p-n junction creating a tandem solar cell. Within this structure, two different optical absorption energy edges are obtained increasing the efficiency of the cell. However, the efficient extraction of the photogenerated carriers in the QD matrix imposes new technological and material requirements. Besides, an electron transport capable to deal with these large QDs arrays is also necessary. Here, we present an electronic transport model based on Transfer Hamiltonian Formalism and rate equations to describe the ballistic charge transport in QDs embedded in an insulator matrix. This methodology was compared to NEGFF reproducing the same theoretical trends1 and it also demonstrated that can be easily scalable for large systems2. Two unique features of this transport model are: (i) the model is based on just a few basic material parameters and on the device geometry; (ii) it is simple enough to tackle problems involving large number of Qd, which is the case of real devices. Moreover, it is compatible with ab initio theories taking advantage of the atomistic calculations in order to accurately describe the Qd electrical properties as we have demonstrated in Ref 3. Once the electronic transport model was presented and validated, the light interaction was also included making possible to describe and simulate optoelectronic QD based devices. Thus, a complete and valuable theoretical tool based on low-level material and geometrical parameters are developed which can be used to design and predict the optoelectronic response of these devices. 1 S. Illera, N. Garcia-Castello, J. D. Prades and A. Cirera, J. Appl. Phys 112, 093701 (2012). 2 S. Illera, J. D. Prades and A. Cirera, J. Appl. Phys. 117, 174307 (2015). 3 N. Garcia-Castello, S. Illera, R. Guerra, J. D. Prades, S. Ossicini and A. Cirera, Phys. Rev B 88, 075322 (2013).

Resume : Noble metals nanocrystals with high index facets have drawn much attention because of their enhanced catalytic peformance. This study reported that a sensitive amperometric sensor based on polyhedral Au nanparticles (PANs) using for the rapid and accurate detection of NADH by electrochemical reactions. PANs enclosed high index facets provided a significantly high sensitivity as well as detected NADH with a lower detection limit of 0.05 mM. The values of sensitivity for the disposable electrochemical sensors to NADH was calculated to be 0.74 μA/mMcm2 at the working potentials of 0.2 V. In particular, the extremely small loading amount of PANs (7.81×10-5 g/cm2) shows unusually high sensing performance for the electrochemical reactions NADH. Our discovery of the reaction mechanism inPANs provides new understandings of the interaction between Au modified and disposable electrochemical sensors, and gives new way to control the interaction between gold and the support as well as electrocatalytic activities.

Resume : DC arc discharge in deionized water was used to synthesize ZnO colloidal nanoparticles. Arc discharge in liquid is a cost effective method for quick mass production of nano-structured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposite produced by interaction of different active species in high-pressure and high-temperature plasma at solid-liquid interface. Different sized nanoparticles were fabricated with diameters of 29, 37, 42 and 63 nm at applied discharge currents of 150, 100, 50 and 20 A respectively without any chemical additives. Optical emission spectroscopy was used to determine the plasma elemental composition and parameters. Scanning electron microscopy, X-ray diffraction and UV-visible spectroscopy, were employed for characterization of particles size, shape, crystal structure and optical properties respectively. In addition the oxidation mechanism of as prepared nanoparticles was investigated based on optical emission spectroscopy. The results provide a simple and flexible method for synthesis of Zn/ZnO nanoparticles with adjusting metal/metal-oxide ratio composition.

Resume : Metal nano aggregates embedded in glass can exhibit interesting properties for decoration, photonic, sensoring, and so on… Among lot of preparation methods leading to the incorporation and growth of metal nanoparticles in glass, we have chosen the well used technics based on ion exchange in the case of silver or by the direct inclusion of metal (in the oxide form) in the initial glass composition. Growth of highly concentrated nanoparticles is then possible by ns or femtosecond laser irradiation in the case of ionic exchange samples due to the high silver concentration near the glass surface or by laser induced defect and further annealing in the case of metal composite glass. Generation of defects inside the glass and growth of silver nanoparticles is further evidenced by UV-Visible measurements and scanning of the surface plasmon resonance according to the deposited laser energy. The surface plasmon resonance is modelised by drude or mie models based on bulk data. Glass laser interactions are observed by SEM observations or by numeric observations according to the laser deposited power, scanning speed and recovering rate in order, among other, to determine a thermal (Ablation?) or non thermal process. Moreover, we developed a method to achieve glass reversible modification, using laser processing and thermal annealing with appropriate parameters. Femtosecond laser irradiation on glass generates glass coloring and thermal annealing lead to erasing the previous colored area.

Resume : As an alternative for DRAM, a new memory named as resistance switching random access memory (RRAM) has been highly examined, and several studies to impart flexibility to RRAM have been reported, like as to use a flexible polymer which possesses resistance switching capability. However, the reported results using resistance switchable polymers usually exhibited severe problems such as rather poor performance and complex molecular structure requiring highly complicated synthesis and extremely low yield. To suggest promising alternative to realize flexible RRAM, a resistance switchable polymer nanocomposite has been prepared employing one-dimensional nanofillers which are composed of two components; the one is permanently conductive core providing facile electron transport, and the other is a skin layer to gate electron flow delivered through the conductive core. When embedded in dielectric polymer matrix, fillers of one-dimensional shape above percolation limit tend to form a highly connected network-like structure which can contribute as deformable pathways for electron transfer. As a result, the polymer nanocomposite by mixing of the resistance switchable one-dimensional nanofillers with dielectric polymer matrix successfully exhibited a resistance switching behaviour of high reliability and On/Off ratio, along with flexibility due to the presence of nanowire networks. The advantages of our approach include simple and low cost fabrication procedure along with sustainable performances suitable to resistance switching memory application.

Resume : We evaluate the advantage of this genipin (Gp)-crosslinked CHI hydrogel to be used as carrier for local antibacterial nanomedicine in treatment of infection-combined wound. Infection has been the first cause for death of clinical burn and trauma patients. It is very important for a prompt control against infection. Silver sulfadiazine (AgSD) shows inhibition effect against both G+ and G- bacterium and ability to enhance wound convergence, therefore it had been used as the first line drug in antibacterial treatment of local wound. However, the therapeutic effect of AgSD has been limited by its poor solubility and cytotoxicity, which two problems have not been completely solved so far. To overcome the two problems we comminuted the AgSD powder into nanocrystal (NCT) particles, and hope the resultant huge surface area could improve the dissolution behavior as well as the antibacterial effect through the increased interaction between drug and bacterium. However, just like other antibacterial nanomedicine, AgSD/NCT easily tends to grow and aggregate due to its huge Gibbs surface energy, which make it loss its advantage obtained from nanosization. When the AgSD/NCT was immobilized into CHI hydrogels its physical stability could be improved meanwhile its antibacterial ability could be retained and its cytotoxicity against fibroblasts, epithelial cells and keratinocytes could be reducted. Gp-crosslinked CHI hydrogel not only can accelerate cellular proliferation and spreading, but can be an ideal carrier for local nano-antibacterial medicines. It is a very promising material to be used for treatment of wound combined with infection. Keywords: Chitosan; Genipin; Hydrogel; Nanocrystal; Silver Sulfadiazine; Wound healing.

Resume : Piezoelectric nanogenerator based on oriented assembly of nanowires is a dominant device developed for converting mechanical energy into electrical energy. By finite element method, the nanogenerator based on lead zirconate titanate (PZT) nanowires is modeled to evaluate its capacitance, charge density on the top electrode and open circuit output voltage. The investigation on size-dependent performance demonstrates that the output voltage of the device increases with the increase of the length as well as the decrease of the diameter. The output performance depends on the types of PZT materials. When adopting PZT-7A as the piezoelectric materials, the nanogenerator could obtain a larger output. In addition, our investigation also shows that the device?s thickness affects slightly the output voltage. Compared with PMMA, PDMS could give rise to higher output voltage. Based on different types of PZT materials and polymers, our study presents the output voltage of the nanogenerator by changing of the PZT nanowire?s length, diameter, and the nanogenerator?s thickness. These results will be of crucial importance for optimal of the performance of the flexible nanogenerator based on oriented nanowire assembly.

Resume : Electromagnetic parameters of individual carbon nanotubes (CNT) have been under intensive investigation for the past two decades. Due to a high aspect ratio and high conductivity, the CNTs are actively used as inclusions in the dielectric matrix to fabricate materials for effective electromagnetic shielding applications. However, fabrication procedure, as a rule, includes an ultrasonic treatment resulting in the partial cutting of the CNTs. Moreover, the electrostatic interaction of the carbon nanotubes leads to their partial aggregation during fabrication processes. The aggregation effect increases as the concentration of CNTs increases. Let us also note that interaction of the electromagnetic wave with aggregated CNTs is weaker than with the same amount of individual tubes. That is why the aggregation effect worsens the electromagnetic parameters of CNT materials. The static electric conductivity of the composite material can be one of the criteria to estimate the quality of CNT-based composite fabricated. The higher conductivity, the more homogeneous is a distribution of the inclusions in the dielectric matrix. However, the maximal value of the static conductivity corresponding to the homogeneous distribution of the inclusions is usually unknown. Here we report an effective method to estimate a quality of CNT-based composite prepared. The method is based on the application of the microwave and terahertz spectroscopies.

Resume : Surface-enhanced Raman spectroscopy (SERS) is universal method for analysis of small quantities of organic analytes with high sensitivity [1]. It is a multiple times enhancement of the Raman signal from the analyte molecules located on a substrate, comprising individual nanoparticles or nanostructured films of noble metals. As a result of laser irradiation on the metal surface plasmons generated by increasing the electric field around the metal, which increases the Raman signal intensity up to 1011 times. It is remarkable that different analytes absorb (and fluoresce) at different wavelengths, and so lasers of different energies should be used. Therefore, an urgent task is to form a substrate for SERS spectroscopy which has multiband plasmon resonance in a wide energy range. In this project, gold inverse opals with wholly or partly hexagonally ordered pores are proposed as SERS-active substrates. The aim of this work is the formation of gold inverse opals using different electrolytes, study of the correlation of optical properties of the films with their morphology peculiarities, as well as the use of obtained samples as SERS-active substrates. Synthesis of inverse opals consists of several stages: obtaining polystyrene microspheres, formation of colloidal crystals, electrocrystallization of gold in pores of matrix, and its subsequent removal [2]. The quality of the samples at each step influences the final structure of the porous gold film. Au inverse opals were prepared by electrochemical deposition of gold from chloride, citrate or sulfite electrolytes into ordered matrices consisting of microspheres with diameter D = 400 and 530 nm, as well as into disordered matrices consisting of microspheres with D = 200, 300, 500 and 600 nm. (with standard deviation less than 5%). It should be added that the electrolyte composition may affect on particles size, and hence, on plasmon resonance bands. In current project optimal parameters for ordered colloidal crystals formation are found (temperature, concentration of suspension, electric field intensity). Based on them, Au inverse opals are obtained with various normalized thicknesses in the range 0.05 ÷ 1.1 of microsphere diameter in the matrix. For electrodeposition of Au, optimal conditions are found: chloride electrolyte, deposition in potentiostatic mode at Ed = 0.8 V versus Ag / AgCl reference electrode. Measuring of reflection spectra was performed by varying incidence angles and azimuthal angles. On reflection spectra of the samples a number of various plasmon resonance features are observed. Resonances are associated with the presence of local plasmons of individual particles, Mie and Bragg plasmons in a mixed state [3]. The condition of Mie and Bragg plasmon excitation is determined only by surface morphology depending on period and thickness of porous gold films. Intense local plasmon resonance is typical for all gold films of different crystallinity and its profile depends on grain size varied in the range of 20-50 nm and through this on reflectivity characteristic in 400-1000 nm range. Using XPS method surface composition of the gold films was analyzed to reveal presence of adatoms which could result from different electrolyte compositions. The Raman data, obtained on substrates, show an increased intensity of the Raman signal from fluorescent dyes rhodamine 6G and methylene blue at concentrations up to 10-10 M (volume of aliquot ~ 1 mkl) by their excitation with green (λ = 514 nm) and red (λ = 633 nm) lasers, respectively. The spectra obtained from different parts of the substrates are identical, suggesting about the reproducibility of samples and surface uniformity of substrates. The enhancement factor in the case of methylene blue is G = 106 for most of the concentrations of aliquote. After washing substrates with distilled water, microstructure of the substrates reveals no changes, and SERS effect is observed, that demonstrates the SERS-active substrate to be renewable. Acknowledgments Authors wish to acknowledge their colleagues, namely, Dr. K.S. Napolskii, Dr. N.A. Sapoletova, Dr. Vassiliev S.Y. for their assistance with experiments and fruitful discussion of experimental results. Authors gratefully acknowledge the support of the Russian Foundation of Basic Research under grant No 15-33-70050-mol_a_mos. References [1] Semenova A A, Goodilin E A, Brazhe N A, Ivanov V K, Baranchikov A E, Lebedev V A, Goldt A E, Sosnovtseva O V, Savilov S V, Egorov A V, Brazhe A R, Parshina E Y, Luneva O G, Maksimov G V, Tretyakov Y D. 2012 J. Mater. Chem. 22 24530 [2] Sapoletova N A, Martynova N A. Napolskii K S, Eliseev A A, Lukashin A V, Kolesnik I V, Petukhov D I, Kushnir S E, Vassilieva A V, Grigoriev S V, Grigoryeva N A, Mistonov A A, Byelov D V, Tretyakov Y D. 2011 Physics of the solid state 53 (6) 1126-1130 [3] Kelf T A, Sugawara Y, Cole R M, Baumberg J J, Abdelsalam M E, Cintra S, Mahajan S, Russell A E, Bartlett P N. 2006 Phys. Rev. B 74 (24) 245415

Resume : Most of the nanomaterials are easy to leak from the electrode surface，which makes the measured electrochemical signal unstable，thus reducing the performance of the sensor．Glucose biosensor constructed by nanomaterials with good performance can not only overcome the problem of leakage of nanomaterials，but also achieve direct electron transfer between the redox．Active center of the enzyme and the electrode surface，thus improved the response time and the sensitivity. Therefore, the Chitosan/Prussian blue/graphene nanocomposite (CS-PB-GR) was synthesized based on the electroactive species including Prussian blue, graphene and chitosan． The CS-PB-GR nanocomposites, nano-Au and half sword bean globulina (Con A) were applied to construct the GOD／Con A／GOD／nano-Au／CS-PB-GR／glassy carbon electrode．The nano-Au and Con A effectively improved the amount of glucose oxidation．A pseudobienzymatic system was formed with PB nanopartieles and GOD to enhance the esponse signal．The electron transfer rate between the activity center (FAD) of enzyme and electrode surface was significantly accelerated by the application of grapheme and PB nanoparticle．The biosensor exhibits good electrocatalytic behavior towards detection of glucose with fast response，high sensitivity and selectivity and realized the direct electron transfer．

Resume : The early detection of pathogenic or lethal viruses can effectively reduce the death rate and spreading of diseases. Therefore, we propose a hybrid upconversion nanoprobe/nanoporous alumina membrane system for ultrasensitive detection of viruses. The system presented a limit of detection (LOD) at about 300 fM and tested by using clinical sample of influenza virus. The detection scheme is based on the luminescence resonance energy transfer between upconversion nanoparticles and gold nanoparticles on nanoporous alumina membrane. The upconversion luminescence (UCL) is triggered by near infrared (NIR) excitation, which does not pose photodamage to the biological sample and induce background fluorescence. The hybridization time for the biosensor is around 2 hours. Moreover, the sensor is specific to the target virus oligonucleotide (oligo). As a result, the sensor is rapid, simple and specific. Since the recognition is achieved by the probe sequence, the sensor can be adapted to other types of virus detection by simply modifying the probe sequence.The system can be generalized as an versatile platform for viruses detection.

Resume : Bimetallic Pd-Pt nanoparticles (NPs) find important devices applications for sensing detection, catalysis, direct alcohol fuel cells, hydrogen storage, etc. However, the success of such technologies is subjected to the development of simple, versatile, low-cost, high-throughput methods for the controlled production of the Pd-Pt NPs. In addition, the physico-chemical response of the Pd-Pt NPs can be largely tuned by controlling their size and composition, so that the fabrication methods should allow such a fine control. Finally, for solid-state device applications, such methods should allow the production of NPs directly on solid surfaces. The preparation of Pd-Pt NPs has been achieved by some methods such as solvent extraction reduction, alcohol reduction, and impregnation–reduction which do not fulfill completely these requirements. So, we present an original method for the controlled production of bimetallic Pd-Pt NPs directly on fluorine-doped tin oxide (FTO) by a laser-based self-organization strategy. The following procedure was developed: we deposited thin Pd/Pt bilayers on FTO substrate with thickness xPd and xPt of the Pd and Pt layers; we induced the alloying and dewetting processes of the bilayers by laser irradiations of the bilayers. These processes result in the formation of PdxPty alloy NPs being x and y tunable by xPd and xPt. The analysis of the NPs size, surface density and composition versus the laser fluence and xPd and xPt are presented and discussed.

Resume : For the ease of processing flexible electronics, 3D printing technology must be developed in order to reduce the process time and cost. There are many different printing methods available depending on the ink property. In this study, the elastomer based dielectric ink was prepared with the introduction of high dielectric inorganic filler. Of many printing methods, this specific paste targets the non-contact direct patterning, namely, the drop-on-demand (DoD) inkjet printing technique. To optimize the ink printability, the dispersion of inorganic filler was enhanced by surface modification which also resulted in a lower dielectric loss. The rheological properties were measured to observe the storage modulus (G’) and the loss modulus (G’’). Also, the dielectric properties were measured by fabricating a thin film by casting method. The paste with different filler loadings and solid contents were formulated and investigated to select the most suitable ink paste.

Resume : Copper- or manganese-doped zinc sulfide nanostructure arrays draw close attention due to their great promises in development of modern optoelectronic devices including light sources, optical touch panels or fluorescent labels. The work is focused on development of cheap pathways for formation of ordered ZnS:Cu(Mn) nanosized dot arrays formed by condensation of thermally evaporated ZnS and Cu2S powders in the pores of highly-ordered anodic alumina matrix in ultrahigh vacuum. Matrices with pore diameters of 40, 60 and 120 nm and thickness of interpore walls of 15 ( -5) nm were formed in aluminum plate and glass substrates. ZnS:Cu(Mn)@AAO composites were study by SEM, EDX, XPS, UV-VIS spectroscopy, X-Ray Diffraction and EXAFS-spectroscopy methods in comparison with ZnS:Cu(Mn) thin films. SEM studies shown that the form and arrangement of semiconductor nanostructures replicates well the form and arrangement of matrix channels. EDX analysis shown the penetration of deposited materials into pores to a depth of 3 micron. Luminescent and electroluminescent properties have been also investigated. The samples exhibit luminescence in a visible region depending on type and concentration of dopant atom and pore size of matrix. The work is supported by Russian Scientific Foundation (Grant № 15-19-10002) and Russian Foundation of Basic Researches (Grant № 16-48-180303).

Resume : Metal nanoparticles have a wide variety of applications due to their novel properties including localized surface plasmon resonance (LSPR) [1,2]. Thin film dewetting is an attractive method to fabricate these metal nanoparticles because it can directly transform a thin film to nanoparticles in a very short time. A previous work has shown that Ag thin films can be dewetted into nanoparticles without oxidation by a single laser pulse [3]. Although both Ag and Au exhibit superior plasmonic properties, they alone have a limited tuning range of LSPR absorption peak. In contrast, bimetallic nanoparticles can provide a wider and more flexible range of LSPR absorption. In this work, Ag/Au bimetal nanoparticles were fabricated from an Ag/Au bilayer thin film (thickness = ~10 nm) using a Nd:YAG nanosecond pulse laser at  = 1064 nm and E=55 mJ to achieve more flexible tuning of LSPR wavelength. Various color spectra of dewetted Ag/Au thin films were obtained by modulating the thickness ratio of the bilayer film, as shown in Fig. 1(a). Elemental analysis performed by energy dispersive X-ray spectroscopy showed that Ag/Au nanoparticles fabricated by laser-induced dewetting were in complete solid-solution states. The LSPR absorption peak was gradually red-shifted as the relative ratio of Au layer increased (Fig. 1(b)). We were able to tune the peak position from 430 nm to 525 nm by controlling the thickness ratio.

Resume : In this study, we developed a fluidic photonic crystal reflective display. The photonic crystal structure was formed with anionically charged acrylic colloidal polymer dispersed in non-aqueous medium. In the solution, colloidal polymers are self-assembled to face centered cubic structure due to electrostatic repulsive interaction between particles. With low DC voltage, the colloidal lattice spacing was changed and the diffracted color was also changed by Bragg’s law. Such electrical tunning of color could be utilized as a full color display device. By using the oil with low dielectric constant, no electrochemical reactions occurred which are inevitable problems in water system. To overcome the aggregation of particles in oil, the surface charge of colloidal system was controlled by using a specific surfactant.

Resume : Manufacturing of optoelectronic devices that require converting light emitted from a blue GaN chip in white light is based on hybrid materials like phosphor - polymer type. Although there are numerous studies in the field of white light conversion, the biggest problem is still the integration of the phosphors into the polymer matrix in order to deposit on the chip. In this work we report obtaining a YAG:Ce phosphor, the surface functionalization of and its embedding in a PMMA matrix. The YAG:Ce was obtained by coprecipitation method and sintered at 1200°C. For a better dispersion and a good compatibility with polymeric matrix, the YAG:Ce were modified with elaidic acid. The FTIR spectrometry was used to study the chemical configuration of the YAG:Ce and the functionalised phosphor before and after incorporation into the polymeric matrix. FTIR spectra demonstrate the phosphor transition from amorphous to the crystalline phase and the formation of M-O. In the case of the modified phosphor, the hydrocarbon chain around the YAG:Ce forming a "closed-packed"- like crystalline state, was observed. Also, the spectra confirm the presence of luminescent material in the PMMA matrix. The luminescent properties of the nanoparticles and hybrid materials were studied by fluorescence spectroscopy. Comparing the emission spectra for YAG:Ce and YAG:Ce-PMMA,we observed a small shift in wavelength that may be attributed to the changing space around the YAG:Ce nanoparticles in the hybrid material, and to the reabsorption of the emitted light by neighboring chains or to the intermolecular forces. The phosphor luminescent properties improvement indicated the YAG:Ce-PMMA as a useful hybried material for optoelectronic applications such as white LEDs.

Resume : We model the light/Ag nanoparticles (Ag NPs) interaction in SiNx host matrix, investigating size and spatial distribution effects on the VIS-NIR spectral range. In SiNx-Ag NPs matrix, we model the Ytterbium/Terbium rare earth (RE) ions optical excitation investigating the RE concentration effect under solar optical pumping condition and seeking for the optimal layer with the highest quantum efficiency of Down Conversion (DC). Following the DC layer optimization we proceed at the integration on n+- p junctions. We therefore realized planar n+- p junctions using (180 keV, 10E18 cm-3) implantation of phosphorous in 2x10E15) cm-3 boron p type silicon material. Before the deposition of the Ag NPs or the SiNx layer, a thin 1.5 nm Al2O3 layer passivation is deposited using ALD technique, as a tunneling passivation layer all over the structure. Structures including a SiNx layer (80 nm) with or without Ag Nps or Down Conversion Tb3+-Yb3+ co-doped SiNx layers with or without Ag NPs are realized. The diffusion effect of the light by the Ag NPs into the active layer of the device is first evidenced with the SiNx layer. (electric yield varying from 1.4 to 7 %). Finally, the same behavior is observed with the Down Conversion Tb3+-Yb3+ co-doped SiNx layers. Acknowledgments: This work was partly supported the “GENESE” contract (13-BS09-0020-03) from the Agence Nationale de la Recherche, ANR. T. Xu acknowledges support from the National Natural Science Foundation of China (61204014).

Resume : Electron or ion irradiation of solids normally causes formation of atomic defects in a solid state target and spoils its properties. It may result in irradiation-induced amorphization, recrystallization and annealing and may induce changes of electrical properties of solid-state materials and devices. Therefore during the last few decades there was significant activity to explore such alterations in various types of semiconductor devices, in particular in those based on metal-oxide-silicon. Irradiation may also cause formation of amorphous nanosized domains and nanocrystals by decomposition of the target material. Films of SiOx (x=1.3, 200 nm) and composite a-Si-SiOx films, containing amorphous Si nanoparticles (grown by thermal annealing at 700 °C of the SiOx films) are prepared on crystalline Si substrates. A part of the films are irradiated by 20 MeV electrons with two different fluences (7.2E14 and 1.44E15 el/cm2). The film thickness and optical constants (extinction coefficient, refractive index, and absorption coefficient) are determined by spectroscopic ellipsometry. The Bruggeman effective media approximation model is applied for composition evaluation and to specify the influence of the nanoparticles content on the optical properties of the films. It is shown that the SiOx films are optically homogeneous. The electron irradiation does not change significantly the film composition but at the fluence of 7.2E14 el/cm2 it leads to small changes in the optical constants and the band gap which imply formation of amorphous silicon nanoclusters homogeneously distributed in the oxide matrix. The electron irradiation of the a-Si-SiOx composite films leads to a significant red shift of the SiOx matrix’ optical band gap thus suggesting an increase of the already existing amount of a-Si nanoparticles. The increase shows that further phase separation occurs in the oxide matrix which is induced by the electron irradiation. The results obtained for both types of layers indicate that the effect of electron irradiation is similar to that of the thermal treatment at 700 °C.

Resume : Due to the unique structural properties of two-dimensional (2D) materials, including graphene and transition metal dichalcogenides (TMDCs), it is difficult to form an ultra-thin and conformal insulating film on them using an atomic layer deposition (ALD) process. Hence, several surface functionalization methods, such as a plasma treatment or an introduction of seed layer, have been widely studied [1, 2]. Among various 2D TMDCs, MoS2 is considered to be one of the promising channel materials for field-effect transistors (FETs). In this work, an ultra-thin Hf film (easily oxidized to HfO2 during the subsequent ALD process) was deposited on the MoS2 flakes using an e-beam evaporator, followed by an ALD-HfO2 process to produce a totally ~5-nm-thick HfO2 film without damage. The structural integrity of the Hf-seeded dielectric films was examined using scanning electron microscopy, transmission electron microscopy, and conductive atomic force microscopy. In addition, top-gated MoS2 FETs were fabricated and characterized to further demonstrate their electrical integrity. [1] W. Yang et al, Sci. Rep., 5, 11921 (2015) [2] S.-J. Jeong et al, Sci. Rep., 6, 20907 (2016).

Resume : For strain and pressure sensors, piezoresistive thin films with their high sensitivity are a material class of interest. In this work, metal-ceramic composite thin films are investigated. Cosputtering platinum and different insulating ceramics with a low metal content and high substrate temperature results in a ceramic phase with embedded metallic nanoparticles. We investigated resistivity and its temperature coefficient (TCR), piezoresistivity (longitudinal and transverse gauge factors kL and kT), and the structure of the films by XRD and TEM. For platinum/aluminum-oxide films, sheet resistances of several Megaohm per square were found, with TCR between -5000 ppm/K and 0. Longitudinal gauge factors were up to 10 with a transverse sensitivity ratio q=kT/kL of typically 0.7. The films are stable up to at least 450 °C. For platinum/boron-nitride films, resistances and TCR are similar. They are less stable, but their kL reach values of up to 25 with q around 0.7. Literature on granular metals describes electron tunneling between individual particles. To understand a film of many particles, we build models of large particle networks. Resistivity and gauge factors are found using Monte Carlo simulations of the networks with variation of, e.g., particle size. Several parameters such as metal content and particle size are investigated; results are visualized using current densities in the network. It is found that disorder in the particle arrangement leads to transverse sensitivity.

Resume : During last decades the researchers have focused on semiconductor nanoparticles (NPs) for their excellent performance and variable color of emission which are attractive for applications in electronics, optoelectronics, biology and medicine. The functionality of NPs can be tailored by controlling surface coverage of NPs, however, the interaction of NPs with their surroundings is yet to be explored. We report the studies of the influence of varied interfacial coverage on the spectroscopic properties of CdS/polymer nanocomposites. The interfacial conditions were tuned by changing either the capping material or surface density of passivating species that surround a NP avoiding new chemical species formation. The surface-dependent properties were analyzed by photoluminescence and optically detected magnetic resonance (ODMR) methods and the nature of paramagnetic centers involved in the emission processes was elucidated. All ODMR signals observed are related to the centers that form the energy levels which are involved into the processes of excited carriers relaxation preceding their radiative recombination.

Resume : The conductive oxide nanoparticles of fluoride (F)-, antimony (Sb)-codoped tin oxide (SnO2) were synthesized by sonochemical-assisted precipitation process using metal chlorides including stannic chloride pentahydrate (SnCl4·5H2O) antimony(III) chloride (SbCl3) and ammonium fluoride (NH4F) for Sn, Sb and F sources, respectively. It is found that polycrystalline phase SnO2 of as-synthesized particles can be acheived by one-step sonochemical process while their crystallinity could be enhanced by post-calcination process. It is also acknowledged that their crystallinity, particle size, optical absorption and electrical properties are highly influenced by the incorporation of both F and Sb doping species. The prepared conductive oxide nanoparticles was mixed with tetraethyl orthosilicate (TEOS) and (3-Glycidyloxypropyl)trimethoxysilane (GLYMO) used as starting material for silica film. Composite films composed of a continuous silica matrix homogenously dispersed with F/Sb-codoped SnO2 (FATO) nanoparticles were deposited by sol-gel spin-coating process. Their morphologies and optical properties were investigated using field emission scanning electron microscopy and UV-Vis-NIR spectroscopy. Surface morphology images of the composite films exhibit of good dispersion of the conductive nanoparticles in the SiO2 matrix. Transmittance spectra of all composite films gradually decrease at longer wavelength with increasing F and Sb doping concentration. The results suggest the feasibility of this composite film application as IR-shielding coating layer of solar cell device depending on optimal doping concentration of F and Sb.

Resume : We report on high efficiency germanium quantum dot photodetectors (Ge QD PDs) fabricated by co-sputtering Ge and SiO2 targets on n-Si substrates followed by an annealing step to generate larger size QDs with better crystallinity. Subsequently, an ITO layer was grown as the top electrode. Finally, photolithography was performed to define variable area devices obtained by etching away the ITO and Ge QD/SiO2 layers using HCl which led to suppressed dark current, attributed to reduced periphery leakage. The PDs exhibited strong spectral photoresponse extending into the near infrared, leading to responsivities up to 2 A/W and IQE up to 400% over the 400?1100 nm wavelength range at reverse bias of ?10 V. Noise analysis was carried out yielding SNR up to 105 and specific detectivity D* = 6*1012 cmHz1/2W-1. The characterization procedure above was repeated as a function of temperature, mounting the PD into a cryostat and lowering the temperature down to 100oK. Approximately one order of magnitude of dark current reduction per 50oK of decrease was observed whereas the photocurrent values remained roughly unchanged at ?10 V. This resulted in lower thermal noise and in turn higher SNR and D* values, without negatively impacting the responsivity. These results suggest Ge QDs in an oxide matrix as a promising alternative material for high-performance PDs working in the visible to near-infrared spectral range, with particular improvement when operated in the low temperature regime.

Resume : Surface Enhanced Raman Scattering (SERS) effect is an interesting tool for various molecules sensing with very high sensitivity and specificity. This effect is obtained when target molecules were adsorbed on metallic surface of metals such as Au, Ag or Cu. Thanks to its large internal area and its ability for size selective molecule filtering, silicon nanowires (SiNWs) are suitable as a SERS substrate for sensing application. In this work, we combined the hierarchical nanoarray effect of SiNWs and the metallic surface of silver nanoparticles (AgNPs) to realize a SERS substrate for the Rodhamine 6G (Rh6G) detection at low concentrations. The SiNWs were prepared by metal–assisted chemical etching of n-doped Si (100) wafer. A Doehlert matrix method was applied for the analysis based on multivariate method in order to optimize the SERS response. Raman spectrum of R6G shows the appearance of some vibrational modes. Through NemrodW, the effect of silver nitrate concentration, AgNPs time deposition and time immersion in Rh6G solution on the response SERS were studied as well as the interaction between them. Also, the area characterized by a maximal SERS response was extracted. The most of influential factor is the immersion time of the SiNWs in the Rhodamine 6G solution. A limit of detection about 10-11 M was obtained for R6G molecules.

Resume : In this work we communicate the research towards the synthesis of laser-active nanocomposites representing a two-photon photostructurable laser-active polymeric platform for the fabrication of 3D optical elements. We focus on the material development using different synthesis techniques, providing detailed optical characterization and demonstrating sample structures. Various 3D-structurable photoluminescent formulations based on a perfluorpolyether urethane dimethacrylate matrix that is used as a photosensitive and non-quenching host medium are considered in this work. The optically-active characteristics were achieved using two distinct approaches: by directly dissolving salts, containing rare earth metal ions, or homogeneously embedding laser-active nanoparticles. For the latter, laser-active nanoparticles are synthesized either using a novel pulsed laser ablation technique enabling precursor-, contamination- and stabilizer-free fluorescent particulates, or by thermally-assisted nanocrystal synthesis. Micro-optical components were fabricated by two-photon lithography using these photoluminescent polymers. Material characterization, including measurements of emission/absorption spectra, optical losses, radiative lifetime and gain gives deep insights into its physical properties. We reveal that these materials have a high potential in integrated, disposable and recyclable laser-active optical components even on flexible substrates.

Resume : Non-volatile Resistive Random Access Memories are the potential candidates for the future memory devices due to their favorable scalability, simple capacitor like metal/insulator/metal (MIM) structure, low power consumption, simple fabrication steps, ultrafast switching speed and compatibility with current CMOS technology. Metal oxide layers showing resistive switching features, have significant potential to become fundamental building blocks of next-generation 3-D Resistive Random Access Memory (ReRAM) devices. Resistive switching (RS) is a phenomena in which the electrical resistance of a dielectric/insulating layer sandwiched between two metal electrodes is reversibly switched by externally applied electric field. The RS process in oxide based ReRAM devices is generally attributed to the formation and rupture of oxygen vacancies conducting filament, however the mechanism behind the RS phenomena in metal oxides still needs a great deal of discussion. Herein, we report the resistive switching characteristic of hydrothermally synthesized uniform size, single domain cobalt ferrite (CFO) nanoparticles using an FTO/CFO/Al sandwich structure. Close-packed thin layer of CFO nanoparticles was deposited on a fluorine-doped tin oxide (FTO) glass substrate by spray-coating method. The top aluminum (Al) contacts were deposited by e-beam evaporator using a shadow mask. Current-voltage measurements were performed to investigate RS properties of the fabricated FTO/CFO/Al structure. The I-V characteristics of the device were recorded at room temperature using a Keithley 2400 source meter with LabVIEW software, by applying the voltages in a cyclic manner, as follows: 0 V ? 4 V ? 0 V ? -4 V ? 0 V. Initially the device was in High Resistance State (HRS) and was switched into the Low Resistance State (LRS) by applying the positive bias voltage on the top Al electrode. Under the positive voltage sweep, when the current flows from top Al electrode to bottom FTO electrode, suddenly at a certain voltage the device was switched to LRS (ON state) from HRS (OFF state). Under the application of negative voltage the resistance was switched back to the HRS. It is to highlight that the RS behavior of FTO/CFO/Al device is obtained without any electroforming process, which is generally required in many RS devices. The reproducibility of the resistance states was confirmed by endurance test by switching the device between HRS and LRS for more than 100 cycles. The resistance ratio of HRS and LRS was observed to be always greater than 10^2 during this endurance test. The nonvolatile behavior of the RS device was examined by retention measurement, for time > 10^3 sec. The temperature dependent resistance studies of HRS presented a negative temperature dependence, which suggested the semiconducting nature of the device in HRS. However, the resistance of LRS showed an increase with increasing the temperature, which indicated the presence of a metal like state. Different transport mechanisms such as ohmic conduction, Poole Frenkel (P-F), space charge limited current (SCLC) and Schottky emission as well as the magnetic properties of the device have been investigated in different states (HRS and LRS), in order to understand the underlying conduction and resistive switching mechanism. In summary, this work demonstrates the fabrication of a non-volatile FTO/CFO/AL device exhibiting reversible, stable and electroforming free resistive switching features with a high resistance ratio (> 10^2) that persisted for a long time > 10^3 s.

Resume : Effects of plasmonic coupling between the metal nanoparticles and thin metal film separated by thin dielectric film-spacer have been studied by means of the light extinction in three-layer planar Au NPs monolayer / dielectric (shellac) film / Al film nanostructure. An influence of coupling on the spectral characteristics of SPR extinction peak in Au NPs has been analyzed at spacer thickness varied in the range of 3 – 200 nm. The main observed features are strong red shift (160 nm), non-monotonical behavior of the magnitude and width of surface plasmon resonance (SPR) at the decrease of the spacer thickness. An appearance of the intensive quadrupolar SPR peak has been observed at spacer thickness smaller than about 30 nm that is caused by the hybridization of dipolar and quadrupolar SPR modes in Au NPs in the presence of Al film. The appreciable enhancement (in 5.6 times) of light extinction by Au NPs monolayer in presence of Al film has been observed. It has been revealed that a certain value of dielectric spacer thickness (70 nm) exists at which such enhancement is maximal.

Resume : An effective permittivity of polymer composites (CMs) with randomly distributed electroconductive nanoparticles was considered within the Maxwell Garnett (MG) model in the microwave range. The modeling of effective permittivity showed that the content and parameters of conductive filler particles affect the frequency dependence of dielectric permittivity of CMs. So, it was found that at equal parameters of inclusions in CMs such as aspect ratio, electrical conductivity and content (lower than percolation threshold) the using of 1D (cylindrical shape) nanoparticles as fillers leads to sufficiently higher values of real and imaginary parts of permittivity and shifts the maximum of dielectric loss into lower frequency range of electromagnetic radiation (EMR) compared with 2D (disk-like) filler nanoparticles. It also was shown that increase of electrical conductivity of filler particles causes the shift of dielectric loss peak into the higher frequency range, while the values of dielectric permittivity did not change. The combination of 1D and 2D conductive particles allows extend the frequency range of dielectric loss in CMs varying the aspect ratio and electrical conductivity of fillers. This opens new possibilities for engineering the desirable frequency characteristics of nanocomposites, which determine the EMR reflection, absorption and transmission spectra.

Resume : Germanium (Ge) nanoparticles (NPs) have received much attention in the last years. On the one hand, the investigations of such systems are motivated by their unique size-dependent optical properties [1-2]. On the other hand, Ge NPs are non-toxic and bio-degradable that is an important task for their biological applications. In this work, we demonstrate that colloidal solutions of Ge NPs with controllable size can be easily obtained by femtosecond laser ablation of a Ge wafer in water and acetone. Transmission electron microscopy (TEM) measurements revealed crystalline structure of produced NPs with average size of 5-20 nm that is below Bohr exciton radius in Ge. It was also found that increasing in the pulse energy of ablation process leads to the decrease in average size of produced NPs. In addition, their optical properties were studied by absorption and Raman spectroscopies. A blueshift of absorption spectra as well as redshift of Raman scattering spectra of GE NPs were found indicating a change of their size. These results point out a perspective of Ge NPs for application in bionanomedicine. [1] S. Saeed, C. de Weerd, P. Stallinga et al. Light: Science and Applications 4(2) e251-6 (2015) [2] S. Vadavalli, S. Valligatla et al. Frontiers in Physics 2(57) 1-9 (2014)

Resume : Boron-doped silicon rich silicon oxide (SRSO) films are fabricated by radio frequency (RF) co-sputtering or PECVD followed by post-annealing treatment. It is found that the interface defects between the silicon nanocrystals (Si-NCs) and silicon dioxide matrix would change with the dopant increase which results in the variety of photoluminescene (PL). With the B-doped concentration increased, the intensity of PL from the Si-NCs is decreased and even quenched, while interface defects acting as luminescent centers dominate the PL. The interface defects including the weak oxygen bond (WOB), neutral oxygen vacancy (NOV) and Eδ’ centers are attributed to the origins of the luminescence. It is found that the ratio among these interface defects depends on the doping concentrations of B atoms. Hence, we can harvest color-tunable PL through the variety of interface defects controlled by the B doping.