Organized nanostructures and nano-objects: fabrication, characterization and applications

Resume : Monolayer doping (MLD) and monolayer contact doping (MLCD) offers a substantial advancement toward the controlled, ex-situ doping of nanowires using molecular monolayers as dopant source with uniform, self-limiting characteristics that is applied to the nanostructures post-synthesis and decoupled from the synthesis step. Accordingly, monolayer doping methods draw significant attention in recent years as evident by the vibrant activity in the field. The ability to form well controlled doping profiles at the nanoscale is especially appealing in the context of photovoltaic and photocatalysis. Developing a process which allows the formation of well-controlled, heterogeneous, and registered doping profiles in nanostructures without the application of high resolution lithographic methods pose a significant challenge to-date. This is because the combined requirements of symmetry breaking, control of chemical composition and registry at the nanoscale pose a significant challenge. In my talk I will present recent results obtained by a new monolayer doping methods developed in our group.

Resume : Nowadays with the modern developments in the semiconductor device technologies, conventional doping process has shown its limits such as high costs of equipments and their maintenance, crystal damage and necessity of multiple processing steps to achieve conformality. The last two drawbacks manifested especially in applications requiring 3D nanostructured Si surfaces. In 2008 a low cost technique for nanoscale controlled doping of semiconductors was reported [Ho et al., Nat. Nanomat. 7, (2008) 62]. It consists in the monolayer formation during the immersion of the sample in a chemical bath containing dopant precursors molecules and successive thermal treatment to diffuse the dopant. In order to understand the contribution of the surface doped layer on the electrical properties a new method, the chemical four point probe (C-4PP), has been developed. It consists in the repeated removal of thin layers of surface doped Si by using wet etches and successive 4PP measurements. Here we present a study of the oxide cap-layer effects on the migration of the carbon atoms constituting the precursor molecules. Two phenomena have been considered: the evaporation and the chemical bonding with the Si substrate. The measurements have been performed by X-ray spectroscopy analysis and C-4PP.

Resume : Deterministic doping of nanostructures is a key challenge for the fabrication of future advanced nanoelectronic devices. Unfortunately, a clear understanding of nanoscale doping is not available yet, as the physical mechanisms involved in this process are significantly different from those of bulk materials, due to additional constrains related to the presence of the interfaces and of the surrounding oxide matrix. In this regard, Si NCs embedded in a SiO2 matrix represent a paradigmatic system for the physical understanding of dopant incorporation in Si-based nanostructures. In this work the thermodynamic stability of P dopant impurities in Si nanocrystals at thermodynamic equilibrium is investigated. To achieve this goal samples with controlled diffusion sources that are spatially separated from the nanocrystals were fabricated and a controlled amount of dopant atoms from the dopant source was delivered to the nanocrystals by diffusing the dopants trough the SiO2 matrix. A simple model based on diffusion Fick’s law in one dimension was used to determine the energy barriers (1 eV) for P trapping/de-trapping at the SiO2/Si NCs interface, obtaining a complete picture of the system at equilibrium. The trapping efficiency was investigated as a function of the nanocrystal size.

Resume : The capability to control dopant incorporation within semiconductor materials with atomic accuracy represents a major challenge toward further scaling of electronic devices. A promising strategy is the monolayer doping (MLD), which consists in the creation of a well-ordered monolayer of dopant-containing molecules bonded to the surface of the substrate. In this work, we extended this approach by studying phosphorous (P) monolayer doping formation on SiO2 substrates through the “grafting to” of dopant-containing end-functional polymers. As the “grafting to” is a self limiting reaction, it is straightforward to produce a grafted layer featuring homogeneous thickness on a large area. In addition, the limiting thickness and the grafting density and consequently the phosphorous surface density, are controlled by the molar mass of the employed end-functional polymer. In more detail, two series of polystyrene and polymethylmethacrylate phosphate-terminated were prepared with molar masses ranging from 1500 to 20000 g/mol and narrow polydispersity indexes. These polymers were grafted to an activated silica surface by thermal annealing in a Rapid Thermal Processing (RTP) apparatus at 250°C for time periods ranging from few seconds to several minutes. Subsequent removal of the organic layer by oxygen plasma and capping with SiO2 leads to the formation of a P δ-layer embedded in a SiO2 matrix and spatially separated from the Si substrate. The amount of phosphorous bounded to the surface was determined by means of Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). By varying the molecular weight of the dopant-terminated polymer the control the final density of the dopant atoms was demonstrated.

Resume : The controlled formation and breaking of chemical bonds between organic molecules and single atoms attracts recently growing attention inspired by the interest in the fundamental knowledge of elementary processes occurring between the molecules and atoms. In particular, the controlled and reversible bonding between single molecules and atoms could be advantageous in construction of prototypical molecular switches, rotors and electronic circuits. In many applications the retention of originally designed electronic properties of polyaromatic platforms is crucial. It is expected that the problem of strong coupling of the electronic structure of the molecule with the metallic substrate could be resolved by application of passivated surfaces [1-3]. Among them, the hydrogenated semiconductors attract considerable interest due to possibility to create atomically precise artificial wiring comprised of surface dangling bonds [4-5]. Here we will characterize behavior of 3-input trinaphthylene and tris(biphenylene) molecules on the hydrogenated Ge(001):H substrate with the application of low temperature scanning tunneling microscopy/spectroscopy (STM/STS) supported by the advanced theoretical modeling. We will show that the molecules initially undergo a Diels-Alder [4+2] cycloaddition to paired surface dangling bonds [6]. It will be shown that with the application of the STM tip these chemical bonds could be reversibly formed and broken. Moreover, for the first time we will discuss the fabrication of a molecular rotor with a dangling bond bearing that could be operated by vibronic excitations with tunneling electrons. Further, it will be shown that by tuning the structure of the molecules the Diels-Alder attachment geometry could be controlled with high selectivity. Finally we will introduce prospects for utilization of the control over connecting individual molecules with surface single atoms. [1] Szymon Godlewski, Marek Kolmer, Hiroyo Kawai, Rafal Zuzak, Bartosz Such, Mark Saeys, Paula de Mendoza, Antonio M. Echavarren, Christian Joachim, Marek Szymonski, ACS Nano 7 (2013) 10105–10111 [2] Amandine Bellec, Francisco Ample, Damien Riedel, Gerald Dujardin, Christian Joachim, Nano Lett. 9 (2009) 144–147. [3] Szymon Godlewski, Marek Kolmer, Mads Engelund, Hiroyo Kawai, Rafal Zuzak, Aran Garcia-Lekue, Mark Saeys, Antonio M. Echavarren, Christian Joachim, Daniel Sanchez-Portal and Marek Szymonski, Phys. Chem. Chem. Phys. 18 (2016) 3854 [4] Marek Kolmer, Szymon Godlewski, Hiroyo Kawai, Bartosz Such, Franciszek Krok, Mark Saeys, Christian Joachim, Marek Szymonski, Phys. Rev. B 86, 125307 (2012) [5] Marek Kolmer, Rafal Zuzak, Ghassen Dridi, Szymon Godlewski, Christian Joachim and Marek Szymonski, Nanoscale 7 (2015) 12325 [6] Szymon Godlewski, Hiroyo Kawai, Mads Engelund, Marek Kolmer, Rafal Zuzak, Aran Garcia-Lekue, Gerard Novell-Leruth, Antonio M. Echavarren, Daniel Sanchez-Portal, Christian Joachim, Mark Saeys, Phys. Chem. Chem. Phys. 2016, DOI: 10.1039/C6CP02346K This research was supported by the National Science Centre, Poland (contract no. UMO-2014/15/D/ST3/02975) and the 7th Framework Programme of the European Union Collaborative Project PAMS (contract no.610446).

Resume : Gallium and indium oxide nanomaterials have been fabricated via carbothermal reduction using a chemical vapor deposition (CVD) method and employing gallium and indium oxide nanopowder mixed with graphite as source material. The growth has been carried out under flow of argon or argon mixed with oxygen. The resulting materials have been structurally and optically characterised using X-ray diffraction, scanning and transmission electron microscopy and related techniques, as well as photoluminescence and Raman spectroscopy, confirming their crystalline nature. To study the gas sensing properties, the nanowires were removed from the substrates applying sonication, followed by the deposition on suspended micro-hot-plates with pre-patterned electrodes and individual nanomaterials were contacted by combined Focused Electron- and Focused Ion-Beam assisted deposition techniques, as well as evaporated contacts defined by Electron Beam Lithography. The fabricated devices have been successfully tested towards several gases relevant in air quality control, such as NO2 and CO, at different concentrations and temperatures in a self-made test chamber.

Resume : Colloidal chemistry allows synthesizing monodisperse particles with diameters of only a few nanometers. Such structures possess a tiny electrical capacity. In transport measurements this results in the phenomenon of Coulomb blockade. Characteristic current oscillations have been observed in devices comprising individual nanoparticles (e.g. Andres et al., Science 272 (1996) 1323; Klein et al., Appl. Phys. Lett. 68 (1996) 2574). In my talk, I will demonstrate that by means of a gate voltage current modulations can be observed also in extended, monolayered films - realizing transistor function. The nanocrystal assembly by the Langmuir-Blodgett method yields super-crystalline, monolayered films over vast areas. A dielectric oxide layer protects the metal nanocrystal field-effect transistors from oxidation and leads to stable function for months. Comprehensive electrical measurements allow determining the reigning charge transport mechanisms. Such devices could be a new approach for low-cost electronic applications based on a new principle. References: * Yuxue Cai, Jan Michels, Julien Bachmann, Christian Klinke: Metal nanoparticle field-effect transistor, J. Appl. Phys. 114 (2013) 034311. * Hauke Lehmann, Svenja Willing, Sandra Möller, Mirjam Volkmann, Christian Klinke: Coulomb blockade based field-effect transistors exploiting stripe-shaped channel geometries of self-assembled metal nanoparticles, Nanoscale (2016) under review.

Resume : Poly(3,4-ethylenedioxythiophene) (PEDOT) is certainly the most known and most used conductive polymer since it is commercially available and shows great potential for organic electronic, photovoltaic and thermoelectric applications. Studies dedicated to PEDOT films have led to high conductivity enhancements. [1] However, an exhaustive understanding of the mechanisms governing such enhancement is still lacking, hindered by the semi-crystalline nature of the material itself. We report the development of highly conductive PEDOT films by controlling the crystallization of the PEDOT chains and by a subsequent dopant engineering approach using iron (III) trifluoromethanesulfonate as oxidant, N-methyl pyrrolidone as polymerization rate controller and sulfuric acid as dopant.[2] XRD, HRTEM, Synchrotron GIWAXS analyses and conductivity measurements down to 3 K allowed us to unravel the organization, doping and transport mechanism of these highly conductive PEDOT materials. N-methyl pyrrolidone promotes bigger crystallites and structure enhancement during polymerization while sulfuric acid treatment allows the replacement of triflate anions by hydrogenosulfate and increases the charge carrier concentration. We finally propose a charge transport model that fully corroborates our experimental observations. These polymers exhibit conductivities up to 5400 S cm-1 and transmittance at 550 nm between 80 and 96 % and thus show great promise for the replacement of ITO as transparent electrodes. [1] N. Massonnet, A. Carella et al, Chem. Sci. 2015, 6, 412–417 [2] M. N. Gueye, A. Carella et al, Chem. Mater., 2016 In press

Resume : In the last decade huge efforts have being put to use nanowires as building-blocks in functional electronic devices, and ease their integration to lower cost and power consumption. Their high surface-to-volume ratio, as well as well controlled physical and chemical properties are the key features towards toxic gases detection and environmental monitoring. In this work we present a novel gas sensor based on Ge nanowires. By means of a modified CVD method, its localized growth has been carried out on top of micro-membranes equipped with a buried heater, which requires a low power supply. In this way the deposition is focused right onto the sensing area, and with a negligible power budget of just few milliwatts, instead of tens –hundreds watts required by a conventional growth. We demonstrate that germanium nanowires react to the presence of both reducing and oxidizing gases acting as a chemi-resistor, similarly to metal oxide materials. Their surface is covered by a Ge oxide, whose thickness is maintained stable by working in a low temperature range. Ge NWs show a moderate response against the presence of NO2 and CO in a range of several ppm, diluted in synthetic air. Response has been observed even at room temperature, although a better yield is achieved working around 100ºC. This integrated structure provides a functional sensor with an excellent power performance under operation, of few mW for both heating and measuring.

Resume : The recently developed flame transport synthesis (FTS) approach by the group of Prof. Adelung has demonstrated the rapid and mass-scale production of three dimensional (3D) microstructured zinc oxide (ZnO) in various shapes ranging nanoscale one dimensional (1D) structures to nano- and microscale tetrapods or centimeter scale long wires [1]. An overview about the FTS approach, dependence of different experimental parameters on the resultant nano- and microstructures from metal oxide semiconductors will be presented. Electronic devices based on tetrapods, nano- and microneedles and 3D porous networks, etc. have been successfully fabricated and characterized in detail. These nanostructures based devices have been utilized for various sensing purposes. The tetrapods network based nanosensing device has demonstrated interesting gas/UV sensing characteristics.[2] Due to hexagonal-wurtzite crystal structure with non-center of symmetry, 1D structures from ZnO are quite good for piezotronics applications however this field still lacks with several issues in terms of proper nanoscale integrations and responses. Here, a piezotronic device based FTS grown ultra-long ZnO nano- and microneedle was investigated in detail and same will be presented.[3] The FTS grown ZnO nano- and microstructures offer a possibility of their further functionalization by loading their surfaces with interesting nanostructures, e.g., gold nanoparticles or fullerenes, etc. This leads to development of hybrid 3D nanomaterials which might be interesting for many technological applications and some preliminary results from these hybrid 3D nanomaterials will be demonstrated. References: [1] Particle and Particle Systems Characterizations 30, 2013, 775-783. [2] ACS Applied Materials & Interfaces, 7, 2015, 14303–14316. [3] Physica Status Solidi A 2016, (DOI: 10.1002/pssa.201532924)

Resume : Graphene based materials, such as carbon nanotubes and graphene, attract enormous research attention for their outstanding material properties along with molecular scale dimension. Optimized utilization of the graphene based materials in various applications requires the subtle controllability of their structures and properties. In this presentation, our recent research works associated to nanoscale organization and chemical modification of graphene based nanostructures will be presented. Carbon nanotubes and graphene can be efficiently organized into various three-dimensional nanostructures via self-assembly principles. The resultant carbon nanostructures with extremely large surface and high electro-conductivity are potentially useful for catalysis, energy storage and so on. Aqueous dispersion of graphene oxide shows liquid crystalline phase, whose spontaneous molecular ordering is useful for display or fiber spinning. In addition, the substitutional doping of graphitic carbon with B- or N- was achieved via pre- or post-synthetic treatment. The resultant chemically modified graphene based nanostructures with tunable workfunction and remarkably enhanced surface activity could be employed for organic solar cells, nanocomposites and dopant specific unzipping process for improved functionalities and device performances.

Resume : Metal oxide nanosheets are the oxide equivalents of graphene. They have thicknesses of 0.5 to few nm and lateral sizes up to tens of micrometers. Nanosheets are prepared by chemical exfoliation of layered metal oxides, and they can be assembled into densely packed 2D monolayer films using a Langmuir-Blodgett approach on any type of substrate, even curved or 3D patterned substrates. Since nanosheets are 2D single crystals with only one type of surface termination, they are versatile seed layers for oriented and epitaxial growth of subsequent functional metal oxide thin films. In this contribution the preparation and use of nanosheet films as seed layers for the formation of preferentially oriented nanoelectronic oxide films by pulsed laser deposition is discussed. Oriented perovskite-type SrRuO3, (La,Sr)MnO3, Pb(Zr,Ti)O3 and BiFeO3 films have been grown on Ca2Nb3O10 and Ti0.87O2 nanosheets. Depending on the nature of the seed layer, either [001] or [110] oriented films with properties depending on the orientation are formed. Moreover, the lateral sizes of the nanosheets are shown to offer an independent handle to modulate the properties of these films. Micropatterns of different nanosheets by photolithography and lift-off are demonstrated, illustrating the possibility to control the orientation of functional films even on micrometer-scale. The transfer of these films to temperature-sensitive substrates such as plastics is also discussed.

Resume : Hydrogen evolution technology is considered as a key element for the sustainable economic growth and generation of clean future energy [1]. Mostly platinum is applied in electro-catalytic systems for hydrogen evolution reaction (HER), and the development of new cost effective and durable materials which possess high catalytic activity for HER is necessary. The metallic Mo or its alloys can be used as active electrodes for hydrogen evolution [2]. Electrodeposits of metallic Mo can be obtained from non-aqueous and molten salt electrolytes [3]. Unfortunately, the pure Mo deposits cannot be obtained from aqueous molybdate solutions, but Mo easily codeposits with iron group metals (Ni, Co, Fe) [4]. It is known that such alloys demonstrate good electro-catalytic properties towards the hydrogen evolution reaction in both acidic [5] and alkaline solutions [6]. In this study Ni-Mo, Co-Mo, Fe-Mo rich in Mo alloys were electrodeposited onto copper substrates under galvanostatic mode from ammonia-acetate electrolyte. The highest amount of Mo (~ 52 at.%) was achieved at 30 mA/cm². At higher current density the content of Mo in the alloys decreases. The prepared coatings have an uniform thickness (10-30 µm), compact, dense and consisted of fine-grained crystallites. Electro-catalytic activity towards cathodic hydrogen evolution in 30 % NaOH solution in the temperature range of 25-65 °C on the electrodeposited Co-Mo, Fe-Mo and Ni-Mo alloy coatings by means of voltammetry. It was found that the exchange current densities for hydrogen evolution reaction increases with the temperature increase. The Co-Mo and Fe-Mo alloy coatings demonstrated the highest catalytic effect for hydrogen evolution reaction at 65 °C. It was determined that the exchange current density of hydrogen evolution onto Co-Mo and Fe-Mo deposits is ~ 0.45 A/cm², and it is considerably higher than that for Ni-Mo alloy coatings in the whole range of the temperatures. Acknowledgment. This study was founded from MSCA-ITN-2014-ETN No. 642642, and Research Council of Lithuania (MIP-031/2014). References [1] Züttel, A. Borgschulte, L. Schlapbach, Hydrogen as a future energy carrier. Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim, 2008. [2] N. Elezovic, B. N. Grgur, N. V. Krstajic, V. D. Jovic, J Serb Chem Soc 70 (6) (2005) 879-889. [3] H. Capel, P.H. Shipway, S.J. Harris, Wear 255 (2003) 917. [4] A. Brenner, Electrodeposition of Alloys, 2, Academic Press Inc., New York, 1963. [5] E. Navarro-Flores, Z. Chong, S. Omanovic, J Mol Catal A Chem 226 (2005) 179. [6] A. Subramania, A. R. Sathiya Priya, V. S. Muralidharan, Electrocatalytic cobalt-molybdenum alloy deposits. Int J Hydrogen Energy 32 (2007) 2843.

Resume : Semiconducting materials are a large family of chemical compounds presenting unique optical, electronic and mechanical characteristics and they have many promising applications in several different research fields. Moreover, when reducing the particles size to the nanoscale, their physical and chemical properties are enhanced which might lead to the development of smaller and more effective devices that could make a valuable contribution and revolutionize semiconductors industry. Different synthesis methods have been used to obtain semiconducting nanoparticles with certain geometrical attributes. In spite of the large number of possibilities, due to its high costs and complexity they are not most of the times applicable in industry. Therefore, there is an urgent need to develop simple and affordable methods to allow industrial scale fabrication of these nanomaterials. Regarding this, special attention has been placed on wet-chemistry methods, which have shown their great potential for the preparation of nanostructures with controlled shape and size. Wet chemistry synthesis based on long-chain amines are particularly interesting due to amines multiple role: as a solvent, surfactant and mild reducing agent. Their use in synthesis of 1D nanostructures has been previously described for several semiconducting compounds, while gallium/chalcogens structures have never been studied. In the presented work the synthesis of gallium sulphide and gallium selenide nanotubes in a mixture of hexadecylamine and dodecylamine is reported. It was found that the amines are homogenously intercalated within the nanotubes structure. Their optical properties make them promising for electro-optical applications.

Resume : Unlike graphene, development of 2D Si, often referred to as silicene, is overwhelmingly difficult due to the dominant sp3 hybridization in Si. Nevertheless, very much like graphene, 2D Si is expected to have exotic properties along with the advantage of being readily interfaced with the existing Si technology. In this work we demonstrate the development of quasi 2D sheets of crystalline Si by wet chemical exfoliation of layered silicide material (CaSi2). Samples have been formed as powder as well as colloidal dispersions in a variety of solvents. Development of nanocrystalline Si is evidenced from the distinct but broadened peaks of Si observed in x-ray diffraction (XRD) pattern. Flake like structures with lateral spread in the micrometer range and thickness of few nanometers are confirmed by electron and atomic-force microscopy. Electron diffraction studies also bear clear indication of nanostructuring along with crystalline features of Si. Colloidal suspension of the as-prepared quasi 2D flakes of Si exhibit bluish green luminescence under UV excitation that is detectable with the unaided eye. Spectroscopic signatures reveal that along with Si, oxide, hydride and hydroxide species are also present, which passivate the surface dangling bonds. However, the absorption and emission spectral characteristics of the sample are very different from bulk siloxene. The developed material serves as an excellent precursor for obtaining truly 2D silicene with tunable surface termination.

Resume : Quantum optics involves the coupling of quantum emitters to their electromagnetic environment. Because this coupling is related to the concentration of the optical field, it is typically constrained by the diffraction limit of light. One way to circumvent this is by moving to quantum plasmonics, which uses surface plasmon polaritons (SPPs) instead of photons. However, despite the advantages of this approach, quantum plasmonics has not yet been fully explored. It has been limited in large part by experimental difficulties in creating the necessary structures. We address this problem by combining state-of-the-art quantum emitters with plasmonic structures (waveguides and reflectors) that approach theoretical performance limits. We synthesize highly luminescent colloidal quantum dots (photoluminescence quantum yield >90%) and precisely place them on template-stripped silver surfaces. By proper design of such surfaces, high-quality plasmonic waveguides can be obtained. We demonstrate efficient coupling of the quantum-dot emission into guided plasmonic modes of such waveguides. In addition, by adding efficient reflectors, high-Q plasmonic resonators are created. More generally, the flexibility and fidelity of the resulting quantum-plasmonic systems indicates that they will allow a broad set of nanoscale quantum-optical measurements to be pursued.

Resume : Self-organized arrays of plasmonic nanostructures are confined on nanopatterned templates over large cm^2 areas. Highly ordered Au nanowire(NW) arrays are confined, by glancing angle deposition, on rippled glass templates prepared by direct Ion Beam Sputtering[1,2]. Steep faceted ripples with subwavelegth periodicity and length in the range of several microns drive the growth of tilted Au NWs endowed with dichroic optical response. For transversal light polarization Au NWs support a sharp Localized Plasmon resonance, easily tunable into the VIS spectrum by tailoring the NWs morphology, whereas the resonance is deeply shifted in the IR for longitudinal polarization. Furthermore, we investigate the feasibility of template assisted fabrication of Au NW dimers, in the form of tilted Au-silica-Au nanosandwiches. These kind of structures, also referred to as gap plasmonic nanostructures, have the potential to exhibit a high-Q magnetic-dipole plasmonic resonance, characterized by a strong near field confinement. Alternatively, two-dimensional arrays of plasmonic nanocrescents are confined on self-assembled monolayer of polymeric nanospheres [3], optimizing their efficiency as optical nanoantennas in SERS[4]. References [1]Giordano M.C. et al. "Template assisted growth of transparent plasmonic nanowire electrodes" submitted to Nanotechnology. [2]Belardini A. et al. Phys.Rev.Lett. 257401, 2011. [3]Robbiano V. et al. Adv.Opt.Mater.1,389, 2013. [4]Giordano M.C. et al. ACS Appl.Mater.Interf. 8,6629, 2016.

Resume : Abstract: Transparent conductive thin films are widely used in technologies such as solar cells, light-emitting diodes, and displays. The fabrication of these films is currently realized with thin films of transparent conductive oxides (TCOs), and in particular indium tin oxide (ITO). The as-made ITO transparent conductors suffer from limitations like costly fabrication process and brittleness. The use of solution-processable nanomaterials, and especially metallic nanowires, appears to be a promising alternative. Indeed it affords a large random two dimensional nanowire area, and low-cost deposition method with high performances [1]. Among metals, silver is the more mature process, copper has merely the same properties, with other advantages: price and abundance. Thanks to polyol (or hydrothermal for copper) process, metallic nanowires are synthesized in our laboratory. Silver nanowires have a mean length of 10 µm and a mean diameter of 60 nm whereas copper nanowires have a mean length of 54 µm and a mean diameter of 53 nm [2]. Their dimension confers them a high aspect ratio. Randomly dispersed on a substrate, at the percolation threshold, metallic nanowires lead to high performance, transparent and flexible electrodes. Many printing techniques are available to produce those electrodes in order to integrate them into devices such as thermal film heaters, thermochromic displays or touch sensors [3] [4]. Thanks to the use of spray coating, nanowire electrodes have excellent performance (i.e. R□<20Ω/□ at T>90%) [1]. Moreover stability of silver nanowire electrodes under ambient air is very promising since sheet resistance of electrodes is suitable with devices after four years of ageing. Stability of copper nanowire electrodes in air is shorter since sheet resistance is stable approximately for three months. The study will be focused on stability of electrodes under various stresses (electrical and environmental). More details will be given on stability of those electrodes in operating conditions and their reaction at different stresses. Part of the study will also deal with other nanomaterials synthesis, in particular core-shell nanowire synthesis. The purpose is to protect copper nanowires with a metallic shell to improve stability of the corresponding electrodes. Finally performance and stability under different environments of core-shell nanowire electrodes are studied and compared with copper and silver nanowire electrodes. Keywords: Organic, flexible and printed electronics / metallic nanowire/ transparent electrode References: [1] D. Langley, G.Giusti, C. Mayousse, C. Celle, D. Bellet, J.-P. Simonato, Nanotechnology, 24, 452001 (2013) [2] C. Mayousse, C. Celle, A. Carella , J.-P. Simonato, Nano Research, 7(3) : 315-324 (2014) [3] Celle, C., Mayousse, C., Moreau, E., Basti, H., Carella, A., & Simonato, J.-P. Nano Research, 5(6), 427–433. (2012) [4] Mayousse, C., Celle, C., Moreau, E., Mainguet, J.-F.

Resume : In this paper, we conduct a first trial study of size-dependent structural phase transition and morphological changes via thermal annealing of EDTA capped Zn0.45Cd0.55S nanoparticles (NPs) synthesized by chemical precipitation method with a crystallite size (DSch.) ≈ 2 nm. In addition, we focused on the interrelation between these changes and photoluminescence (PL) and optical absorption behavior of annealed and UV irradiated samples. The samples were characterized using XRF, XRD, FTIR, Raman, and UV-vis spectroscopy and HRTEM. It was found that increasing annealing temperature (Ta), results in structural phase transition from cubic to hexagonal structure at 400 oC due to size driven phase transition caused by sintering and grain growth accompanied by increase in the particle size and red shift of the optical band gap ("E" _"g" ^"opt" ). Normalized PL spectrum of Zn0.45Cd0.55S nanopowder at excitation wavelength 325 nm reveals new UV emission bands at 353 and 372 nm and blue emission bands at 406 and 468 nm. With increasing Ta up to 500ºC the PL intensity was quenched and red shifted. On the other hand, a colloidal solution of Zn0.45Cd0.55S NPs reveals emission bands at 388, 460, 504, 557 and 605 nm. To explain the mechanism of PL emission of the colloidal and powder Zn0.45Cd0.55S nanoparticles, trapping and recombination levels have been identified and the corresponding energy band diagrams were suggested. It was noticed that, UV irradiation of Zn0.45Cd0.55S colloidal solution leads to a decrease in the particle size and Urbach's tail state width accompanied by blue shift of Egopt, and enhancement in PL intensity. The overall enhancement in PL intensity was explained in terms of quantum size effect as a result of the reduction in the particle size by photocorrosion, surface modification by photopolymerization, formation of ZnSO4 and CdSO4 passivation layers and oxygen adsorption on Zn0.45Cd0.55S nanoparticles surface.

Resume : Although self assembly (SA) is a very common natural phenomenon that has been utilized in organic thin film synthesis, very few works have so far been done on SA of semiconductor nanostructures. Here we demonstrate formation of a thin film of luminescent nanocrystalline silicon by SA on air water interface. Silicon nanocrystals were prepared by a simple mechano-chemical technique and were subsequently functionalized by amphiphilic fatty acid. The film floating on air-water interface exhibit intense luminescence and can be viewed with the naked eye. Langmuir-Blodgett (LB) films of the functionalized silicon nanocrystals were formed on solid substrates by simple lift-off in an LB trough. Structural features were investigated using transmission electron microscopy (TEM) and electron diffraction which reveal nanocrystalline silicon with very small sizes in the range of 2-10 nm. Brewster angle microscopy (BAM) images provide strong evidence for formation of nearly monolayer of capped silicon nanocrystals film. We have observed the pressure versus area isotherms of the films in LB trough and tracked the hysteresis tendency. Spectroscopic investigation of functionalized silicon films reveal features that are very different from that of bulk silicon and clearly bears signature of nanostructures. These thin films hold immense potential for applications in opto-electronic devices.

Resume : Throughout the years, nanowires have become an essential material for optoelectronics. Free-standing semiconductor nanowires have recently attracted considerable attention due to their potential application in photovoltaic devices. The efficiencies of solar cells on nanowires have increased, reaching up to 13.8% for InP and 15.3% for GaAs materials. However, in order to further develop III-V nanowire solar cells, one still has to improve the quality of nanowires. Here in this work we have studied the influence of substrate preheating on growth of InP nanowires on (111)B substrates. The growth was carried out without using gold nanoparticles as a catalyst. All runs were carried out in an AIX 200 metalorganic vapour phase epitaxy (MOVPE) reactor. The source gases were TMIn and PH3. We achieved InP nanowires, the diameter of which varied. The quality of nanowires was inspected by means of XRD, XPS, SEM and Raman Spectroscopy.

Resume : The effectiveness of classical molecular dynamics (MD) simulations for the interpretation of x-ray absorption fine structure (XAFS) of thermally activated decomposition of diluted magnetic semiconductors (DMS), namely, (Ga,Mn)As after medium temperature post growth annealing was tested. To determine the local atomic structure around Mn atoms XAFS spectra at Mn K-edge were gathered at ~70 K at BL22 beamline, ALBA. The annealed samples show reorganization of the near edge electronic structure and dramatic decrease of FT(R) amplitude with annealing temperature increase. Such behavior is a likely indicator of redistribution/diffusion of Mn atoms in the host matrix (high disorder), allowing to propose the following working hypothesis: starting from the randomly distributed substitutional Mn (referred as monomers), and point defects like interstitial Mn and As/Ga vacancies, formation of non-regular distributed areas of ?N-mers? (dimer, trimer and so on combined through As) could occur, which eventually could lead to formation of Mn-rich (Ga,Mn)As clusters. Based on our hypothesis we constructed the model supercells which are expected to correspond to different stages of annealing process. Averaging set of instantaneous atomic configurations obtained from NVT classical MD simulations was used to construct modelled XAFS spectra. Analysis of modelled and experimental XAFS spectra showed that the signal is combination of signals coming from monomers, ?N-mers?, and vacancies.

Resume : Metallic Ni1?xVx alloys are known to exhibit a ferromagnetic to paramagnetic disordered quantum phase transition (QPT) at the critical concentration xc  0.114 in bulk. Such a QPT is accompanied by a quantum Griffiths phase (QGP), the physical observables in which follow nonuniversal power-law temperature dependences, in a finite temperature range on the paramagnetic side of the transition. In the present work, we explore the occurrence of QGP in nanoparticles of this alloy system. Nanoalloys with x in the neighbourhood of xc and mean diameter 18-33 nm were prepared by a chemical reflux method. Following a few microscopic and spectroscopic studies to determine the sizes, compositions and phases, dc magnetization measurements were also performed to seek out any signature of QGP in the nanoalloys. A paramagnetic-like increase of magnetization is observed to emerge below an x-dependent transition temperature TP(x ) within the blocked ferromagnetic state of the nanoparticles, and is corroborated by a peak at TP(x ) in the temperature dependence of resistivity. The magnetic susceptibility in this emergent phase follows a non-Curie power-law temperature dependence below 10 K for 0:09  < x <  0:14, indicating the presence of a QGP in the nanoparticles within these temperature and composition ranges.

Resume : III-nitride nanowires have large surface-to-volume ratio, nearly dislocation-free lattice, diminished strain, however their growth on inexpensive and strongly lattice-mismatched silicon substrates still needs further study. We report on the spatially-resolved photoluminescence (PL) study in self-organized GaN rods with InGaN/GaN core-shell multiple quantum well (MQW) structures. The samples with three QWs deposited on the GaN rod sidewall facets and emitting in the range from 450 to 530 nm were grown by metalorganic chemical vapor deposition (MOCVD) on Si(111) substrate. PL spectroscopy in confocal mode was exploited in a wide range of excitation intensities. Inhomogeneous MQW PL intensity distribution was observed on the sidewalls of the rods. The density of the bright spots, corresponding to large PL intensity, changes with the vertical position on the rod. The emission pattern is quantum-dot-like at the bottom and more uniform at the top of the rods. The PL band does not shift as the excitation intensity is increased, since there is no strain-induced electric field in the nonpolar crystallographic orientation of the MQWs. The PL from the MQW is polarized perpendicular to the c-axis, as it is expected for nonpolar InGaN structures. The emission polarization ratio has the highest value of 0.54 at the top of the rod but decreases down to 0.14 at the bottom. The results show that InGaN/GaN core-shell structures of good quality can be grown on low-cost silicon substrates.

Resume : PtCo alloys are well known with their high catalytic properties, good corrosion resistance and magnetic properties. The equiatomic Pt50Co50 phase with L10 crystal structure is the best candidate for magnetic storage applications with its high magneto crystalline anisotropy. Achieving such anisotropy lies on well controlled stoichiometry and the structure of the crystal. In order to understand and control its properties, PtCo samples must be prepared with well controlled manner. This study focused on the growt mechanism of PtCo and variation of Pt/Co ratio Two different type of substrate used in the study are Pt(111) single crystal and a SiOx (111) wafer. Pure Co and Pt50Co50 samples are prepared on these two different substrates by Magnetron Sputtering at various temperatures (RT, 300⁰C, 450⁰C, 500⁰C and 550⁰C). Elemental composition and stoichiometry of the samples are analyzed by XPS and AES. UPS is used to understand the electronic structure of surfaces and the electronic interaction of the Pt and Co under different preparation conditions.To investigate the epitaxial growth and determine the surface symmetry, low energy electron diffraction (LEED) has been used. Results of samples prepared on Pt(111) indicate for the Co diffusion through the platinum substrate by the increasing temperature. Furthermore, either the Co or PtCo films grown on P(111) above 450°C have the same stoichiometry, surface symmetry and similar electronic properties. Results of the samples prepared on SiOx indicate for a bonding formation between Pt and Si with the increasing temperature while there is a significant electronic structure change in Co.

Resume : In this report, described is a synthesis method for the preparation of GaN nanopowders from available GaE precursors (E = P, As, Sb) and discussed are competing reaction mechanisms operating during nitridation in the systems. High purity monocrystalline plates/chips of GaE (E = P, As, Sb) were either ground manually or using high energy ball milling. The resulting microcrystalline GaE powders were subjected to ammonolysis/nitridation under an ammonia flow at temperatures in the range 800-1100 C and for 6-150 h. Each of the precursors required specific conditions assuring complete nitridation. The substrates and the products were investigated by XRD supplemented with SEM/EDX, solid-state 71Ga MAS NMR, and Raman analysis. In all cases, the results confirmed the formation of pure nanocrystalline powders of GaN. Two GaN phases, i.e., hexagonal (h-GaN) and cubic (c-GaN), were often detected. For GaP, nitridation is thermodynamically controlled and yields pure h-GaN whereas for GaAs and GaSb some c-GaN is also formed supporting some contribution of topochemistry. In all precursor systems, the nitridation temperature and substrate particle size characteristics are key factors in controlling average crystallite size of GaN and the h-GaN/c-GaN ratio. Acknowledgement. The study was supported by the Polish National Science Center (NCN), Grant No. 2013/09/B/ST5/01223.

Resume : Development of advanced materials and structures for supercapacitor and battery is critical to achieve energy storage devices with high performance. Metal oxide/graphene hybrids can increase chemical and electrical coupling effects, and high surface area and electrical conductance of graphene are also attractive points as an advanced material for electrochemical devices. In this work, we present the selective growth of ZnO nanorod/reduced graphene oxide composites on graphene oxide film via IR laser-induced reaction. Optimized design of supercapacitor electrodes could be achieved by programming of laser scanning lines. The patterned complexes could be used as supercapacitor electrodes due to its pseudo capacitance (ZnO) and electric double layer capacitance (graphene).

Resume : The use of additional layers of alloying elements with a low surface energy such as Ag, Au, or Cu in films based on the Fe50Pt50 alloy can accelerate ordering processes in films by changing the stress state in FePt layer and leads to reduction of L10 phase formation temperature. Internal stresses in the film depend not only on the film thickness and the type of substrate, but on the heating and cooling rate during annealing as well. The purpose of this study was to investigate the effect of annealing in hydrogen and adding of the intermediate Au layer on hard magnetic L10 phase formation in the Fe50Pt50(15 nm)/Au(7,5; 30 nm)/Fe50Pt50(15 nm) films deposited onto SiO2(100 nm)/Si(001) substrates. Films were deposited by means of magnetron sputtering. Heat treatment of the samples was carried out in a hydrogen ambient with a pressure 100 kPa in the temperature range of 500ºС - 800ºС for 30 s. The crystal structures and phase composition of the as-deposited and annealed films were characterized by x-ray diffraction on Ultima IV Rigaku diffractometer. Electric resistance was measured by four-probe method. It was revealed, that disordered A1-FePt phase is formed in as-deposited films. Phase transition of A1-FePt L10-FePt starts after annealing in hydrogen at 500°C. The ordering degree of L10-FePt phase increases as the annealing temperature rised up to 800°C. Oriented grain growth of L10-FePt phase in the [001] direction does not occur due to the dissolution of hydrogen in the lattice of L10-FePt. This is evidenced by an increase in the lattice parameter of c and c/a ratio of L10 phase. It was also observed the formation of Au hydrides, which is accompanied by electric resistance growth. It is found that axial textures [111] Au and [111] FePt in films take place and are more evident in films with a thicker Au interlayer of 30 nm. The authors would like to thank Prof. Dr. M. Albrecht from Augsburg University (Germany) and workers for sample preparation, assistance in conduction of investigations and discussion of results. This work was supported by DAAD Leonard Euler Scholarship Program 2015 – 2016 (DAAD Grant № 57198300)

Resume : The use of FePt equiatomic composition films with ordered L10 phase as magnetic recording mediume can increase the density of the magnetic recording and storage information. This phase has a high magnetocrystalline anisotropy energy that prevents the superparamagnetic state transition with grain volume decrease. It is assumed that one of the ways to accelerate the process of ordering and decreasing the ordering temperature is to use the low surface energy of interfaces in the film composition and creation of stressed state by introducing an additional layer of the third element as Au, Ag or Cu. The aim of this work was to study the effect of Cu on magnetic hard L10-FePt phase formation in the layered [Fe50Pt50(15 нм)/Cu(7,5 нм)/ Fe50Pt50(15 нм)]n films, where n = 1, 2, at annealing in hydrogen. The films were deposited by magnetron sputtering on SiO2(100 nm)/Si(001) substrate kept at the ambient temperature. Annealing of samples in temperature range 5000С- 8000С for 30 s was carried out in a hydrogen atmosphere under pressure of 100 kPa. Phase composition and structure of the films was determined by X-ray phase analysis that was done on "Ultima IV Rigaku" diffractometer . It was established that the phase transition from the disordered A1 -FePt phase into the ordered L10-FePt phase begins after annealing at 500°C. In this case Cu is dissolved in the L10-FePt crystalline lattice that leads to reduction of c parameter. At increasing of annealing temperature an ordered ternary compound L10(FeCuPt) is formed and degree of ordering increases. The higher degree of ordering of L10(FeCuPt) phase is observes in multilayer [Fe50Pt50(15 nm)/Cu(7,5 nm)/Fe50Pt50(15 nm)]2 films. At the same time oriented grain growth of L10 (FeCuPt) phase in the direction of [001] is more evident in Fe50Pt50(15 nm)/Cu(7,5 nm)/Fe50Pt50(15 nm) films . The authors would like to thank Prof. Dr. M. Albrecht from Augsburg University (Germany) and workers for sample preparation, assistance in conduction of investigations and discussion of results. This work was supported by DAAD Leonard Euler Scholarship Program 2015 – 2016 (DAAD Grant № 57198300)

Resume : Magnetic quasi-0D well-defined nanoparticles are widely investigated in many research fields, and the most popular ones being medicine and environmental protection. The least toxic commonly studied compound is magnetite. The reason of popularity of magnetite in nano form is its low toxicity and good biodegradability. In general, nanoparticles exhibit superparamagnetic behavior, but their blocking temperature can differ not only due to size or composition, but also to synthesis procedure, and surface modification. In the presented paper, we have prepared hybrid ferrite nanoparticles doped with Ca2+, Co2+, Mn2+, or Ni2+ respectively. For functionalization of nanoparticles, succinic or phtalic anhydrides, and 3-phosphonopropionic or 16-hexadecanoic acids were used. In the next step, controlled tests of binding of such pollution elements as Pb, Cu, Cd were done. The most effective compounds are the best for purification of solutions including drinking water from selected elements (in this case, heavy metals). Characterization of studied nanoparticles was done by Transmission Electron Microscopy, X-ray diffraction, and Mössbauer spectroscopy. Composites before and after attachment of elements were analyzed by IR and Raman spectroscopy. Solutions containing selected tested elements were measured by AAS.

Resume : Diblock copolymers (DBCs) thin films have become the subject of an intense research activity because they self-assembly (SA) into periodic ordered nanostructures with different morphology. The DBCs containing polydimethylsiloxane (PDMS) have recently attracted a lot of attention because they form high-resolution nanostructures with dimensions below 10 nm, that can be exploited as nanolithographic masks perfectly suitable for microelectronic applications. The SA of the PDMS-containing DBCs can be achieved by means of different approaches but thermal annealing processes would be highly desirable. Interesting, the solvent employed to spin the DBC thin films plays an important role in the definition of the final morphology of the self-assembled nanostructures because the solvent could preferentially swell one of the blocks thus driving a specific morphology. In this work, we report a systematic study on the SA kinetic of cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) PS-b-P(DMS-r-VMS) thin film, with molar mass of 22 Kg/mol (d = 9 nm, Lo = 20 nm), by means of a Rapid Thermal Processing (RTP) machine on flat surfaces using solvents casting with fixed selectivity but different boiling points and densities. The SA kinetic was evaluated considering the evolution of the lateral order (ξ) as a function of the annealing time (t) that follow a power law dependence of ξ ~ t^Φ, where Φ provides information about the kinetic grain coarsening.

Resume : Electrical metal-semiconductor (Schottky) or semiconductor-semiconductor (p-n) junctions belong to basic elements of integrated circuits and various optical and-electronic devices. The key parameter of such elements is the presence of a potential barrier which determines its electrical behavior. The adjustment of the barrier’s electrical properties is thus very important. The general limitations of the primary methods (i.e. finding a metal/compound that produces the desired Schottky barrier height, or semiconductors doping) have been addressed in a number of studies and the respective solutions include insertions of organic molecular dipoles, insulating materials, and/or monolayer(s) of inorganic atoms, impurities, or defects at the interface. [1]. The use of self-assembled monolayers (SAMs) is a highly innovative approach to adjust surface properties of metals, metal oxides, and semiconductors. The Schottky barrier height depends on the work-function of the particular metal substrate surface. It was already shown that silver work-function can be finely tuned over a range of 1 eV by SAMs of oriented carborane dipoles (1,2-(HS)2-1,2-C2B10H10 and 9,12-(HS)2-1,2-C2B10H10) which are chemisorbed onto silver surfaces through their sulfhydryl (-SH) groups [2–4]. The placing of SAMs of oriented dipoles in a semiconductor-semiconductor interface has not been addressed despite its obvious importance and potential for the barrier adjustment. In this contribution, we present the first results of carborane dipoles adsorption on silicon (111) surfaces. PeakForce AFM and Kelvin Probe Force Microscopy have been used for the local mapping/distribution of the adsorbed molecules. [1] R.T. Tung, The physics and chemistry of the Schottky barrier height, Appl. Phys. Rev. 1 (2014) 11304. doi:10.1063/1.4858400. [2] J.F. Lübben, T. Baše, P. Rupper, T. Künniger, J. Macháček, S. Guimond, Tuning the surface potential of Ag surfaces by chemisorption of oppositely-oriented thiolated carborane dipoles, J. Colloid Interface Sci. 354 (2011) 168–174. doi:10.1016/j.jcis.2010.10.052. [3] J. Kim, Y.S. Rim, Y. Liu, A.C. Serino, J.C. Thomas, H. Chen, Y. Yang, P.S. Weiss, Interface Control in Organic Electronics Using Mixed Monolayers of Carboranethiol Isomers, Nano Lett. 14 (2014) 2946–2951. doi:10.1021/nl501081q. [4] A. Vetushka, L. Bernard, O. Guseva, Z. Bastl, J. Plocek, I. Tomandl, A. Fejfar, T. Baše, P. Schmutz, Adsorption of oriented carborane dipoles on a silver surface, Phys. Status Solidi B. 253 (2016) 591–600. doi:10.1002/pssb.201552446.

Resume : Asymmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) can form perpendicularly oriented nanodomains since the surface interactions are easily balanced by grafting the appropriate P(S-r-MMA) random copolymer (RCP) to the surface. The development of long-range lateral order is a key requirement for BCP integration in nanolithographic processes. The self-assembly of asymmetric PS-b-PMMA BCPs with molecular weight (Mn) ranging from 54 to 132 kg/mol over a 2 or 19 nm thick grafted layer was accomplished through a fine tuning of the annealing temperature (TANN) and time (tANN) in a rapid thermal processing (RTP) machine. The grafted RCP brush layer acts as a reservoir of solvent: the thicker the brush layer, the higher the amount of solvent available for the self-assembly of the BCPs. Scanning electron microscopy inspection of the samples at different stages of the grain coarsening process allows investigating the grain-growth as a function of the RCP brush layer thickness and determining the growth rates for each BCP as a function of Mn. For the 19 nm thick RCP brush layer, the collected data indicate that the cooperative effect of solvent and temperature is sufficient to sustain the grain coarsening process over the range of tANN we explored; for each specific Mn, the growth exponent is constant at all the explored tANN. However the growth rates change as a function of Mn ranging from 0.07 for Mn=132 kg/mol to 0.34 for Mn=54 kg/mol.

Resume : Germanium is having a renewed interest as a strategic material for applications in photovoltaics, mid infrared and gamma detectors and especially in nano-electronics as a possible high mobility channel material in nano-transistors. The doping of such material in a locally controlled and conformal way at nanoscale will be an enabling technology for the real application in nano-electronic devices. To this aim the molecular doping approach can be a very interesting option not yet investigated on germanium. In this paper we grip different phosphorous containing molecules to the Ge surface. We demonstrate that the chemical reaction is active on Ge surface as well on Si and SiO2. Quantification by means of XPS and nuclear reaction analysies shows that a layer containing 1.2 x 10^15 P atoms/cm2 forms at the germanium surface after a wet gripping procedure followed by the cleaning of the physically absorbed component by means of methanol. The P containing layer is separated by the bare Ge by a Ge oxide thin layer. For comparison the same procedure forms a layer with 7x10^14 P atoms/cm2 on both Si or SiO2 surfaces. The results concerning the dopant activation and diffusion after the evaporation of a SiO2 capping layer and thermal treatments will be presented.

Resume : Grafted multicomponent polymeric systems represent the starting point for the creation of scaled high-resolution polymer nanostructures including nanometer scale membranes, templates for fabrication of nanoobjects such as metal, ceramic nanodots and wires, and nanopattern masks for subsequent additive or subtractive processing of the underlying substrate. In addition, the exploitation of more sophisticated surface interactions, such as various directed self-assembly (DSA) approaches, can lead to structures featuring improved lateral ordering and reduced structural defects. From the analytical point of view, these systems can be conceived as ultrathin films (h < 10 nm) of polymer chains grafted to a solid substrate. Consequently, their evaluation represents a rather demanding analytical task due to the very small amount of material to be detected. Moreover, these materials should be analyzed still grafted to the substrate because their detachment from the surface implies major structural modifications. These two distinct requirements limit the number of analytical techniques suitable to obtain information about their structure and composition. The use of hyphenated thermal and mass spectrometric techniques is well established and widely applied to the investigation of the polymer structures under distinct thermal conditions. Recently in our laboratory a highly versatile TGA-GC-MS apparatus was developed1 and successfully applied2,3 to the analysis of a number of samples featuring substantial scale difference, i.e. bulk materials, thick films (few µm), thin (dozens of nm), and ultrathin films (few nm) without any sample pretreatments. In the present contribution, the TGA-GC-MS technique was addressed to the quantitative determination of the composition of ultrathin films obtained from the “grafting to” of functional PS-b-PMMA and P(S-r-MMA) copolymers. The calibration of the system was performed by model systems of functional P(S-r-MMA) with different composition. Once the system calibration was properly set up, the grafting process of binary mixtures of functional polymethylmethacrylate (PMMA) and polystyrene (PS) homopolymers to an activated and preferential silicon surface was elucidated. 1 Gianotti, V., Antonioli, D., Sparnacci, K., Laus, M., Giammaria, T. J., Ceresoli, M., Ferrarese Lupi, F., Seguini, G. & Perego M., J. of Chromatography A, 1368, 204-210 (2014). 2 Ceresoli,M., Palermo, M., Ferrarese Lupi, F., Seguini, G., Perego, M., Zuccheri, G., Phadatare, S.D., Antonioli, D., Gianotti, V., Sparnacci, K. & Laus, M., Nanotechnology, 26, 415603 (2015). 3 Antonioli, D., Sparnacci, K., Laus, M., Ferrarese Lupi, F., Giammaria, T. J., Seguini, G., Ceresoli, M., Perego, M. & Gianotti, V., Analytical and Bioanalytical Chemistry, doi: 10.1007/s00216-016-9380-8.

Resume : Tailoring surface energies is the key factor to control the orientation of nanoscopic structures in block copolymer (BCP) thin films. Perpendicular orientation of the BCP features can be achieved with non preferential interactions at both the bottom and top interfaces. A common approach to the formation of a neutral surface consists in using end-functional poly(A-r-B) random copolymers to induce the perpendicular orientation of polyA-b-polyB diblock copolymers. As the random copolymer chemical composition can be precisely controlled, a fine-tuning of the surface characteristics is possible. In this work, a series of hydroxyl terminated poly(styrene-r-methyl methacrylate) random copolymers was prepared, with equal composition but different molar masses, ranging from 1700 to 69000 g/mol. The Rapid Thermal Processing (RTP) technology was employed to perform flash grafting reactions of the random copolymers to the activated silicon wafer surface at different temperatures for time periods ranging from few seconds to several minutes. The characteristics of the grafted layer were delineated as a function of the molar mass of the random copolymers. The subsequent ordering propensity of a symmetric polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer was found to be dependent on both the grafting temperature and the molecular weight of the random copolymer employed. Efficient neutral wetting brush layers with thickness lower than 2 nm were obtained. These results shed new light on the nature of the surface neutralization and indicate that several concepts and preconceptions of the molecular design of the self assembling materials should be reconsidered.

Resume : Monodisperse colloidal spheres have emerged as the material of choice for a wide variety of applications that range from nanopattering to fabrication to photonic devices. These materials represent the simplest class of building blocks that can be readily assembled into two or three dimensionally ordered structures. A variety of colloids can be synthesized as truly monodispersed systems in which the size and shape of the particles and the net charges that are chemically fixed on their surfaces are all identical to within 1-2%. As the preparation of nanostructured materials involves essentially the use of monodispersed particles in the 10 nm to 1 micrometer size range, heterophase polymerizations are the techniques of election. They comprise a variety of different processes including suspension, dispersion, emulsion as well as nanoemulsion polymerizations. A related approach to prepare such nanosized particles relies on the seeded emulsion technique starting from seeds of a few nanometers. These can be prepared in situ by a self-seeding technique or can derive from a distinct preparation. In this presentation, we describe the preparation of PTFE/PMMA core-shell nanoparticles, featuring controlled size and narrow size distribution, through a seeded emulsion polymerization starting from a PTFE seed of 41 nanometers. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomer and the PTFE seed. The high degree of PTFE compartmentalization resulted in a very peculiar crystallization behavior of the resulting composite nanoparticulate systems[1]. Particles in the 100-350 nm range can be prepared with uniformity indexes suited to build 2D and 3D colloidal crystals. A linear correlation is observed between sphere diameter and stop band wavelength. As the diameter decreases, the stop band shifts to lower wavelengths. Angle-resolved transmittance measurements are performed with linearly polarized light with its electric field perpendicular (s-polarization) or parallel (p-polarization) to the incidence plane. With increasing angle of incidence, not only the position and intensity but also the shape of the transmittance peak modified, in a way strictly dependent from light polarization direction[2]. [1] M. Laus, K. Sparnacci, D. Antonioli, S. Deregibus, V. Kapeliouchko, G. Palamone, T. Poggio, G. Zuccheri, R. Passeri. On the multiple crystallization behavior of PTFE in PMMA/PTFE nanocomposites from core-shell nanoparticles. J. Polym. Sci. Part B-Polym. Phys. 2010 48 548-554. [2] E. Pavarini, L.C. Andreani, C. Soci, M. Galli, F. Marabelli, and D. Comoretto. Band structure and optical properties of opal photonic crystals. Phys. Rev. B72, 045102-1/045102-9 (2005).

Resume : In the content of this study, previously synthesized 3% by weight palladium incorporated MCM-41, MCM-48 and SBA-15 type catalysts were characterized by the XRD, BET, Chemisorption and SEM methods. All three catalysts had good crystalline patterns and high BET surface areas in the region of 600-900 m2/g. Highest BET surface area and pore volume was found for the 3%-Pd-MCM-48 catalyst due its three-dimensional pore structure while the 3%-Pd-SBA-15 catalyst had the largest active (metal) area. Incorporation of the palladium metal did not deteriorate the particle structure for the MCM-41 and SBA-15 type catalysts however it caused some agglomeration for MCM-48. Dispersion of the palladium metal was also highest for the SBA-15 type catalyst which suggests this catalyst probably will be the most active one in oxidation reactions.

Resume : Diblock copolymers (DBCs) are extensively investigated as key materials for lithografic applications. The integration of conventional top-down approaches with the bottom-up self-assembly allows DBC films to be employed as precisely registered organic templates. In order to satisfy the requirements of the industrial nanofabrication technology, lots of efforts are devoted to scale down the dimension of the DBC lattice parameters. However, DBC materials have a limitation of their self-assembly properties depending on the product between the Flory-Huggins parameter χ and molecular weight Ν. Conventional lithographic materials, like polystyrene-block-polymethylmethacrylate (PS-b-PMMA), show a low χ which limits their application at sub-10 nm scale, and therefore new high-χ materials have to be synthesized. In this work a series of PS-b-P(MMA-r-AF6) block copolymers (10 kg/mol) were prepared via ATRP with a gradient increment of 2-(perfluorohexyl)ethyl acrylate (AF6) units. The self-assembly events of these DBCs were studied by using a Rapid Thermal Processing (RTP) oven both on flat silicon surface and inside SiO2 periodical trenches. The fluorinated DBC thin films were characterized by contact angle, XPS and SEM analyses. A comparison between these high-χ materials and the conventional ones is useful to understand how tailoring the synthesis of fluorinated DBCs can help to overcome the imposed energetic limitation.

Resume : Achieving highly-doped shallow layers in germanium is a major challenge for advanced device development in many fields such as nano- and opto-electronics, photonics, sensors, etc. To this purpose pulsed laser melting, subsequent to ion implantation, is studied as being able to promote ultra-fast liquid phase epitaxial regrowth in a shallow layer. As a consequence, dopants are activated well above the equilibrium solid solubility while confining the diffusion within the molten layer. Latest results on electrical activation, diffusion, residual defects, contaminations, thermal stability will be presented for both p- and n-type doping of Ge in a wide range of experimental conditions.

Resume : Silicon- and Carbon- quantum dots (Si-QDs and C-QDs) have been recently proven to offer bright light emission with tunable color through the whole visible range [1-5]. Both materials are non-toxic and bio-degradable, can be (bio-) functionalized by virtually any organic molecule via strong covalent bond. Both can be prepared from resources that have virtually unlimited availability, such as sand, rice or bamboo for Si-QDs and various low cost organic materials for C-QDs. Si-QDs have also been shown in past to offer outstanding photo-chemical stability. This is in striking contrast to the currently employed nanostructures in optoelectronics or medical imaging, where health- or environment-risk materials (Cd, Pb, As, Zn, Se, …) or materials that are rare or expensive (In, Te, Rare Earths, Au, …) are in use. This situation occurs because Si-QDs have been known for inefficient and color-limited light emission [1] and C-QDs are still relatively new material with unresolved questions over origin of emission, stability and color-tunability [5]. In our work [1-4,6], we research optical properties of both Si-QDs and C-QDs, with goal to find the most efficient and broadly tunable light emitting system. As the size-dependent optical properties of semiconductor QDs make it difficult to uncover the origin of the underlying processes from ensemble spectroscopy only, we use combination of ensemble spectroscopy and single-QD-spectroscopy. This allows us to study properties of individual emitters that are otherwise obscured in ensemble measurements, like size-dependent emission spectra, blinking and size-dependent radiative rate. In particular, we focus on (i) possible enhancements of the radiative rate by ligand-induced modifications of the band-structure and (ii) spectral enhancements using induction of various color sites in both materials. [1] K. Dohnalova, K. Kusova, T. Gregorkiewicz, J. Phys.: Condens. Matter 26 (2014) 173201 [2] A.N. Poddubny, K. Dohnalova, Phys. Rev. B 90 (2014) 245439 [3] K. Dohnalova et al., Light: Science & Applications 2 (2013) e47 [4] K. Dohnalova et al., Small 8 (2012) 3185 [5] H. Nie et al., Chem. Mater. 26 (2014) 3104 [6] B. van Dam, H. Nie et al., “Multi-chromatic carbon dots”, in preparation (2016)

Resume : Three-dimensional nanoestructures combine properties of nanoscale materials with the advantages of being macro-sized pieces when the time comes to manipulate, measure their properties, or fabricate a device. However, the amount of compounds that have the ability to self-organize in ordered here-dimensional nanostructures is limited. Therefore, template-based fabrication strategies become the key approach towards three-dimensional nanostructures. Here we report the straightforward fabrication of a template based on anodic aluminum oxide, having a well-defined, ordered, tunable, homogeneous 3D nanotubular network in the sub 100 nm range [1]. The used fabrication approach includes a pulsed anodization process of aluminium, in which we anodize at constant voltage during Mild Anodization steps and at a defined current during the Hard Anodization pulses; followed by a chemical etching process, in which the aluminum oxide grown under HA regime is partially dissolved. The 3D-AAO thus formed possessed a hexagonal array of longitudinal nanopores (40 nm in diameter), perpendicularly interconnected through transversal nanochannels (20-35 nm in diameter). The number and the distance between the transversal nanopores can be simply adjusted selecting the amount and the length of the MA steps. The three-dimensional templates are then employed to achieve three-dimensional, ordered nanowire-networks in polymers. Lastly, we demonstrate the photonic crystal behavior of both the template and the polymer three-dimensional nanostructure. Our approach might stablish the foundations for future high-throughput, cheap, photonic materials and devices made of commodity plastics, for example. 1. Martín J, Martín-González M, Francisco Fernández J, Caballero-Calero O. Ordered three-dimensional interconnected nanoarchitectures in anodic porous alumina. Nature Communications. 2014;5.

Resume : Bottom-up processes like GLancing Angle Deposition (GLAD) of thin films and complex multilayers have attracted much attention in the recent years because of a large variety of technological applications in the field of photonic. The 3D nanostructures engineered exhibit optical, electrical and mechanical properties that differ from classical dense thin films. The GLAD process results, by a shadowing effect, to the conception of highly porous nanostructured materials. The morphology of theses 3D nanocolumns can be controlled by varying different deposition parameters like the substrate’s deposition angle, the deposition rate or the substrate temperature. A large panel of materials (oxides, semiconductors…) deposited by both sputtering and evaporation PVD in GLAD configuration, were studied for different depositions parameters. Our work is focused on the study of the relationship between the nanostructures (characterized by X-Ray Diffraction and SEM) and their optical properties through the modelling and the control of the refractive index gradient profile tuned by the porosity insertion. These optical properties were extracted from ellipsometric and spectrophotometric measurements made on a large spectral range going from the visible to the Midwavelength infrared. From this study we were able to obtain “new” optical properties leading to AR coatings with an ultra-high level of transmittance on a large wavelength range respectively in the visible and Midwavelength Infrared one.

Resume : Composites of self-organizing liquid crystal host phases and functionalized nanoparticles offer great opportunities both for basic science and new applications. In our present study we investigate the dielectric properties of nematic liquid crystal / gold nanoparticle composites and introduce new aspects to the fundamental understanding of interactions between nanoparticle dopants and liquid crystalline host phases: We report that functionalized nanoparticles contaminate the LC host phase with mobile ions and considerably increase its conductivity. Consequently, the electro-optic performance of such nanocomposites suffers from ion drift and interfacial polarization, phenomena which have been rarely associated with liquid crystal nanocomposites so far. We demonstrate that a simple space charge model provides a plausible explanation for the observed impact of nanoparticles on the electro-optic performance and is superior to alternative models reported in literature. Beyond probing the electro-optical performance, we use dielectric spectroscopy also to study dipolar relaxation modes of the host molecules in the presence of various dopants (nanospheres, nanorods). By analysing the impact of nanoparticles on the molecular relaxation times of the nematogenic molecules and the activation energy for molecular reorientation we find that the presence of nanoparticles, surprisingly, does not verifiably alter the uniaxial orientational ordering of the nematic host phase.

Resume : Silicon, an indirect bandgap semiconductor is one of the most important and intensively studied materials despite being an inefficient light emitter. Si with nano scale dimensions can be coaxed to emit visible light with relatively high efficiencies. Understanding the luminescence process in Si nanocrystals (NCs) has remained challenging. We have synthesised Si nano structures via an inexpensive technique of mechanical milling followed by deliberate oxidation-etching-oxidation. We subsequently successfully encapsulated these luminescent Si NCs inside a solid block of polystyrene. Structural and optical investigations reveal that polystyrene encapsulates and protects the Si NCs. Distinct peaks corresponding to Braggs reflection of (111), (220), and (440) of Si crystals are seen in the X-ray diffraction profile. Bright field Transmission Electron Microscopy (TEM) images showed some dark spots and fringes which are signatures of Si NCs. From the optical characteristics it is seen that the Uv-visible absorption commences from 410 nm with a peak at 290 nm. Photoluminescence spectra of the nanocomposite shows highest intensity of emission at ~ 420nm.Thin film of polystyrene encapsulated Si NCs was spin coated on a Transparent conducting oxide (TCO) sandwiched between a Electron Transport Layer (ETL) of Alq3 and Hole Transport Layer (HTL) of PEDOT.PSS. Ohmic contacts were established to form a device which emits room temperature electroluminescence detectable with unaided eye.

Resume : Plasmonic nanostructures enable the concentration of light to the deep subwavelength regime and, thus, are the topic of intense fundamental and application oriented research. Nanoparticles acting as optical antennas are well known for their nanoscale mode volumes, due to the excitation of localized plasmon modes. In this context electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) became a powerful technique as it enables to map the full modal spectrum of plasmon eigenmodes with unprecedented high spatial resolution [1]. In this work we present an EELS study of plasmon eigenmodes on single metallic nanoparticles prepared by means of electron beam lithography. First we identify two different types of plasmon modes on silver nanodisks, i. e. film and edge modes [2]. Second we show that coupling of edge plasmon modes within a single rectangular nanoparticle leads to mode splitting and the formation bonding and antibonding edge modes. These experimental observations together with a theoretical study in the form of boundary element method (BEM) simulations [3] lead us to universal scaling rules, connecting the nanodisk spectrum to the surface plasmons of extended films and edges. Furthermore the coupled edge mode model straightforwardly explains the mode energies in dependence of the nanoparticle geometry and is thus an effective tool for the understanding and tailoring of plasmonic mode spectra. [1] Nelayah et al., Nat. Phys. 3 (2007), 348−353. [2] F.P. Schmidt et al, Nat. Commun. 5 (2014), 3604. [3] U. Hohenester and A. Truegler, Comp. Phys. Commun. 183 (2012), 370. [4] This work was supported by the FWF SFB NextLite (F4905-N23 and F4906-N23), ESTEEM2 (FP7 project, no. 312483), NAWI Graz, and the Graz Centre for Electron Microscopy (ZFE).

Resume : This talk will present a self-aligned nanowire bonding process to form free-standing point-to-point electrical connections[1]. Wire diameters down to 200 nm and contact pads down to 1 µm will be shown. Moreover, the process is a parallel process to achieve a higher throughput when compared with any of the emerging serial-direct-write or established serial wire bonding methods. The presented process is based on a method that is best referred to as “gas phase electrodeposition”. The process has been described in parts before[2,3]. The relevant elements as it is known so far are briefly described to put the current research in context. First it is a localized material growth/deposition process which uses charged insulators to attract[4] or deflect[5] an incoming flux of charged material. Taking a closer look at the basic process, it becomes clear that gas phase electrodeposition shares some of the characteristics of electrodeposition in the liquid phase. However, it is a gas phase process with a much larger mean free path of the particles. The Debye length representing the screening length of Coulomb forces is also larger[6]. Despite this difference, it can grow nanostructures in selected domains in a programmable fashion by adjusting the dissipation current of the ionic species that arrive at the surface. For example, in the simplest case it was used to grow straight metallic nanowire arrays whose height and density were adjusted to vary across the substrate which in turn were used as contacts in photovoltaic devices[3]. Others have used this technique to fabricate metallic nanostructures for surface enhanced Raman spectroscopy (SERS)[7,8]. In any event, charged material continues to deposit into locations where charge dissipation can occur, leading to a growth of extended structures much like what is observed in the liquid phase based electrodeposition/plating. References [1] J. Fang, L. Schlag, S. C. Park, Th. Stauden, J. Pezoldt, P. Schaaf, H. O. Jacobs, Advanced Materials, 2016, 28 (9). [2] J. J. Cole, E. C. Lin, C. R. Barry, H. O. Jacobs, Small 2010, 6 (10). [3] E. C. Lin, J. J. Cole, H. O. Jacobs, Nano Letters 2010, 10 (11). [4] H. O. Jacobs, G. M. Whitesides, Science 2001, 291 (5509). [5] A. M. Welle, H. O. Jacobs, Applied Physics Letters 2005, 87 (26). [6] C. R. Barry, H. O. Jacobs, Nano Letters 2006, 6 (12). [7] E. C. Lin , J. Fang , S. C. Park , T. Stauden , J. Pezoldt, H. O. Jacobs, Advanced Materials 2013, 25 (26). [8] J. Fang, S. C. Park, L. Schlag, T. Stauden, J. Pezoldt, H. O. Jacobs, Advanced Functional Materials 2014, 24 (24).

Resume : Two (2D) and three (3D) ordered assemblies (supracrystals) have been prepared by dropwise deposition and immersing process respectively,(1) of a colloidal solution of Co nanoparticles, which size control have been obtained through a new chemical route, allowing TEM and Raman (low wavenumber) characterization. Chemical reduction of Co(AOT)2 precursors with NaBH4 and solvent selection (isooctane, hexane, cyclohexane, xylene, cumene, decane, octane) leds to uniform cobalt nanoparticles with tunable size ranging from 3.9 to 9.3 nm and their 2D and 3D ordering. TEM was performed using a JEOL JEM-1011 microscope operating at 100 kV, a JEOL 2010 microscope at 200 kV and a Nion Ultrastem 100 scanning transmission electron microscope operating at 100 kV. A HR800 LabRam setup from Horiba Scientific Jobin Yvon, working with 514.5-nm laser excitation and equipped with BragGrate notch filters were used. We report here the first observation of (polarized) low wavenumber Raman signature of ordered assemblies with particles ranging from ~4 to 9 nm in the 100-350K temperature range (2). The mode at the lowest wavenumber, pointed at 3 to 10 cm-1, is attributed to the quadrupolar (l= 2) mode while the second one, at 17 to 25 cm-1, is attributed to the breathing Lamb’s mode (l = 0). The wavenumber of these modes is reciprocal to the inverse particle diameter as was confirmed analyzing different particles with different size developed recently(3) . This observation shows that Plasmon-phonon coupling is not mandatory to observe Lamb’s metal particle modes if high sensitivity high resolution instruments are used. Furthermore, we point out the utility of Low Wavenumber Raman Spctroscopy to determine the average particles size. 1- I. Lisiecki, P.A. Albouy and M.P. Pileni Adv. Mat. 15 (2003) 712. 2- G. Simon, L. Meziane, A. Courty, I. Lisiecki, Ph. Colomban, J. Raman Spectrosc. 47 (2016) 248. 3- S. Costanzo, G.Simon, J. Richardi, Ph.Colomban end I.Lisiecki. Submitted to Chemistry of Materials.

Resume : J-aggregates still have attracted attention although their applications to photography have gone out of use. Because of their low dimensionality, macroscopic orientation enhances their properties in a direction, thereby being favorable in applications such as nonlinear optics and semiconducting devices. We report here the J-aggregates oriented on aligned polytetrafluoroethylene (PTFE) layers. They are partially formed in the films from 5 dyes deposited on the layers. Large dichroic ratios (D) due to high orientation are often shown: two dyes show D from 20 to 44 in polarized absorption spectra. The film of a bisazomethine of the two also has been successfully applied to ambipolar organic field effect transistors. We sometimes have the substrate effect where J-aggregates are not formed on glass, demonstrating the induction of J-aggregates by the layers. The origin of the effect will be discussed in terms of the driving force of the orientation. The effect suggests its advantage: the oriented aggregates could be obtained from various molecules. [1] T.Tanaka, et al., J.Phys.Chem.C,115,19598(2011); [2] T.Tanaka, et al., Chem.Lett.,40,1170(2011); [3] T.Tanaka, et al., Chem.Lett.,42,34(2013); [4] T.Tanaka, et al., Chem.Lett.,44,462(2015); [5] T.Tanaka, et al., Langmuir, 32,4710(2016); [6] J.C.Ribierre, et al., RSC Adv.,4,36737(2014).

Resume : Intracellular pH sensing is a key diagnostic tool for many biological mechanisms, such as ATP hydrolysis, cancer formation and brain or heart diseases. Photoluminescence (PL) microscopy with conventional pH sensors is limited by the need of radiometrically measuring their PL intensity in biological samples. This is boosting the interest for multifunctional probes with ratiometric response arising from the different pH sensitivity of co-existing emissive states. Current ratiometric probes are complex systems consisting of inorganic nanostructures coupled to organic dyes, which suffer the poor stability of organic systems and cross-readout issues due to their broad PL spectra. Here, we overcome all these limitations by demonstrating the first ratiometric single-particle pH probe based on fully inorganic nanocrystals (NCs) featuring high stability and narrow PL spectra. We use bio-compatiblized dual emitting core/shell CdSe/CdS NCs exhibiting core and shell PL with different pH sensitivity due to the different exposure of the respective excitons to the environment: the core PL is unaffected by the pH, while the shell PL undergoes drastic enhancement in the 3-11 pH range, resulting in a cross-readout-free ratiometric response of 600%. In vitro microscopy of HEK cells demonstrates that the ratiometric response in biologic media fully resembles far field pre-calibration PL experiments, which we further use for real-time monitoring an externally induced pH variation in living cells.

Resume : The direction and motion of cells have a key role in many physiological processes, such as tissue morphogenesis, or embryonic development. These interactions are regulated by the chemical surface properties of the biomaterial and its surface topography. Topographical modifications of surfaces (µm and nm) are known to induce changes in cell shape and adhesion, thereby affecting cell behavior. The control of the cell contact guidance is very promising. Ko and al. have shown that the junction angles, can modulate the motion speed of cells without altering their directionality. Generally speaking, in its environment, the cell is not confronted to structures having strict corners, but to curved structures. Anselme and al. have studied that the influence of curved structures on cell behavior and Laser Induced Periodic Surface Structures (LIPSS) in static mode separately. In this work, the structures which were both curved and multi-scale patterned were designed and their influence on cell behavior was studied. TA6V is one of the most commonly used metallic alloys in biomedical applications. A femtosecond laser was used as a surface texturing technique in order to create multi-scale structures on the TA6V surface: material ablation (30µm) and generation of LIPPS (~600nm). The present work focused on stem and marcrophage cells motion (position, direction and speed) within multi-scaled structures to verify whether the LIPSS has a competitive or a complementary effect on cell movement.

Resume : The field of electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) has recently achieved successes linked with the development of aberration correctors, enabling atomically-resolved spectroscopy. Also, a new generation of monochromators is emerging, providing improvements in energy resolution and unprecedented access to low energy-loss ranges (optical and near IR spectral ranges). Similarly, recent progress in the collection of visible-range photons emitted by a sample has enabled novel cathodo-luminescence (CL) experiments in STEM. In addition, new ways of exploiting fast electron beams, including combining them with photon beams, have opened up the field of nano-optics, providing a high-spatial resolution alternative to conventional optical techniques. Examples will be given on the use of spatially-resolved core-level excitation signals for quantitative measurement of electron densities (charge accumulation) [1] or 2D electron gases at interfaces in oxide-based nanodevices. Developments in EELS and CL for reaching plasmon signatures down to the IR spectral range will be described, allowing the mapping of eigen modes in plasmonic nanostructures and a deep understanding of the physics of these excitation [2]. New possibilities for exploring the link between a crystal structure (h-BN), its defects and its emission properties as revealed by nano-CL [3] and original quantum nano-optics experiments will be discussed [4]. [1] M. Marinova et al, Nano Lett., 2015, 15 (4), 2533 [2] A. Losquin, et al, Nano Lett., 2015, 15 (2), 1229 [3] R. Bourrellier et al, ACS Photonics, 2014, 1 (9), 857 [4] R. Bourrelier et al, to appear in Nanoletters.

Resume : Strained core-shell heterostructure nanowires are predicted to possess significant strain-induced lateral piezoelectric fields, which can provide a mechanism for efficient charge carrier separation and collection in a photovoltaic device. In this work, we investigate the material quality and optical properties of vertical GaAs/InGaAs core-shell nanowire arrays grown on n-type Si(111) substrate by molecular beam epitaxy using two approaches, namely self-assembled growth of randomly-positioned nanowires, and selective-area growth of periodic nanowire arrays. The self-assembled growth is performed on Si substrate covered with a controlled chemical oxide layer, while the selective-area growth is enabled by a nano-patterned thermal silicon dioxide mask on Si. Ga catalytic droplets are deposited in situ to initiate the growth of GaAs core nanowires via the well-known vapour-liquid-solid mechanism. We demonstrate how to improve compositional homogeneity in the InGaAs shell and successful p-type doping of the InGaAs shell to create a radial p-n or p-i-n junction device structure.

Resume : Self-assembled hierarchical nanostructures comprising branched nanowires (NWs) are interesting for both fundamental research and potential applications. Even though the formation of branched NWs is quite easy to achieve, their controlled assembly is nontrivial and yet not well understood. Here we report on branched III-V semiconductor (GaAs) NWs grown by molecular beam epitaxy (MBE). The growth of NW branches can be achieved by a number of methods; we focus on two of them: (i) manipulation of the Au catalyst nano-droplet shape/position, (ii) deposition of secondary catalyst at the side-walls of primary NW trunk. In the first case we changed the composition and position of Au nandroplets by exposing already grown GaAs NWs first to As and then to In fluxes, at temperatures slightly lower than those applied to GaAs NWs growth; in the second approach the catalyst nandroplets/nanocrystals were formed at the sidewalls of primary GaAs NW trunks, and then generated the growth of NW branches. Two different types of secondary catalyst have been exploited (1) liquid phase Bi nano-droplets and (2) solid phase MnAs nanocrystals. The growth of branches proceeded then either in the vapor-liquid-solid (VLS), or vapor-solid-solid (VSS) NW growth mode; in the cases (1) and (2), respectively. We have observed significant differences in properties of branches generated on zinc-blende or wurtzite sections of primary GaAs NW trunks in both cases. The HRTEM, EDXS structural analysis is performed.

Resume : Semiconductor or metallic nanocrystals embedded in dielectric matrices have attracted great attention over the last decade for many electronic and optoelectronic applications. In particular, Ge nanocrystals are discussed as charge storage nodes for nanocrystal based nonvolatile memory devices [1]. However, synthesizing Ge nanocrystals in ZrO2 based high-k matrices a simultaneous crystallization of Ge and ZrO2 has been reported previously [2]. In case of nonvolatile memories amorphous dielectrics are rather desired than multi-crystalline ones since grain boundaries act as paths for leakage currents supporting the discharging of the nanocrystals across the blocking oxide. In the present work, phase separation, nucleation, and crystallization processes in tantalum-containing ZrO2 (TaZrOx) and Ge-TaZrOx were investigated. For this purpose, 500 nm thick TaZrOx and Ge-TaZrOx films with various Ge-concentrations were deposited by rf magnetron sputtering. Size, shape, and spatial distribution of the Ge nanocrystals were determined by transmission electron microscopy. Varying the annealing temperature the crystallization processes were studied by X-ray diffraction and Raman scattering. In comparison to ZrO2 as dielectric matrix a temperature window between 650°C and 750°C can be be used in order to synthesize Ge nanocrystals within an amorphous TaZrOx matrix. [1] D. Lehninger et al.: Appl. Phys. Lett. 106, 023116 (2015) [2] S. Haas et al.: J. Appl. Phys. 113, 044303 (2013)

Resume : The technique of nanosphere lithography uses hexagonally close packed mono- or double layers of spheres as masks for site-controlled manipulation of the substrate surface. This enables a cost-effective patterning of large surface areas. For many applications of such patterned surfaces a narrow size distribution of features, i.e. of mask openings is essential. Therefore, the present contribution reports on an automated SEM image analysis of sphere monolayers and their interstices, with focus on the correlations between the sphere diameter, sphere position and interstice size distributions. In order to detect and evaluate the individual sphere diameters and positions iterative cross-correlation, multiple-angle intensity profiling, sphere edge point detection and fitting algorithms are applied, enabling a sphere detection efficiency of at least 99%. Moreover, the size of the interstices between the sphere triples are quantified by intensity thresholding. In this presentation we analyze how the sphere size distributions as well as the sphere position variations contribute to the observed interstice size variations of polystyrene nanosphere monolayers for average sphere diameters in the range between 220 nm and 618 nm. The findings are corroborated by simple geometric models, which use the fitted sphere diameters and positions as input data.

Resume : The magneto-optical and vibration properties of nanostructures are determined by density functional theory, time-dependent density functional theory and many-body perturbation theory. The results demonstrate the predictive power of these theories by showing that the complex interplay of defects inside the nanoparticles, surface termination and the size of nanoparticles set the basic properties of semiconductor nanoparticles. These theories are applied to design nanoparticles for desired applications. Particularly, we will show examples on single photon emitters for quantum technologies, fluorescent nanoparticles for in vivo biomaging where the corresponding successful experiments were driven and understood by theory.

Resume : To control the exact position of semiconductor nanostructures, especially quantum dots (QDs), is important for incorporating these nanostructures into novel semiconductor devices. Although self-assembled growth can produce very high quality QDs either by strained layer or droplet epitaxy, the position of the dot formation is random. An approach to overcome this limitation is to use a combination of self-assembly and selective area epitaxy (SAE). SAE is a kind of template method, which allows for laterally patterned material deposition. By making the size of the area equal or smaller to the mean distance in self-assembled growth, it should be possible to position of a single nanostructure with high accuracy. In this contribution, we present a shadow mask approach for SAE in the InAs/GaAs-system. The mechanical mask is realized on a SiN-membrane base by employing nanofabrication technology allowing for hole diameters down to 100 nm. The membrane is fabricated from a Si-wafer covered with 100 nm Si3N4 by anisotropic chemical etching of Si(100) applying KOH. The membrane itself is patterned by electron beam lithography and reactive ion etching. The tests show that the mask is fully compatible with ultra-high-vacuum and can withstand temperatures up to 850°C, i. e., it is compatible with our molecular beam epitaxy process. GaAs layers, which are deposited on the top side of the mask, result in a reduction of the hole size in the membrane and they can be re-evaporated without damaging the mask. The first deposition tests through the mask show selected area deposition of Ga droplets, which can be converted to GaAs QDs.

Resume : Single-crystalline oxide thin films supported by metals are a well-accepted class of model system for studying fundamental aspects of oxide surface and thin oxide layer chemistry and physics [1]. In the present contribution, we report on our efforts to expand this model approach to electrochemical studies on well-ordered oxide surfaces. Single-crystalline FeO(111) and Fe3O4(111) films were grown under ultra-high vacuum (UHV) conditions on a Pt(111) substrate and subsequently transferred into air or brought into contact with various aqueous solutions [2]. We have tested the stability of the oxide layers in these environments and characterized their electrochemical properties by cyclic voltammetry. The surface morphology and potential-dependent surface structure changes were investigated in-situ by electrochemical scanning tunneling microscopy (EC-STM) and potential-controlled sum frequency generation spectroscopy (EC-SFG). The influences of ionic strength and pH value on the oxide-water interface were examined. Finally, two different organic compounds (Catechol and Aminophthalic acid) were deposited in UHV and from solution and were investigated by electrochemical and UHV methods. [1] W. Weiss, W. Ranke, Prog. Surf. Sci. 2002, 70, 1-151. [2] H.-F. Wang, H. Ariga, R. Dowler, M. Sterrer, H.-J. Freund, J. Catal. 2012, 286, 1-5.

Resume : Heteropolynuclear (HPN) organometallic compounds (OMC) are attracting great interest since long ago. In these products, several proximal metals with various oxidation numbers and spin states coexist in different crystalline environments. The mutual interaction between these ions may modify their stability or catalytic and biological activity, and opens a bunch of applications with potential impact in Materials Sciences (as precursors for new materials) and new technologies (as single molecular magnets). Due to the increasing interest of the incorporation of Fe(II) or (III) in polymetallic arrays and previous experience in Zn(II) polymers (E-MRS Fall 2015), the synthesis of new HPN derivatives with Zn and Fe(II) or (III) has become one promising challenge. Here we present the synthesis and characterization of a new decametallic (Fe6Zn4) OMC prepared at room temperature. Its crystalline structure confirmed the presence of molecules where a 4 Zn(II), sited on the vertex of a trigonal pyramid, form the internal core and the Fe(II) ions are peripherally distributed and connected to the Zn(II) through O-donor ligands. As a consequence of this arrangement of metal ions, the molecular shape resembles a sphere (ca. 16 Å diameter). This type of metal ions distribution in the molecule has no precedent. Since the decomposition products depend on the particular atmosphere, further studies concerning its thermal stability in N2 and air and its potential applications will be also presented.

Resume : Nanosphere lithography (NSL) attracted growing interest in nanotechnology for the realization of well-ordered and regular patterns at nanometric scale. NLS is indeed an inexpensive and versatile method that has found many practical applications such as the fabrication of nanowires, SERS substrates, charge trap flash memories, optical devices and LEDs surface texturing. However, one of the main factors limiting the use of NSL in large-scale lithography is the inhomogeneity of the self-assembled layer after spin coating process. A possible solution to this problem is the use of directed self-assembly of the nanospheres inside topographically defined patterns. In facts, this approach is able to combine the advantages of both the top-down and bottom-up approaches. In this work we systematically investigated the ordering process of polystyrene (PS) nanospheres confined inside periodic patterns with different geometries (hexagonal, linear and circular) defined by means of laser-writer lithography. The confinement of the PS nanospheres has been studied in both soft graphoepitaxy configuration (directly inside an optical resist) and hard graphoepitaxy configuration (SiO2 hard mask obtained by Reactive Ion Etching). As a result of this study, we have been able to extend the long range ordering of the PS nanospheres to areas as large as some squared millimetres.

Resume : State-of-the-art microelectronics technology produces transistors with dimensions of the order of ten nanometers. At this scale and at low temperature such devices behave as quantum dots in which a single spin can be isolated. Hole spins in silicon represent a promising direction because of limited hyperfine interaction and potentially fast manipulation. Therefore a route towards solid-state quantum computation could be to ``quantumize`` already integrated silicon bits instead of trying to scale-up existing quantum bits made with different technologies. We will present a silicon CMOS nanowire transistor operated as a hole spin qubit. Our devices are similar to industrial silicon-on-insulator transistors except that they feature two gates in series to define a double quantum dot. A microwave signal applied to one gate induces a hole spin resonance in the first dot detected via Pauli spin blockade thanks to the second dot. Pulsing the device from spin blockade to Coulomb blockade, we demonstrate coherent manipulation with Rabi frequencies as high as 80MHz with an inhomogeneous dephasing time T2*~60ns, while spin echo reveals a coherence time T2echo~250ns. Our experiment shows that industry-standard CMOS transistors can be operated as hole spin qubits with an electrical control providing fast rotation and single gate control.

Resume : Top-down processes in microelectronics allow the fabrication of structures down to ~10 nm. However, such structures are not small enough to operate at room temperature (RT) quantum devices with switching mechanisms different from CMOS. E.g., the extremely low-power device Single Electron Transistor (SET) works at RT only if the size of the quantum dot is below 5nm, and if the tunnel distances through SiO2 are a few nm only. Here we present a directed self-assembly process of a 2-3 nm small single Si dot located in the middle of a SiO2 layer with distances of ~2 nm to the upper and lower Si. The self-assembly occurs by phase separation of metastable SiOx during heat treatment. The self-assembly becomes directed by constraining and shaping the SiOx volume in such a manner that a single Si quantum dot in the requested position forms. The SiOx is fabricated by collisional mixing of Si atoms from above and below in the SiO2 layer. Two methods to form a local, constrained volume of SiOx are presented: (i) A large-area Si/SiO2/Si layer stack is irradiated with a 2nm narrow energetic Ne beam in a Helium Ion Microscope (HIM), which results in a ~10nm disk of SiOx in the buried SiO2 layer. (ii) Si pillars (<20nm) with an embedded SiO2 layer are irradiated with a broad beam of energetic Si ions. Method (ii) will be used to fabricate SETs in CMOS technology. This work has been funded by the European Union's Horizon 2020 research and innovation program under grant agreement No 688072.

Resume : Low energy ion irradiation drives surfaces out of equilibrium by continuous atomic displacements in the sub-surface. At room temperature the accumulation of the created defects leads to surface amorphization and self-organized ripple patterns perpendicular or parallel to the ion beam direction are formed for incidence angles higher than 50°. At temperatures higher than the recrystallization temperature, however, all defects in the sub-surface region are dynamically annealed and the surface remains crystalline. In this regime, ion irradiation creates vacancies and ad-atoms on the crystalline surface due to sputtering and dislocations. The surfaces morphology is now determined by the kinetics of the mobile surface species. Due to the Ehrlich-Schwoebel barrier, i.e. an additional barrier for crossing terrace steps, 3D structures are created in a “reverse epitaxy” process [1]. We will present different kinds of self-organized patterns on crystalline surfaces induced by ion irradiation at elevated temperatures. Depending on the crystalline structure and the surface orientation regular patterns of inverse pyramids with three-fold, four-fold, or six-fold symmetry are observed. Furthermore, on III-V semiconductors with zinc-blende structure extremely regular periodic groove patterns with crystalline facets are produced [2]. Such periodic patterns can be used as templates for the deposition of nanostructured thin films with effective medium properties determined by the morphology, e.g. exhibiting a strong anisotropy. [1] X. Ou, A. Keller, M. Helm, J. Fassbender, and S. Facsko, Phys. Rev. Lett. 111, 016101 (2013). [2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).