HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. The Role of Oxygen on the Growth of Palladium Clusters Synthesized by Gas Aggregation Source William Chamorro-Coral, Amaël Caillard, Pascal Brault, Pascal Andreazza, Christophe Coutanceau, Steve Baranton

Molecular dynamics simulations are carried out for describing growth of Pd and PdO nanoclusters using the ReaxFF force field. The resulting nanocluster structures are successfully compared to those of nanoclusters experimentally grown in a gas aggregation source. The PdO structure is quasi-crystalline as revealed by high resolution transmission microscope analysis for experimental PdO nanoclusters. The role of the nanocluster temperature in the molecular dynamics simulated growth is highlighted.

ZnS:Cu films were synthetized by co-sputtering. A Cu content higher than 10.6 at% lead to changes as the shrinkage of the ZnS:Cu cell and development of a p-type behavior. These results are explained by the substitution of Zn+2 ions by Cu+ ones.

We review our recent findings that reactive magnetron sputtering can be operated without thermal assistance to produce epitaxial ZnO films and highly conductive and transparent aluminum-doped ZnO (AZO) films on large surface area. The growth of epitaxial films requires working in direct current (DC) mode at large oxygen partial pressure but high power impulse magnetron sputtering (HiPIMS) is preferred to optimize the electrical and optical properties of AZO films on large surface areas. The results are interpreted by the ability of DC sputtering to easily oxidize the target surface and the HiPIMS mode cleans and returns it to metallic during pulses. Fast oxygen atoms (ions) may be emitted in large amount using DC and bring fuel to the growing ZnO film to induce epitaxy onto sapphire. The signature of oxygen interstitials is found in DC with increasing magnitude as the oxygen content is increased in the gas phase. In contrast, the discharge voltage plays a significant role in HiPIMS to adjust the sputtering rate and clean the target surface for deposition of slightly sub-stoichiometric AZO films over the entire range of lateral positions. Thereby, transparent yet highly conductive films with resistivity in the range 4-15x10(-4) Omega m can be produced. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Nanocomposite films consisting of gold nanoparticles embedded in zinc oxide (ZnO-Au) have been synthesized with different gold loadings by reactive magnetron sputtering at near-room temperature followed by ex situ annealing in air up to 300 degrees C. Using X-ray diffraction and high resolution transmission microscopy it is shown that during deposition gold substitutes zinc in ZnO as isolated atoms and in nanoparticles still exhibiting the structure of ZnO. Both situations degrade the crystalline quality of the ZnO matrix, but thermal annealing cures it from isolated gold atoms and triggers the formation of gold nanoparticles of size higher than 3 nm, sufficient to observe a strong activation of localized surface plasmon resonance (LSPR). The amplitude of LSPR absorption observed after annealing increases with the gold loading and annealing temperature. Moreover, UV and visible photoluminescence from the ZnO matrix is strongly enhanced upon activation of LSPR showing strong coupling with the gold nanoparticles. Finally, modeling of spectroscopic ellipsometry measurements unambiguously reveals how curing the defects increases the optical bandgap of the ZnO matrix and modifies the optical dielectric functions of the nanocomposite and ZnO matrix.

We present the growth of In2S3 onto Cu3BiS3 layers and soda-lime glass (SLG) substrates by using chemical bath deposition (CBD) and physical co-evaporation. The results reveal that the microstructure and the optical properties of the In2S3 films are highly dependent on the growth method. X-ray diffractrograms show that In2S3 films have a higher crystallinity when growing by co-evaporation than by CBD. In2S3 thin films grown by CBD with a thickness below 170 nm have an amorphous structure however when increasing the thickness the films exhibit two diffraction peaks associated to the (1 0 3) and (1 0 7) planes of the beta-In2S3 tetragonal structure. It was also found that the In2S3 films present an energy bandgap (E-g) of about 2.75 eV, regardless of the thickness of the samples. (C) 2015 Elsevier B.V. All rights reserved.

A new effective medium theory is introduced to describe the optical properties of a two-dimensional array of metallic nanoislands. This model which takes into account both the nanoisland orientation and their shape distribution is successfully used to interpret the ellipsometric measurements performed on gold nanoislands sputtered on a silicon substrate. By coupling ellipsometry to atomic force microscopy measurements, we show that the growth mechanism involves a Volmer-Weber growth mode. The optical anisotropy of uniaxial films was attributed to in-plane preferential self-orientation of gold nanoislands. Finally, we demonstrate that the optical birefringence and dichroism of nanoisland layers can be tuned during the film growth and are due to the splitting of the plasmon resonance into two modes: the transversal and the longitudinal modes of gold nanoislands.

La búsqueda de fuentes de energía alternativas a los combustibles fósiles ha permitido el desarrollo y uso de diferentes tecnologías basadas en el uso de la energía solar. Las celdas solares basadas en compuestos organicos ofrecen grandes ventajas en aspectos económicos, ambientales y tecnológicos y es por eso que la evolución que ha tenido desde sus comienzos ha permitido su paso hacia la producción a mediana escala por lo que sus perspectivas de crecimiento son muy alentadoras.

Single-domain epitaxial ZnO films are grown near-room temperature (below 40 degrees C) on (0 0 0 1)-sapphire using reactive magnetron sputtering of a zinc target in the transition between the metallic and compound sputtering regimes. As the oxygen content in the reactive gas mixture is increased, the in-plane six-fold symmetry of hexagonal wurtzite ZnO, probed by phi-scan measurements, develops. Transmission electron microscopy analyses confirm that single-domain epitaxial layers are formed. This is accompanied by the incorporation of oxygen interstitial defects associated with oxygen over-stoichiometry and by compressive stresses. A model is proposed to explain the observed behaviour based on the transformation of the kinetic energy of fast oxygen particles into the mobility of the adatoms.

800x600 Normal 0 21 false false false ES-CO X-NONE X-NONE En este trabajo se evaluo el efecto del recocido en atmosfera inerte sobre las propiedades opticas, morfologicas y estructurales de peliculas delgadas de poli(3-hexiltiofeno) (p3HT), metil ester del acido fenil-C61-butirico (PCBM) y mezcla (p3HT :PCBM), crecidas sobre sustratos de vidrio alcalino mediante spin coating, variando la temperatura de recocido entre 80 y 160°C y el tiempo de recocido entre 0 y 45 minutos. La evaluacion de las propiedades se realizo a traves de medidas de absorbancia, difraccion de rayos-x (DRX) y microscopia de fluorescencia. El estudio permitio encontrar condiciones de recocido optimas (120°C, 30min) requeridas para la preparacion de mezclas de PCBM:p3HT con propiedades adecuadas para ser usadas como capa activa en celdas solares organicas con estructura tipo bulk heterojunction. Muestras preparadas bajo estas condiciones presentan crecimiento preferencial a lo largo del plano (001) con alto grado de ordenamiento cristalografico, alta absorcion en el visible y alta densidad de interfaces PCBM/p3HT. Imagenes tomadas con microscopia de fluorescencia permitieron estudiar el efecto de la temperatura y tiempo de recocido sobre la luminescencia de la mezcla (p3HT :PCBM) y sus componentes e identificar la formacion de fibras micrometricas de PCBM a temperaturas de recocido mayores a 120°C.

ZnS thin films were deposited by CBD (chemical bath deposition) method using a solution containing thiourea and zinc acetate as sources of S and Zn and ammonium citrate as complexing agent. The samples were grown on soda lime glass substrates covered with a Cu2SnZnS4(CZTS) thin film. Through an extensive parameter study carried out varying the main deposition parameter in a wide range, conditions were found to grow ZnS thin films with suitable properties to be used as buffer layer in Cu2SnZnS4 based solar cells.The ZnS films were characterized using techniques such as spectrofotometry, X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD measurements revealed that ZnS films with thicknesses lower than200 nm grow with amorphous structure; however, samples with thicknesses higher than3 nm present crystalline structure corresponding to the ZnSO8H8 (zinc sulphohydroxide) phase, indicating that the film formed is really a mixture of ZnS and Zn hydroxides, known generically in the literature as Zn(S,OH).

Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.