Investigation of vanadium and nitride alloys thin layers deposited by PVD

Lien vers la version éditeur: http://dx.doi.org/10.1051/epjconf/20122900042In this work we present the technique of magnetron vapor deposition and the effect of several deposition parameters on the structural and morphological properties of prepared thin films. It was noted that the deposition time has an effect on the crystallinity, mechanical properties such as residual stress, roughness surface and the layer composition from target products. Studies were carried out on layers of vanadium (V) and the nitride vanadium (VN)

Correlation between physical properties and growth mechanism of In

Indium sulfide (In2S3) thin films were grown on ITO-coated glass substrate using the electrodeposition method. The effect of the deposition time on the structural, morphological, optical and electrical properties of the as-grown In2S3 thin films was studied. XRD spectra of the obtained films reveal the polycrystalline nature of (β-In2S3) with a tetragonal crystal structure along the (109) plane, and exhibit a sharp transition to the (0012) plane when the deposition time is extended beyond 20 min. Using atomic force microscope (AFM), the surface morphology shows a remarkable change in the grain size, thickness, and surface roughness when varying the deposition time. UV-VIS spectrophotometer show that the optical band gap values of In2S3 decrease from about 2.82 to 1.93 eV by extending the electrodeposition duration from 5 to 20 min. All films were found to have an n-type character with a lower electrical resistivity of about 1.8×10-3 Ω cm for films deposited at 20 min

Photoelectrochemical properties of nanocrystalline ZnS discrete versus continuous coating of ZnO nanorods prepared by electrodeposition

International audienceWe developed nanostructured photoanodes for photoelectrochemical (PEC) water splitting and hydrogen generation. They are based on ZnO nanorods electrodeposited on conductive ITO glass on which ZnO@ZnS heterojunctions were formed using two different approaches. In the first case, the ZnO nanorods were sulfided by a prolonged contact with Na2S aqueous solution, while in the second one, they were immersed in an alcoholic solution of 2 nm sized polyol-made ZnS quantum dots (QDs). Transmission electron microscopy showed that a continuous thin layer of ZnS is formed around ZnO leading to a core@shell structure in the first case, while discrete QD aggregates were grafted at the surface of these rods leading to a kind of tologyin, in the second case. PEC properties of both composite films were measured, using a home-made electrochemical cell and illuminating the anodes with a Xenon lamp. A net enhancement of the photocurrent was observed when the ZnS coating was processed, suggesting a low carrier recombination rate, a higher efficiency toward water oxidation, and then electron transfer to the used cathode (Pt wire) for H+ reduction and H2 generation. Interestingly, the performances of the two composite films were found to be comparable, suggesting that a discrete coating of the ZnO nanorods by a small amount of preformed ZnS QDs is enough to improve their properties for the desired application

The structural and the photoelectrochemical properties of ZnO–ZnS/ITO 1D hetero-junctions prepared by tandem electrodeposition and surface sulfidation: on the material processing limits

International audienceZnO–ZnS 1D hetero-nanostructures were prepared by an easy and scalable processing route. It consists of ZnO nanorod electrodeposition on ITO substrate and surface sulfidation by ion exchange in an aqueous Na 2 S solution. Increasing the treatment contact time (t c) from 8 to 48 h involves different ZnS growth mechanisms leading to different structural and microstructural rod characteristics, even if the overall size does not change significantly. Grazing X-ray diffraction, high-resolution microscopy, energy-dispersive spectrometry and X-ray photoelectron spectroscopy describe the outer surface layer as a poly-and nanocrystalline ZnS blende shell whose thickness and roughness increase with t c. The ZnO wurtzite–ZnS blende interface goes from continuous and dense, at short t c , to discontinuous and porous at long t c , indicating that ZnS formation proceeds in a more complex way than a simple S 2À /O 2À ion exchange over the treatment time. This feature has significant consequences for the photoelectrochemical performance of these materials when they are used as photoanodes in a typical light-assisted water splitting experiment. A photocurrent (J p) fluctuation of 45% for less than 5 min of operation is observed for the sample prepared with a long sulfidation time while it does not exceed 15% for that obtained with a short one, underlining the importance of the material processing conditions on the preparation of valuable photoanodes