Improvement of the photocatalytic degradation property of atomic layer deposited ZnO thin films: the interplay between film properties and functional performances:

In this work, we have evidenced the impact of stoichiometry on the photocatalytic properties of ZnO nanofilms grown by atomic layer deposition (ALD). We point out the importance of hydrogen incorporation and propose here a model explaining the presence of Zn-OH impurities in the form of a ZnOxHy amorphous matrix hosting ZnO crystallites. We evidence that this phase prevails in films grown at low temperatures and prevents the photoluminescence and photocatalytic activity of ZnO films. We also point out that high temperature ALD processes promote the preferential growth of ZnO films in the (002) orientation, leading to a significant increase of the film wettability and so their photocatalytic degradation performances

Recent progress and perspectives of space electric propulsion systems based on smart nanomaterials

Miniaturized spacecraft built from advanced nanomaterials are poised for unmanned space exploration. In this review, the authors examine the integration of nanotechnology in electric propulsion systems and propose the concept of self-healing and adaptive thrusters

CVD of Ru, Pt and Pt-based alloy thin films using ethanol as mild reducing agent

3 Premkumar, P. Antony Prakash, N. S. Gaillard, F. Bahlawane, N.Noble metal thin films (Pt and Ru) were grown at 250 degrees C, using commercially available precursors, by the pulsed spray evaporation chemical vapor deposition (PSE-CVD) technique. The growth process relies on the thermally activated reaction of ethanol with the metal acetylacetonate precursors. The synthesized polycrystalline films are pure metal phase and crystallize in hexagonal (Ru) and cubic (Pt) structures. The formation of an interfacial suicide phase was noticed in the case of the Pt growth on silicon substrates. The films are smooth, continuous and show a steady growth without any noticeable incubation time. The single-step growth of Pt-based alloys, Pt-Co and Pt-Cu, with controlled composition was performed by simply adjusting the composition of the liquid feedstock. (C) 2010 Elsevier B.V. All rights reserved

Apport des techniques XRFS et LEEIXS à l'étude de la formation de films de silice sur acier par PACVD

Deux méthodes d'émission X (XRFS et LEEIXS) ont été utilisées pour caractériser des films minces organosilanés déposés par "polymérisation plasma" (procédé PACVD) sur des substrats d'acier inoxydable. Les mesures d'épaisseur ont été réalisées par XRFS et les déterminations de variation de composition ou d'effets chimiques en fonction de divers paramètres expérimentaux ont été effectuées par LEEIXS. Cette dernière méthode, très sensible à la détection des éléments légers, a permis d'optimiser les conditions d'élaboration pour obtenir des dépôts de silice pure.Organosilane thin films deposited by "plasma polymerization" (PACVD process) on stainless steel substrates have been investigated by two x-ray emission methods (XRFS and LEEIXS). Thickness measurement was performed by XRFS and composition or chemical effect variations were determined by LEEIXS as a function of various experimental parameters. The latter method, very sensitive to the detection of light elements, has allowed to optimize the deposition conditions and to obtain pure silica films

CVD of Ru, Pt and Pt-based alloy thin films using ethanol as mild reducing agent

Premkumar PA, Prakash NS, Gaillard F, Bahlawane N. CVD of Ru, Pt and Pt-based alloy thin films using ethanol as mild reducing agent. MATERIALS CHEMISTRY AND PHYSICS. 2011;125(3):757-762.Noble metal thin films (Pt and Ru) were grown at 250 degrees C, using commercially available precursors, by the pulsed spray evaporation chemical vapor deposition (PSE-CVD) technique. The growth process relies on the thermally activated reaction of ethanol with the metal acetylacetonate precursors. The synthesized polycrystalline films are pure metal phase and crystallize in hexagonal (Ru) and cubic (Pt) structures. The formation of an interfacial suicide phase was noticed in the case of the Pt growth on silicon substrates. The films are smooth, continuous and show a steady growth without any noticeable incubation time. The single-step growth of Pt-based alloys, Pt-Co and Pt-Cu, with controlled composition was performed by simply adjusting the composition of the liquid feedstock. (C) 2010 Elsevier B.V. All rights reserved

Broadband characterization of congruent lithium niobate from mHz to optical frequencies

Lithium niobate (LiNbO3) is a well known uniaxial ferroelectric material. Using impedance measurement, quasi-optical free-space characterization, THz time domain spectroscopy (THz-TDS) and ellipsometry, its dielectric permittivity/refractive index was characterized depending on the crystal orientation over a broad frequency range: 1 mHz to 1 PHz (lambda = 300 nm). Three different frequency ranges, separated by well identified resonances, are observed: low frequency \u27free-piezoelectric\u27 response, intermediate frequency \u27clamped-ionic\u27 response and high frequency \u27electronic\u27 response. These features are discussed with an emphasis on the role of the crystallographic structure and piezoelectric response

Thermoresponsive Black VO₂-Carbon Nanotubes Composite Coatings for Solar Energy Harvesting

Solar energy harvesting is an essential component for a clean and sustainable future energy supply. Hereby, solar–thermal energy conversion is of a significant importance, and the role of absorbing layers is pivotal. Nanoscale design of thermally responsive absorbing nanocomposite coatings is addressed in this study with the objective to tailor the light absorption behavior. While carbon nanotubes (CNTs) act as perfect black absorbers, vanadium dioxide (VO2) shows a semiconductor-to-metal transition (SMT) at 67 °C with an abrupt change in the optical properties. Combining the properties of these two nanometric building blocks is investigated as an approach to design smart black nanocomposite films. The CNTs feature either an upward or a downward thermal emissivity switching across the SMT depending on the morphology of the overgrown VO2 nanolayer. Decorated CNTs with VO2 nanoparticles feature an enhancement of the thermal emissivity above the SMT, whereas VO2-covered CNTs feature a decrease of thermal emissivity when they turn metallic above the SMT. The results were successfully explained by a theoretical model based on effective media approximations. By means of this model, the percolation threshold for the VO2 inclusions was identified. VO2 inclusions below this threshold are mostly confined in small domains, and near/mid-infrared light absorption dominates in the metallic phase as a consequence of the localized surface plasmons’ excitation. Above the percolation threshold, VO2 inclusions form large continuous domains that are more reflective in the metallic phase. The percolation threshold is the result of surface-energy-driven dewetting that can be influenced by the implemented thermal treatment. The developed VO2–CNT nanocomposite films hold appealing properties for the design of smart absorbers for solar energy harvesting and thermal management as well as photothermal actuators