Search results for "Toe"
showing 10 items of 3824 documents
Au nanowire junction breakup through surface atom diffusion.
2018
Metallic nanowires are known to break into shorter fragments due to the Rayleigh instability mechanism. This process is strongly accelerated at elevated temperatures and can completely hinder the functioning of nanowire-based devices like e.g. transparent conductive and flexible coatings. At the same time, arranged gold nanodots have important applications in electrochemical sensors. In this paper we perform a series of annealing experiments of gold and silver nanowires and nanowire junctions at fixed temperatures 473, 673, 873 and 973 K (200 degrees C, 400 degrees C, 600 degrees C and 700 degrees C) during a time period of 10 min. We show that nanowires are especially prone to fragmentatio…
Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications
2020
AbstractThe application of molybdenum oxide in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells in the role of hole selective contact. For modeling-based optimization of such contact, knowledge of the molybdenum oxide defect density of states (DOS) is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of defects related to oxygen-vacancy and of polaron is supported by the results of our opto-electrical characterizations along with the evaluation of previous observations. As part…
Influence of Anodic and Thermal Barrier Layers on Physicochemical Behavior of Anodic TiO2 Nanotubes
2011
Electrochemical and photo-electrochemical behavior of self-organized TiO2 nanotubes formed in organic solvents have been studied by taking into account the formation of new barrier layers beneath nanotubes either due to the anodic polarization in aqueous solutions or air exposure during high temperature annealing. It has been shown that before annealing, electrochemical and photoelectrochemical answers are dominantly controlled by the physicochemical properties of the anodic barrier layer. Annealing in air at sufficiently high temperatures changes the initial amorphous structure of as-prepared nanotubes and forms a new oxide layer below them due to thermal oxidation of underneath titanium. …
THz nanocrystal acoustic vibrations from ZrO2 3D supercrystals
2013
International audience; We report sharp low-frequency Raman spectral features of supercrystals synthesized via the "benzyl alcohol route" and consisting of either yttrium-stabilized or pure zirconia (ZrO2) nanocrystals. In situ formed benzoate species control the nanocrystal growth and act as organic glue leading to the assembly of the nanocrystals in highly ordered 3D supercrystals. We attribute some Raman peaks to THz acoustic vibrations of individual nanocrystals which are only weakly coupled due to the strong acoustic mismatch between the capping ligands and the nanocrystals. Peak positions are consistent with nanocrystal sizes estimated from transmission electron microscopy and X-ray p…
Photoelectrochemical removal of chlorfenvinphos by using WO3 nanorods: Influence of annealing temperature and operation pH
2019
[EN] A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400¿°C and 600¿°C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenv…
Elaboration and characterization of barium silicate thin films.
2008
International audience; Room temperature depositions of barium on a thermal silicon oxide layer were performed in ultra high vacuum (UHV). In-situ X-ray photoelectron spectroscopy (XPS) analyses were carried out as well after exposure to air as after subsequent annealings. These analyses were ex-situ completed by secondary ion mass spectrometry (SIMS) profiles and transmission electron microscopy (TEM) cross-sectional images. The results showed that after air exposure, the barium went carbonated. Annealing at sufficient temperature permitted to decompose the carbonate to benefit of a barium silicate. The silicate layer was formed by interdiffusion of barium with the initial SiO2 layer.
Experimental and theoretical evidence for substitutional molybdenum atoms in theTiO2(110)subsurface
2006
Molybdenum was deposited at room temperature on the ${\mathrm{TiO}}_{2}(110)$ surface in the 0--1.3 equivalent monolayer (eqML) range and was then annealed at $400\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in order to reach a kind of equilibrium state. A threshold was found in the behavior of the deposit: below 0.2 eqML, substitutional molybdenum occurs in titanium sites located under the bridging oxygen atoms of the ${\mathrm{TiO}}_{2}(110)$ surface. In this position, molybdenum atoms are in a structural and chemical ${\mathrm{MoO}}_{2}$-like environment. Density-functional theory calculations show that this molybdenum site is actually the most stable one in …
A diamond (1 0 0) surface with perfect phase purity
2015
Abstract Diamond surfaces with (1 0 0) orientation and perfect phase purity regarding the coexistence of sp3 and sp2 bonding as well as near surface nitrogen implanted layers are repeatedly produced from one sample by a cycle of nitrogen implantation, etching in oxygen and wet chemical etching. Comprehensive surface studies carried out by X-ray photoelectron spectroscopy (XPS) involving a deconvolution of the C 1s peak into contributions of C sp3, C sp2 and C sp3(N) reveal the surface and near-surface phase and stoichiometry. It is demonstrated that efficient etching of nitrogen implanted diamond occurs by high temperature annealing in oxygen and a wet chemical treatment.
Efficient Vacuum-Deposited Perovskite Solar Cells with Stable Cubic FA 1– x MA x PbI 3
2020
Preparation of black formamidinium lead iodide (FAPbI3) requires high temperature annealing and the incorporation of smaller A-site cations, such as methylammonium (MA+), cesium or rubidium. A major advantage of vacuum processing is the possibility to deposit perovskite films at room temperature (RT), without any annealing step. Here we demonstrate stabilization of the cubic perovskite phase at RT, in a three-sources co-sublimation method. We found that the MA+ incorporation is a self-limiting process, where the amount of MA+ which is incorporated in the perovskite is essentially unvaried with increasing MAI deposition rate. In this way a phase-pure, cubic perovskite with a bandgap of 1.53 …
Physicochemical characterization and photoelectrochemical analysis of iron oxide films
2013
Iron oxide films with a nanoporous structure were grown by anodizing sputter-deposited Fe in a fluoride containing ethylene glycol solution and annealed under air exposure at different temperatures. X-ray diffraction and Raman spectroscopy allowed to identify the presence of hematite and/or magnetite after thermal treatment for films annealed at T ≥ 400 °C under air exposure. According to GDOES compositional depth profiles, the thermal treatment sensitively reduced the amount of fluoride species incorporated into the film during the anodizing process. A band gap value of ~2.0 eV was estimated for all the investigated layers, while a flat band potential dependent on both the growth condition…