Search results for "Surfaces"
showing 10 items of 2837 documents
Why are hydrogen ions best for MeV ion beam lithography?
2013
The exposure characteristics of poly-(methyl methacrylate) (PMMA) for 2MeV ^1H^+, 3MeV ^4He^2^+ and 6MeV ^1^2C^3^+ have been investigated. The samples were characterised using Atomic Force Microscopy (AFM), optical microscopy and Raman spectroscopy. Development was carried out using a 7:3 propan-2-ol:H"2O mixture to determine clearing and cross-linking fluences. It was found that protons had a considerably wider tolerance to exposure variations and a smaller span of doses within the ion track. Furthermore, the void formation and consequent stress-induced surface roughening were smaller for protons. For all ions, the C?C bond Raman signal increased continuously with dose and fluence, even we…
Properties of AlN grown by plasma enhanced atomic layer deposition
2011
Abstract The influence of growth parameters on the properties of AlN films fabricated by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia precursors was investigated. The atomic concentrations, refractive index, mass density, crystallinity and surface roughness were studied from the films grown in the temperature range of 100–300 °C with plasma discharge times between 2.5 and 30 s. The AlN films were shown to be hydrogen rich having H concentrations in the range of 13–27 at.% with inverse dependence on the growth temperature. The carbon and oxygen concentrations in the films were less than 2.6% and 0.2%, respectively. The refractive index and mass density of the f…
Dual Ni/Ni-Co electrodeposited coatings for improved erosion-corrosion behaviour
2019
Abstract Industrial applications of hydrophobic metallic coatings are limited to durability of their surface structures against detrimental effects of the surrounding environments. In the present research, the life-long of the hierarchical structure of hydrophobic nickel coating in an erosive-corrosive solution was investigated. The effect of alloying with cobalt on strengthening the hierarchical structures was also investigated. In this regard, highly hydrophobic Ni/Ni, Ni-Co/Ni-Co, dual Ni/Ni-Co and dual Ni-Co/Ni coatings with rough hierarchical structures were electrodeposited. In situ electrochemical measurements were performed to investigate changes in corrosion resistance and hydropho…
Modulation of the organic heterojunction behavior, from electrografting to enhanced sensing properties
2019
International audience; The energy barrier of an organic heterojunction built on ITO electrodes and made from a low conductive sublayer (Cu(F16Pc)) covered by a highly conductive semiconductor (LuPc2) is modulated by electrografting of organic layers before depositing the sublayer. Impedance spectroscopy clearly demonstrates the increase of the energy barrier at the ITO – sublayer interface. Additionally, the electrografting is a versatile and promising method for the tuning of heterojunctions. The I(V) characteristics of the heterojunctions are highly modified by the electrografting. The same electromodifications of electrodes carried out on LuPc2 resistors lead to a modification of their …
Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation
2015
Abstract A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp 3 bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp 3 percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not…
Quantifying the Composition of Methylammonium Lead Iodide Perovskite Thin Films with Infrared Spectroscopy
2019
Lead halide perovskites (ABX3) are generally formed from a reaction of the lead halide salt (BX2) with the halide salt of the A cation (AX). The effects of varying film compositions as result of non-stoichiometric precursor ratios on electronic properties of halide perovskites are currently under debate. It is imperative, but experimentally challenging, to determine the chemical composition of thin films as a function of precursor ratio for a full understanding of the effect. Herein we report a precise quantification of the methylammonium (MA) content in differently fabricated films of MAPbI3 via infrared (IR) spectroscopy. We compare the thin film data to the first high quality dielectric …
Electrochemical Impedance Spectroscopy of Polyelectrolyte Multilayer Modified Electrodes
2004
Electrochemical impedance spectroscopy, Fourier transform infrared reflection−absorption spectroscopy, and cyclic voltammetry were employed to characterize polyelectrolyte multilayers (PEMs) fabricated with poly(styrenesulfonate) as the polyanion and the polypeptides poly-l-histidine, poly-l-lysine, and poly-l-arginine as polycations. The layer-by-layer electrostatic assembly was produced onto alkanethiol-modified gold surfaces. The frequency response reveals that the effect of the number of layers seems to be related to a progressive reduction in the active area of the PEM-modified electrodes. The active area after the deposition of seven layers can be lower than 10% of its original value.…
Reagent free electrochemical-based detection of silver ions at interdigitated microelectrodes using in-situ pH control
2021
Abstract Herein we report on the development of an electrochemical sensor for silver ions detection in tap water using anodic sweep voltammetry with in-situ pH control; enabled by closely spaced interdigitated electrode arrays. The in-situ pH control approach allowed the pH of a test solution to be tailored to pH 3 (experimentally determined as the optimal pH) by applying 1.65 V to a protonator electrode with the subsequent production of protons, arising from water electrolysis, dropping the local pH value. Using this approach, an initial proof-of-concept study for silver detection in sodium acetate was undertaken where 1.25 V was applied during deposition (to compensate for oxygen producti…
XPS study of pumice-supported palladium and platinum catalysts
1992
An XPS study has been performed on samples of monometallic of palladium and platinum and on bimetallic Pd-Pt catalysts supported on pumice. A negative shift of about 0.5 eV in the Pd 3d and Pt 4f binding energies of the catalysis relative to the energies of the same levels in the pure metals suggested an increase in the electron density in both metals. A quantitative XPS analysis indicated that the supported metals did not modify the surface atomic composition of pumice
Compaction of tungsten oxide films by ion-beam irradiation
1993
Abstract Evaporated amorphous tungsten oxide films with low densities, deposited on different substrates, have been irradiated with various types of ions of different energies up to 30 MeV, and with fluences up to 10 18 cm −2 . Compaction of the films up to nearly the bulk density was observed. No changes of the stoichiometry as determined by various ion-beam analysis techniques were detectable. Raman measurements showed that ion-beam-modified films are also amorphous, but have a different microstructure from as-deposited films. The irradiated films have a higher refractive index than the as-deposited films. A low threshold for the compaction effect of a few times 10 12 ions cm −2 was found…