Showing papers on "Chemical state published in 1984"
TL;DR: The surface of a typical CuO/ZnO/Al/sub 2/O/sub 3/ methanol consists of metallic Cu and ZnO during actual reaction conditions as mentioned in this paper.
124 citations
TL;DR: In this article, a 1 atm of flowing hydrogen and then examined by ESCA, it was shown that the Group VIII metal is present in a metallic state in the reduced catalyst and that the majority of the tin is in a valence state higher than Sn(0).
95 citations
TL;DR: The surface chemistry and stoichiometry of p and n-type CdTe photoelectrodes treated with oxidizing and reducing etches have been characterized by x-ray photoelectron and Auger electron spectroscopies as discussed by the authors.
Abstract: The surface chemistry and stoichiometry of p‐ and n‐type CdTe photoelectrodes treated with oxidizing and reducing etches have been characterized by x‐ray photoelectron and Auger electron spectroscopies. The results of surface analysis have been correlated with the photoelectrochemical and capacitance–potential behavior of the photoelectrodes. ‘‘Oxidized’’ surfaces are covered by a thin Te0/TeO2 layer (or a thicker Te0 layer, if the etching procedure is slightly altered), resulting in Fermi level pinning: a constant photovoltage is found for a wide range of redox potentials and potential‐independent space charge layer capacitance obtains. ‘‘Reduced’’ surfaces closely resemble ion sputtered CdTe in chemical state and stoichiometry, resulting in more nearly ‘‘ideal’’ behavior: the semiconductor/electrolyte interface is rectifying in the dark; capacitance–potential behavior follows the Mott–Schottky equation near flat band conditions; and photovoltage varies with redox potential, from 0 to ∼0.7 V for p‐CdTe.
82 citations
TL;DR: The atomic ratio of hydrogen to carbon was approximately 0.2 at the film surface and rose to approximately 1.0 at a depth of 500 A. The chemical state of non-bonded hydrogen was not determined; however, the effective diffusion coefficient computed from the hydrogen depth profile was extremely low as mentioned in this paper.
75 citations
TL;DR: A review of the use of static secondary ion mass spectrometers (SSIMS) and fast atom bombardment (FABMS) in applied surface analysis can be found in this article.
Abstract: A review is presented of the use of static secondary ion mass spectrometry (SSIMS) and fast atom bombardment mass spectrometry (FABMS) in applied surface analysis. Some common criticisms of SIMS are discussed first, and then the experimental apparatus required is described briefly. Four main areas of application have been chosen: catalysts, polymers, glasses and metals, to illustrate the power of SSIMS/FABMS in characterising the chemical state of material surfaces. Finally the very new technique of SSIMS imaging has been described and some preliminary results presented, to indicate its potential in obtaining chemical state information at high spatial resolution.
73 citations
TL;DR: In this article, X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA), and chemical analysis of molybdenum supported on Al2O3, SiO2, CeO2 and carbon were examined in calcined, reduced, and sulfided states using O2 adsorption, XRD and ESCA data.
45 citations
TL;DR: In this article, the chemical states of iron compounds produced on a steel surface in SO 2 (0.16 vol%) environment were investigated non-destructively and the formation of FeSO 4 · H 2 O as the initial, FeSO4 ·4H 2O as the intermediate and γ-FeOOH as the final corrosion product was confirmed by analysis of CEM spectra.
36 citations
TL;DR: In this paper, the surface recoiling (SR) technique using a pulsed 3 keV Ar+ source and time-of-flight detection of both neutrals and ions is demonstrated to have outer monolayer sensitivity and the capability of directly detecting adsorbate hydrogen.
30 citations
TL;DR: An experimental system for studying surface reactions in the process of microwave plasma etching has been developed in this paper, where a surface etched in the microwave plasma can be analyzed with x-ray photoemission spectroscopy (XPS) without exposure of the surface to room air.
Abstract: An experimental system for studying surface reactions in the process of microwave plasma etching has been developed. In the system, a surface etched in the microwave plasma can be analyzed with x‐ray photoemission spectroscopy (XPS) without exposure of the surface to room air. In addition, we have developed a procedure for calculating a thickness of a surface layer stoichiometrically different from the substrate material and densities of atoms in the layer. Chemical changes in etched Si and SiO2 surfaces caused by exposing these surfaces to room air are investigated with XPS to show the utility of the system. When the surfaces etched in SF6 microwave plasma are exposed to room air, the chemical states of the surfaces change rapidly. This is mainly due to surface oxidation and adsorption of hydrocarbon compounds to the surfaces. The rapid changes are more clearly shown from increases in surface layer thickness and the number of O and C atoms in the layer. It is clarified that exposure of etched surface to room air causes the serious disturbance, and that accurate information can not be obtained any longer. The present system which eliminates this disturbance allows accurate measurement of surfaces for detailed investigation of the surface reaction in microwave plasma etching.
29 citations
TL;DR: In this article, an analytical study of the oxidation behavior of Fe72Cr23Al5 alloy in relation to the microstructure, particularly carbon and sulphur localization and chemical state, indicates that these elements have a strong influence on alumina growth and adherence.
Abstract: Kinetic and analytical study of oxidation behaviour of Fe72Cr23Al5 alloy in relation to the microstructure, particularly carbon and sulphur localization and chemical state, indicates that these elements have a strong influence on alumina growth and adherence. Competition between oxidation and a carbide precipitation slightly increases the oxidation rate during isothermal treatments but has a beneficial influence on the oxide scale adherence. Sulphide precipitation in the metallic substrate has a disastrous effect on oxidation: large weight gains are observed, due to internal oxidation at sulphides and presence of sulphur in the alumina. Moreover, it was confirmed that alumina growth is controlled by preferential oxygen diffusion along short-circuit paths.
25 citations
TL;DR: The surface chemical composition of ash particles collected in the electrostatic precipitator of a power plant burning high sulfur coal was determined by using X-ray photoelectron spectroscopy (XPS).
Abstract: The surface chemical composition of ash particles collected in the electrostatic precipitator of a power plant burning high sulfur coal was determined by using X-ray photoelectron spectroscopy (XPS). A bulk particle sample was separated into magnetic and nonmagnetic fractions for comparison to the unfractionated sample. After XPS characterization, the samples were subjected to rare gas ion (Ar/sup +/) sputtering to remove surface material. The XPS technique then was used to detect any sputter-induced composition changes. These results were compared with data obtained by heating similar samples under high vacuum and recording XPS data as a function of temperature (20-200/sup 0/C). Effects of sample temperature on the extent of differential charging phenomena influencing XPS photopeaks and chemical state information also were documented.
TL;DR: In this paper, the authors used transmission electron microscopy to bring evidence for an alternation in the shape of iron crystallites supported on planar, nonporous, alumina substrates when the specimens were heated, at 400 °C, in hydrogen contaminated with traces of oxygen (less than 1 ppm) and/or moisture.
TL;DR: In this paper, a core-level X-ray photoelectron spectra measurement has been performed for native oxide of single crystal GaAs wafer and proved to be a useful method for obtaining chemical state depth profile near the surface.
Abstract: Angular dependent core-level X-ray photoelectron spectra measurement has been performed for native oxide of single crystal GaAs wafer and proved to be a useful method for obtaining chemical state depth profile near the surface. Metallic arsenic is buried in a growing native oxide layer and stranded at the interface layer of oxide and GaAs substrate.
TL;DR: In this paper, the oxide structure was studied by RBS (Rutherford backscattering spectrometry) and XPS (X-ray photoelectron spectroscopy) techniques and the correlation between photocharacteristics and its oxide structure is discussed.
TL;DR: In this article, the phosphorus-, sulfur-, and chlorine-L2,3 emission spectra in various compounds were obtained using secondary excitation and discussed from the point of view of chemical-state analysis.
Abstract: The phosphorus-, sulfur-, and chlorine-L2,3 emission spectra in various compounds are obtained using secondary excitation. The spectra are discussed from the point of view of chemical-state analysis. It should be noted that the spectra of a highly ionic bond reveal scarcely no influence of the cations. However, the spectra with a covalent character are complex as a result of the molecular orbital generated with the covalent bond. The spectral features are influenced by the chemical condition of the surrounding atoms and are sensitive to oxygen and hydrogen.
TL;DR: In this article, the X-ray photoelectron spectra of HCl oxides grown at 1100°C with 10 vol.% HCl were analyzed and the results support the view that chlorine exists in a separate phase within SiO2.
TL;DR: In this article, a quantitative approach to AES is illustrated for various metal-sulfur compounds involving: (a) intensity measurements via integral areas of background subtracted N(E) spectra (including sample probe potential biasing to improve background subtraction); (b) low primary electron dose, pulse-count spectrum acquisition to minimize primary electron beam damage and charging artifacts; (c) corrections to spectral intensity for variations in electron backscattering and inelastic Auger electron mean free path for each metal sulfate compound matrix; XPS quantitative analysis to correct for differences in surface
Abstract: A quantitative approach to AES is illustrated for various metal–sulfur compounds involving: (a) intensity measurements via integral areas of background subtracted N(E) spectra (including sample probe potential biasing to improve background subtraction); (b) low primary electron dose, pulse-count spectrum acquisition to minimize primary electron beam damage and charging artifacts; (c) corrections to spectral intensity for variations in electron backscattering and inelastic Auger electron mean free path for each metal–sulfur compound matrix; (d) XPS quantitative analysis to correct for differences in surface vs. bulk stoichiometries. Although the above approach results in improved analytical precisions, a residual difference of greater than a factor of 2 remains in the Auger elemental sensitivity factor for sulfur (LMM) in corresponding metal sulfate vs. sulfide compounds. This suggests a chemical state dependent Auger electron yield (core level ionization cross section times the Auger transition probability). Accurate AES quantification, therefore, may require chemical state specific sensitivity factors, particularly for valence shell transitions.
TL;DR: In this paper, the chemical states of 35S in solutions of thermal neutron irradiated (TNI) chloride samples have been investigated using chemical precipitation techniques after sample dissolution in the presence or absence of inactive carriers in the forms of S2-, so32-, s04'- and SZO~~-, and anion exchange separation.
Abstract: The chemical states of 35S in solutions of thermal neutron irradiated (TNI) chloride samples have been investigated using (a) chemical precipitation techniques after sample dissolution in the presence or absence of inactive carriers in the forms of S2-, so32-, s04'- and SZO~~-, and (b) anion exchange separation. The second method has been used to study variations in the composition of TNI chloride solutions as a function of the time interval between sample dissolution and addition of the solution to the ion exchange column. The results point towards the following conclusions: (i) dissolution of TNI chloride in water or 0.3 M NaOH in the absence of any inactive sulfur-anion carrier yields primarily 35S032- and not 35S042- and 35S2- as was thought earlier; (ii) about 20% of the 35s in solution is present initially as elemental sulfur; (iii) the composition of the solution varies markedly with time; (iv) in the presence of carrier sulfur anions at the time of dissolution different 35S-species are formed; and (v) chemical precipitation techniques do not give a true indication of the species present in solution.
01 Jan 1984
TL;DR: In this article, the interrelations of the sputtering and the changes of surface states were investigated experimentally for the studies of the surface properties of solids and the measurement of the depth profile of an element.
Abstract: For the studies of the surface properties of solids and the measurement of the depth profile of an element, ion beam sputtering has been used generally in combination with various methods for surface analysis, e.g. secondary ion mass spectrometry(SIMS). However, it has not been investigated experimentally about the interrelations of the sputtering and the changes of surface states.[1]
TL;DR: In this paper, the x-ray intensities of the Kβ and KO lines relative to the Kα1, transition were measured with high accuracy for the pairs La2O3-La, SmS-Sm, Sm2O 3-Sm and Ta2O5-Ta.
Abstract: The x-ray intensities of the Kβ and KO lines relative to the Kα1, transition were measured with high accuracy for the pairs La2O3-La, SmS-Sm, Sm2O3-Sm and Ta2O5-Ta. The Kβ13 and Kβ24 lines do not show significant intensity shifts. However, the intensity of the KO line is in La2O3 (15.0 ±4.7)% higher, in SmS (6.9 ± 2.7)% lower and in Ta2O5 (12.5 ± 8.7)% higher than that emitted from the corresponding metal. These results can be reproduced by Dirac-Fock-calculations, where the KO-intensities show a typical dependence on the quantum numbers of the valence electrons. The observed shifts indicate a 4f-5d hybridization or promotion in metallic Lanthanum and suggest the missing of a 4f electron in metallic Samarium compared to the free atom.
TL;DR: In this article, focused ion beam sputtering was developed in a laboratory for actinide target preparations as this technique allows the use of only milligrams of starting material. But it does not take into account the radioactivity of the actinides and the fact that some isotopes are scarce.
01 Jan 1984
IBM1
TL;DR: In this paper, a model based on the tunneling of electrons between the surface and the sputtered atom has been proposed to explain the work function dependence of the ionization probability, provided that the external atom used to induce the work-function change does not affect the chemical state of the target atoms.
Abstract: It has been observed in many systems that lowering of the work function Ф of the sample surface enhances the formation of negative secondary ions [1, 2] while suppressing the formation of positive ions [3]. A model based on the tunneling of electrons between the surface and the sputtered atom has been proposed [3,4,5] to explain these results. According to the model, the work-function dependence of the ionization probability should be independent of how the work-function change ΔФ is being induced, provided that the external atom used to induce ΔФ does not affect the chemical state of the target atoms. We have tested this prediction by studying the emission of secondary ions from Si(111) surfaces using Cs and Li overlayers to induce changes in Ф. These systems are chosen because the adsorption of Cs and Li does not change the chemical state of the surface Si atoms in any appreciable way.
01 Jan 1984
TL;DR: Several transition metal substrates and steel specimens were ion-implanted with various species including nitrogen, chromium, and titanium at doses from 1016 to 1018 atoms/cm2 as discussed by the authors.
Abstract: Several transition metal substrates and steel specimens were ion-implanted with various species including nitrogen, chromium, and titanium at doses from 1016 to 1018 atoms/cm2. The purpose of the implantation study was to modify the surfaces of the materials in order to improve their resistance to wear, fatigue, and corrosion [1,2].