Showing papers on "Chemical state published in 1983"
TL;DR: In this paper, the compositions of these sputtered thin films were analyzed by the electron microprobe; the Bi2Te3 film showed non-stoichiometric compositions of Bi=44.5 at.%, Te=55.1 at., and PbTe films were stoichiometric.
Abstract: Thin films of Bi2Te3 and PbTe were produced by sputtering using targets of stoichiometric compounds. The compositions of these sputtered thin films were analyzed by the electron microprobe; the Bi2Te3 film showed nonstoichiometric compositions of Bi=44.5 at.%, Te=55.5 at.%, whereas the compositions of PbTe films were stoichiometric. The morphology of these sputtered films was established to be polycrystalline by x‐ray diffraction (XRD). XRD peaks of Bi2Te3 films revealed the existence of nonstoichiometric crystalline phases; PbTe films have a single cubic phase with (200) preferred orientation. X‐ray photoelectron spectroscopy chemical state analysis on both Bi2Te3 and PbTe films showed that Bi, Pb, and Te have one chemical state consistent with the valence state in the compounds. Room temperature carrier concentration and Hall mobility of BiTe3 film were measured to be 7.2×1020 cm−3 and 15 cm2/V‐s respectively; the corresponding values of PbTe films are 5.6×1019 cm−3 and 38 cm2/V‐s, respectively. Doping ...
53 citations
TL;DR: In this article, a monochromatization of Ag Lα X-rays is achieved by fitting an Ag anode to a conventional Al Kα monochromeator, where the 1s and KLL Auger series from Al to Cl are generated by this high energy source.
Abstract: Monochromatization of Ag Lα X-rays is achieved by fitting an Ag anode to a conventional Al Kα monochromator. Many new XPS lines are generated by this high energy source including the 1s and KLL Auger series from Al to Cl. Chemical state determination by means of the Auger parameter for these elements is greatly assisted by the reduced X–ray linewidth after monochromatization. Three glass fibre samples with different surface pre-treatments were studied to show that chemical state information could be extracted from even these complex, rough and insulating surfaces by using this novel X-ray source.
36 citations
TL;DR: The surface properties of ZrMn 2 and TiMn2−x (x = 0, 0.5) were investigated using X-ray photoelectron spectroscopy because of the readiness of hydrogen sorption of many AB 2 compounds as mentioned in this paper.
Abstract: The surface properties of ZrMn 2 and TiMn 2−x ( x = 0, 0.5) were investigated using X-ray photoelectron spectroscopy because of the readiness of hydrogen sorption of many AB 2 compounds. The concentration of the components and their chemical state were analysed in samples which had been fractured in an ultrahigh vacuum, exposed to increasing doses of oxygen and air and subjected to hydrogen absorption and desorption. It is concluded that surface segregation accounts for the ease with which hydrogen is absorbed. Manganese, but not zirconium or titanium, segregates and is preferentially oxidized. Zirconium and titanium are assumed to form metallic precipitates on the subsurface below the oxidized manganese. The precipitates and the subsurface can catalyse the H 2 2H reaction. Furthermore the precipitates themselves may form hydrides and spill over atomic hydrogen to the intermetallic.
22 citations
TL;DR: In this article, the interaction of hydrogen with the surface of previously cleaned TiFe samples was investigated by means of Soft X-Ray Appearance Potential Spectroscopy (SX-APS) and Auger Electron Spectrograph (AES).
19 citations
TL;DR: In this article, the authors used electron and photon-stimulated desorption to directly or indirectly provide atomic and structural information on the chemical state of surfaces and adsorbates on surfaces.
Abstract: Electron- and Photon-Stimulated Desorption can directly or indirectly provide atomic and structural information on the chemical state of surfaces and adsorbates on surfaces. Information is contained in the variation of desorption yield with chemical state, ion energy distributions, ion angular distributions, and in desorption thresholds and spectral dependence. Current models for desorption discuss both ionic and covalent systems and provide considerable insight into the environment of desorbing species. Widely studied examples include oxygen on metals, CO on metals, hydrogen on metals and semiconductors, and cryogenic molecular solids as models for desorption. All of these systems show variations in ion yield with chemical state of the desorbing species which in many cases fit existing models and in many cases suggest new mechanisms of desorption. Ion energy and angular distributions provide signatures of the type of state yielding desorption and the local structure of the desorption site. Desorption spectra can provide electronic and structural details of the bonding site from the analysis of near edge and extended fine structure. Near edge structure can also be used as a signature by comparison to systems of known chemical environment. The above examples of the combined use of the different variations of the desorption experiment are discussed.
16 citations
14 citations
TL;DR: The identical chemical state of three gold atoms in trimeric gold(I) azolates and the Au(I)-Au(III) mixed-valence state in their iodine adducts, Au3(az)3I2, were confirmed by means of 197Au-Mossbauer spectroscopy.
Abstract: The identical chemical state of three gold atoms in trimeric gold(I) azolates and the Au(I)–Au(III) mixed-valence state in their iodine adducts, Au3(az)3I2, were confirmed by means of 197Au-Mossbauer spectroscopy.
12 citations
TL;DR: In this paper, the authors used X-ray photo-electron spectroscopy (XPS) to determine the chemical state of P at grain boundaries, XPS had to be measured for a long time to accumulate the signal from P. The prolonged measurement was possible without contamination by the residual gas because of the high vacuum.
Abstract: Knowledge on the chemical state of phosphorus (P) segregated at grain boundaries in iron is important in discussing the mechanism of grain boundary decohesion by P. In order to determine the chemical state of P at grain boundaries, X-ray photo-electron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used.Fe-P alloy specimens with the P concentration between 0.05mass% and 15.6mass% was fractured in the analyzer chamber of which vacuum was better than 5×10-9Pa(4×10-11torr). Since the amount of P segregated at grain boundaries is small, XPS had to be measured for a long time to accumulate the signal from P. The prolonged measurement was possible without contamination by the residual gas because of the high vacuum. XPS of the segregated P was found to be identical to XPS of P in Fe3P. This result supports the Losch model for the grain boundary decohesion by P, in which a segregated P atom forms a strong bond with surrounding Fe atoms and reduces the strength of bond between Fe atoms neighboring to the P atom.The shape of Auger electron spectrum of P in solid solution varies with the P concentration, but that of the segregated P is independent of the P concentration and identical to that of P in Fe3P. The importance of the variation of the shape of Auger electron spectrum with the P concentration in the quantitative analysis of the segregated P is discussed.
12 citations
IBM1
TL;DR: In this paper, the authors make a brief comparison of analytical techniques yielding information on the composition and chemical states of surfaces and thin films, and the major accent of this treatment is on the fundamental physical processes of each technique as these affect both the sensitivity and our quantitative understanding.
10 citations
TL;DR: In this paper, it was shown that all major species of the solid matrix as well as some important waste species can be detected reliably with X-ray photoelectron spectroscopy (XPS) and Auger electron spectrography (AES) and that the inferred abundances are in good agreement with the nominal stoichiometry.
10 citations
TL;DR: In this article, a state analysis of steel surfaces covered with iron oxides and fluorides was performed using the 9th-order FeKα1 line, which was effective for the analysis of iron compounds especially when the compounds were thicker than the detection depth.
Abstract: Chemical states of steel surfaces covered with iron oxides and fluorides were analyzed by a state analysis method utilizing the 9th-order FeKα1 line. The method was effective for the state analysis of iron compounds especially when the compounds were thicker than the detection depth of the FeKα1 line.
TL;DR: In this article, a mass spectrometer attached with a molybdenum Knudsen cell was used to measure the partial vapor pressures and chemical activities of principal components of SUS 304L austenitic steel.
Abstract: The vaporization of SUS 304L stainless steel was studied by using a mass spectrometer attached with a molybdenum Knudsen cell. The partial vapor pressures and chemical activities of principal components of SUS 304L austenitic steel were determined in the temperature range of 1,300–1,430 K (for Fe and Cr each) and 1,070–1,230 K (for Mn). Activity coefficients, partial free energies of mixing and excess partial free energies of the components Mn, Fe and Cr were computed from the measured partial pressures and chemical activities. The thermodynamic functions obtained are discussed especially in regard of the chemical state of Cr at the surface of SUS 304L stainless steel.
TL;DR: In this article, the results of a combined Auger electron spectroscopic (AES) and X-ray photoelectron spectroscopy (XPS) study of the intergranular embrittlement of polycrystalline Ni by S are described.
TL;DR: XPS studies indicate that the binding energies of the Zr3d electron increase with increasing oxygen deficiency in the surface layer and decrease with its decrease as mentioned in this paper, and ZrO2−x is probably metallic zironium.
Abstract: XPS studies indicate that on the surfaces of untreated ZrCr2 and ZrCr2H3.6 zirconium is detected as ZrO2, ZrO2−x and, probably, metallic zironium. Binding energies of the Zr3d electron increase with increasing oxygen deficiency in the surface layer and decrease with its decrease.
TL;DR: In this article, the chemisorption of carbon monoxide from a 0.5 M aqueous KHCO3 solution on a prereduced Pt/TiO2 surface is shown to be completely inhibited as a consequence of a particular chemical state (negative effective charge) of the platinum atoms.
Abstract: The chemisorption of carbon monoxide from a 0.5 M aqueous KHCO3 solution on a prereduced Pt/TiO2 surface is shown to be completely inhibited as a consequence of a particular chemical state (negative effective charge) of the platinum atoms.
TL;DR: In this paper, XPS studies were conducted on the ZrCr2.6 surface of a ZRCr2H3.6 and showed that it contains Cr2O3, Cr(O), Zr2O and nonstoichiometric ZrO2−x.
Abstract: According to XPS studies, the ZrCr2 and ZrCr2H3.6 surface have been established to contain Cr2O3, Cr(O), Zr2O and nonstoichiometric ZrO2−x. The Cr(O) content increases after thermal vacuum treatment of the samples, particularly after Ar+ sputtering. Active hydrogen evolving from the hydride lattice also promotes the increase in the Cr(O) content. After oxidation, chromium is detected only as Cr2O3.
TL;DR: In this paper, the authors describe new preparations and characterizations of Fe/MgO catalysts using the incipient wetness method, magnesium oxide or hydroxycarbonate are impregnated with aqueous ammonium ferrocyanide.
Abstract: Publisher Summary In catalysis, the production of highly dispersed catalysts is often desirable but one of the major problems is the achievement and maintaining of small particles For metallic catalysts, it is realized by dispersing the metal on a porous carrier In order to stabilize metallic particles, the metal-support interaction should be optimum, ie neither so strong that the reduction to the metallic state is too difficult, nor so weak that high particle mobility results in rapid sintering The chapter describes new preparations and characterizations of Fe/MgO catalysts Using the incipient wetness method, magnesium oxide or hydroxycarbonate are impregnated with aqueous ammonium ferrocyanide The ferrocyanide complex is chosen because of its high stability at basic pH values Impregnation of MgO by iron(III) nitrate is also carried out, and is motivated by our wish to eliminate the influence of the decomposition of the MgO precursor The reduction of the catalysts is followed by thermal analysis (TG-DTA) under hydrogen atmosphere Mossbauer spectroscopy is used to provide information on the chemical state and the degree of reduction of iron in the reduced catalysts Particle sizes are estimated by transmission electron microscopy and by chemisorptions of CO
TL;DR: In this article, the authors used spatially resolved Rutherford backscattering to measure the migration of platinum and vanadium from intermetallic catalysts and to determine their suitability for use under the extreme operating conditions found in phosphoric acid fuel cells.
Abstract: A nuclear microprobe cannot give direct information on the chemical state of an element, but the spatial distribution of elements in a specimen is often determined by the chemical history of the sample. Fuel cells and minerals are examples of complex systems whose elemental distributions are determined by past chemical history. The distribution of catalyst in used fuel cell electrodes provides direct information on the chemical stability of dispersed catalysts under operating conditions. We have used spatially resolved Rutherford backscattering to measure the migration of platinum and vanadium from intermetallic catalysts and to determine their suitability for use under the extreme operating conditions found in phosphoric acid fuel cells. Geologic materials are complex, heterogeneous samples with small mineral grains. The trace element distribution within the individual mineral grains and between different mineral phases is sensitive to the details of the mineral formation and history. The spatial resolution and sub-100-ppm sensitivity available with a nuclear microprobe open up several new classes of experiments to the geochemist. Geochemistry and electrochemistry are two areas proving particularly fruitful for application of the nuclear microprobe.
01 Jan 1983
TL;DR: The process of exciting the electronic structure of stable elements by means of X- or gamma-rays to emit characteristic radiation is termed X-ray energy spectroscopy (XES), fluorescent excitation analysis (FEA), or Xray fluorescence (XRF).
Abstract: The process of exciting the electronic structure of stable elements by means of X- or gamma-rays to emit characteristic radiation is termed X-ray energy spectroscopy (XES), fluorescent excitation analysis (FEA), or X-ray fluorescence (XRF). When an element is exposed to X- or gamma-rays, the energy of which is higher than the binding energy of the K-shell (or L-shell) electrons in that element, vacancies can be created in that shell. That vacancy can be subsequently filled by an L-shell (or M-shell) electron. In this process, the atom can emit a photon with energy K (or L). The energy of this characteristic fluorescent radiation is unique to each element. It depends on the atomic number of the element and ranges from 1 to 100 keV (1 keV = 1,6.10−16 Joule). As the fluorescent excitation involves the K- or L-shells, XRF is not dependent on the chemical state of the element, and the number of characteristic photons emitted by a sample is proportional to the abundance of the element in the sample that is assayed (1,2,3).