Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

GaAs formation by reduction of As2O3 and Ga2O3 at SiO2/GaAs oxides/GaAs interfaces

Abstract: SiO2/GaAs interfaces have been obtained by deposition of Si on oxidized GaAs(110) surfaces, with the reduction of As and Ga oxides to form Si oxide. High resolution photoemission studies have been performed to elucidate the chemical state of the atoms liberated from the oxide. The reduction of As oxides, faster than that of Ga oxides, produces an As enrichment at the interface, that creates deviations from GaAs stoichiometry. This As excess appears in the high resolution spectra as a component with an energy shift between 0.45 and 0.65 eV from the GaAs substrate signal. Subsequent reduction of Ga oxides produces the decrease of the component related to As excess. In any stage of the process no segregation of Ga appears from the spectra. Finally the As‐excess component vanishes, showing that it reacts with the liberated Ga atoms to form again GaAs. A quantitative analysis of the photoemission intensities has allowed the establishment of a structural model of the atomic arrangement during the chemical changes.

Chemical History with a Nuclear Microprobe

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.

Upgrading Properties of ZnSe Thin Films by Means of Quaternary (Co 2+ , Cd 2+ ) Doping

Abstract: The Zn1-x-yCoxCdySe (0 ≤ x = y ≤ 0.15) thin films were deposited onto the micro-glass substrate via solution growth technique and studied through wet ability, compositional analysis, and morphological observations. The film surface was observed to be hydrophobic in nature. Compositional and elemental analysis confirmed the presence of Zn, Co, Cd and Se elements in Zn1-x-yCoxCdySe thin films, whereas, chemical states as 2+, 2+, 2+ and 2− was observed in XPS. Surface morphology shows a progression of fuzzy multifaceted crystallite network to globule decorated multifaceted network of crystallites.

Polymer-assisted deposition of co-doped zinc oxide thin films for the detection of aromatic organic compounds.

Abstract: Co-doped Zinc oxide thin films are deposited onto SiO2/Si substrate by polymer-assisted deposition method. The surface morphology, structures and chemical states of the thin films are examined by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gas-sensing properties of the thin films upon exposure to aromatic organic compound vapors are also investigated. Co-doping is shown to be very effective in enhancing the response of ZnO thin film to aromatic organic compound.