Interaction of cobalt atoms with an oxidized Si(100)2 × 1 surface

The initial stages of oxidation of a Si(100)2 × 1 surface and the interaction of cobalt atoms with it were studied by core-level photoelectron spectroscopy. The study was carried out with cobalt coverages of up to 8 ML. Computer modeling of the spectra of photoexcited electrons revealed Co atom penetration under the silicon oxide layer, an effect observed even at room temperature. This process was shown to give rise to the disappearance of silicon interface phases at the oxide-layer-silicon boundary and to the formation of a more complex phase involving atoms of Co, O, and Si. After completion of the process, a Co-Si solid solution forms at the interface.     

Electronic spectra of 5,6-polymethylenethiapyrylium salts and certain oxygen analogs

Electronic absorption and emission spectra of substituted 5,6-tri- and 5,6-tetramethylenethiapyrylium salts are examined to determine the influence of the degree and character of substitution of the heterocycle, the size of the condensed alicycle, the nature of the heteroatom and the counterion, and the polarity of the solvent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 198–202, February, 1985.     

Quantum-chemical study of the hydride lability of hydrogen in thiapyrans and related compounds

A method is proposed for the quantitative evaluation of the relative hydride lability of hydrogen in a number of compounds from the hydride ion affinity of the corresponding cations. The relative labilities of H^– in 4H- and 2H-thiapyrans, 4H- and 2H-pyrans, 2H-thiapyran 1,1-dioxide, cyclopentadiene, and cycloheptatriene were determined by the CNDO/2 (complete neglect of differential overlap) method. It is shown that the thiapyran and pyran heterorings are distinguished by high hydride lability of hydrogen; this is evidently the principal reason for their ability to undergo disproportionation. It was established that cycloheptatriene should be a more active hydride-ion donor in nonpolar media. Correlation of the acidities of the examined compounds with the proton affinity of the corresponding anions, calculated by the CNDO/2 method, was noted.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1206–1208, September, 1977     

ESR spectroscopy of copper(ii) complexes with aza- and thia-containing crown ethers

Six copper(ii) chloride complexes with crown ethers containing besides oxygen also nitrogen or sulfur atoms in 15- or 18-membered cycle were studied by ESR and electron absorption spectroscopies. Theg and HFI tensor components determined by spectral simulation indicate rhombic symmetry and localization of an unpaired electron on the d _xy orbital for all the complexes. The unpaired electron fractions on - and -type metal ion and ligand AO were estimated from ESR and absorption spectra using LCAO MO method. Both - and -type bond covalences were shown to be greater in these complexes compared to only oxygen-containing crown ether complexes. The temperature dependence of g and A components in some complexes may be due to conformational changes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1938–1944, November, 1994.The present work was carried out with financial support from the Russian Foundation for Basic Research (Project 93-03 04089).     

Moment Analysis in Non-Linear Frontal-Elution and Elution Chromatography

Analytical formulae are presented for the statistical moments of an output chromatographic curve for non-linear distribution isotherms at a very narrow feed band (“elution chromatography”). Non-linear “frontal-elution chromatography”, i.e., the case of a very wide feed band, is also considered. The analytical expressions characterize the position and the width of sorption and desorption boundaries of the output curve. The column length at which a constant configuration of the sorption (or desorption) boundary is attained is dependent in the curvature of the isotherm and on the plate height. The results have been confirmed experimentally.     

Atomic structure of silver clusters on silicon

The atomic structure of silver clusters formed on a Si(111)-7×7 single crystal surface by annealing a silver thin film condensed at room temperature is investigated by the diffraction of medium-energy quasielastically scattered electrons. Simulation of the diffraction pattern obtained within a nearly complete electron reflection hemisphere shows that the silver islands formed on the silicon have an ordered structure and a fixed orientation relative to the substrate. Close-packed Ag(111) monolayers, which form a face-centered cubic structure, are arranged parallel to the surface, the direction of these microcrystals being antiparallel to the axis of the substrate. Zh. Tekh. Fiz. 67, 62–66 (December 1997)     

Interaction of cobalt atoms with an oxidized Si(111)7 × 7 surface

Technical Physics - The interaction of cobalt atoms with a Si(111)7 × 7 surface subjected to in situ oxidation in an oxygen atmosphere at a pressure of 10?5 Pa, an exposure of 20 L, and...     

Influence of Orientation of a Silicon Substrate with a Buffer Silicon Carbide Layer on Dielectric and Polar Properties of Aluminum Nitride Films

Physics of the Solid State - Dielectric and polar properties of aluminum nitride (AlN) thin films epitaxially grown on differently oriented silicon substrates with the p-type conduction and a...     

Modification of the electronic structure of graphene by intercalation of iron and silicon atoms

The ab initio calculations of the electronic structure of low-dimensional graphene–iron–nickel and graphene–silicon–iron systems were carried out using the density functional theory. For the graphene–Fe–Ni(111) system, band structures for different spin projections and total densities of valence electrons are determined. The energy position of the Dirac cone caused by the p _z states of graphene depends weakly on the number of iron layers intercalated into the interlayer gap between nickel and graphene. For the graphene–Si–Fe(111) system, the most advantageous positions of silicon atoms on iron are determined. The intercalation of silicon under graphene leads to a sharp decrease in the interaction of carbon atoms with the substrate and largely restores the electronic properties of free graphene.