New allotropic form of silicon

A new allotropic form of amorphous silicon with sp hybridization of the valence electrons is discovered. The new material consists of linear chains of atoms. A small fraction of the atoms are in the sp ² state. Acting as bridges, these atoms couple the linear chains into a single random network. This conclusion is based on an analysis of experimental data on the effect of annealing and ion implantation on the structure of the short-range order and the properties of amorphous-silicon films obtained by different methods. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 646–649 (10 May 1998)     

A promising polymer composite material for increasing the efficiency of recovery of basic parts of automotive engineering

It is theoretically proven that filling of elastomers with disperse metal powders allows decreasing the compliance of supports, increasing heat removal from a bearing assembly, decreasing the temperature and solidification time, and increasing the tolerance thickness of a polymeric enclosure during recovery of fitment bores in basic parts. The results of an experiment in the form of a regressive model and optimal content of polymer composite material based on the F-40 elastomer are presented.     

X-ray fluorescence determination of the surface density of thin chromium and iron films using reference samples of elements with close atomic numbers

In X-ray fluorescence determinations of the surface density of thin chromium and iron films, we studied the possibility of using an approach based on the application of reference samples of elements with close atomic numbers. It was shown that the proposed diagnostic approach ensures the determination of the surface density of films with rather high precision.     

Matrix Effect in the Determination of Impurity Elements in Iron and Its Compounds by Atomic Emission Spectrometry

Changes in analytical line intensities of some trace impurities of p and d elements in the iron oxide–graphite powder system were studied at different concentrations of iron in the system. The unfavorable effect of changes in the iron concentration on the results of analysis was revealed, and recommendations for its elimination are given.     

Synchrotron investigations of the specific features in the electron energy spectrum of silicon nanostructures

The Si L _{2, 3} x-ray absorption near-edge structure (XANES) spectra of porous silicon nanomaterials and nanostructures with epitaxial silicon layers doped by erbium or containing germanium quantum dots are measured using synchrotron radiation for the first time. A model of photoluminescence in porous silicon is proposed on the basis of the results obtained. According to this model, the photoluminescence is caused by interband transitions between the energy levels of the crystalline phase and oxide phases covering silicon nanocrystals. The stresses generated in surface silicon nanolayers by Ge quantum dots or clusters with incorporated Er atoms are responsible for the fine structure of the spectra in the energy range of the conduction band edge and can stimulate luminescence in these nanostructures.     

PECVD synthesis of As–S glasses

Chalcogenide glasses of the As–S system were first obtained by melting of solid products of interaction between As and S in low-temperature argon plasma. The plasma-chemical synthesis was performed at a reactor wall temperature not exceeding 250°C. The content of S in the As–S glasses is 54 to 72 mol %. The elemental, phase, and impurity composition of the glasses and their glass-transition point and optical properties were studied.     

Raman spectroscopy of amorphous silicon subjected to laser annealing

The effect of laser radiation power on the Raman spectra of amorphous silicon obtained by electron-beam evaporation has been revealed. The formation of nanocrystalline inclusions in the amorphous matrix under exposure to a laser with a power of more than 2.5 mW is established by Raman spectroscopy and photoluminescence. The influence of the fabrication conditions (substrate temperature and annealing in a vacuum) of source amorphous silicon films on the formation of nanocrystalline inclusions formed by subsequent laser treatment has been investigated. The features of silicon nanocrystal formation in cases when the original amorphous silicon film is obtained at a substrate temperature of ∼250°C have been revealed. These features may be associated with the presence of silicon-silicon multiple bonds.     

Polyconjugated Silicon Polymers

The geometrical and electronic structure of polyconjugated silicon polymers was calculated by ab initio quantum-chemical methods. The polymers are built from linear chains of Si atoms with polyyne and cumulene bond systems. The results of calculations agree with the experimental data on the structure of silicyne — an amorphous substance prepared by annealing hydrogenated amorphous silicon in vacuum. The agreement between the theoretical and experimental data is interpreted as evidence in favor of the existence of polyconjugated silicon polymers in the form of the structural fragments of silicyne. The existence of such polymers points to the ability of elementary silicon to form new allotropic forms analogously to carbon.     

X-ray Fluorescence Analysis of Powdered As x Se100 – x Samples

A procedure was developed for the X-ray fluorescence determination of components in powdered samples of As _x Se_{100 – x} , and its performance characteristics were determined. The relative standard deviation was 0.15% for the major components. The results of X-ray fluorescence analysis were in good agreement with data of atomic absorption spectroscopy.