Frequency Tuning of Terahertz Stimulated Emission under the Intracenter Optical Excitation of Uniaxially Stressed Si:Bi

Semiconductors - The results of experimental and theoretical investigations of terahertz-emission-spectrum tuning by means of uniaxial stress of a silicon crystal doped with shallow bismuth donors...     

Terahertz emission at impurity electrical breakdown in Si(Li)

Terahertz electroluminescence caused by impurity-induced breakdown in lithium-doped silicon crystals is studied. The spectrum of the terahertz emission exhibits lines corresponding to intracenter electronic transitions between excited states of the impurity and sublevels of the ground state of the lithium donor. The spectrum also shows a background signal, which, apparently, is a manifestation of the effects due to heating at electric excitation.     

Development and experimental study of the neutron beam at the synchrocyclotron of the Petersburg Nuclear Physics Institute for radiation tests of electronic components

A neutron beam with an energy spectrum resembling that of atmospheric neutron radiation has been developed at the 1000-MeV synchrocyclotron of the Petersburg Nuclear Physics Institute. The beam is intended for testing the radiation resistance of electronics and meets the requirements of the JEDEC international standard. The only test facility in which the neutron spectrum is close to the standard in the energy range of 0.1–750 MeV has been developed at the Los Alamos National Laboratory on the basis the LAMPF linear proton accelerator and used by aviation and space companies of the United States, Europe, and Asia to test their electronic equipment. In contrast to the test facilities in Los Alamos and Uppsala (Sweden), the method of neutron production on an internal accelerator target is used by the Petersburg Nuclear Physics Institute. The development of the neutron beam and the test facility extends considerably the experimental potential of radiation research and can act as a basis for establishing a unique center for radiation tests of aviation and space electronic equipment in compliance with the requirements of international standards.     

Sources of Carbon Impurities in the Preparation of High-Purity Monoisotopic <Superscript>28</Superscript>Si by a Hydride Method

This paper examines sources of carbon impurities in polycrystalline monoisotopic ²⁸Si prepared by a hydride method. Analytical data on the concentrations of carbon-containing impurities in volatile silicon compounds (²⁸SiH₄ and ²⁸SiH₄), process gases (Ar and H₂), and polycrystalline ²⁸Si are used to identify the major sources of carbon in the polycrystalline ²⁸Si prepared by the hydride method. These are the starting ²⁸SiH₄ and calcium hydride used in ²⁸SiH₄ conversion into ²⁸SiH₄. The rate of carbon intake into polycrystalline silicon from the apparatus material during the monosilane pyrolysis process does not exceed 9 × 10¹¹ cm^–2 h^–1. Polycrystalline silicon has been precipitated from monosilane with different concentrations of hydrocarbon impurities. At hydrocarbon concentrations in the range 10^–4 to 10^–3 mol %, the carbon concentration in the monosilane correlates with that in the silicon obtained from it. High-purity monosilane has been used to prepare polycrystalline ²⁸Si samples with concentrations of carbon impurities in the range (0.8–2.3) × 10¹⁵ cm^–3. Based on calculations of the carbon impurity distribution along the length of a zone-refined ingot, we examine the effect of the initial carbon concentration in the starting polycrystal on the yield of single-crystal monoisotopic ²⁸Si. Requirements are formulated for the carbon concentration in polycrystalline ²⁸Si which ensure a high yield of single crystals with parameters suitable for metrological applications.     

Estimation of solubility and thermodynamic characteristics of solvation of radon in deuterated water at 0.1 MPa and 278–318 K

The concentration of Rn in saturated solution in D₂O at 101 325 Pa and 278.15–318.15 K (at 5 K interval) was estimated by the Karapet’yants method of comparative calculation from original and published data on the solubility of noble gases He-Xe in H/D water isotopomers and of Rn in H₂O. Thermodynamic functions of Rn solvation (Δ_sol G ⁰, Δ_sol H ^∞, Δ_sol S ⁰, and Δ_sol C _p ^∞ ) in H₂O and D₂O and the corresponding H/D isotope effects were calculated by the original method. The characteristics obtained for the D₂O-Rn system are consistent with the previously found trends in variation of thermodynamic isotope effects of solvation of noble gases (He-Xe) in aqueous solution with increasing temperature.     

Synthesis of CN<Subscript>x</Subscript> nanotubes using catalysts prepared from zinc and nickel bimaleates

Nitrogen-containing carbon nanotubes have been prepared via acetonitrile (CH₃CN) pyrolysis at 850°C catalyzed by nanoparticles produced by the thermal decomposition of zinc and nickel bimaleates and their solid solutions. The synthesized samples have been characterized by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. The results demonstrate that increasing the zinc content of catalyst nanoparticles reduces the yield of carbon nanotubes and increases the nitrogen content of the material. The high synthesis temperature gives rise to zinc vaporization, which influences the growth process, increasing the nanotube diameter, reducing the wall thickness, and lowering the structural perfection of the graphite layers.     

The treatment of biological material by Falck's method and its modifications using a device of original design

Automation of the process of detecting adrenergic nerve structures helped obtain reliable positive results even in cases with low mediator concentration in body tissues. We have elaborated a new method of subsequent staining and microphotographing of biological specimens which permit registration of specific features of adrenergic nerve terminals histologic architecture and their cellular microenvironment.     

Standard impedance simulator

The principles of a method of isoperimetric high-frequency induction logging (IHIL) are described. Substantiation is provided for a procedure which uses an annular impedance simulator to check the metrological characteristics of IHIL equipment. The design of the simulator and the sequence of operations performed in using it are described, in addition to a method for testing the simulator. Values are given for the errors of the simulator's parameters. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 57–59, October, 1998.