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This review is devoted to the consideration of prospects and directions for the development of methods and approaches to the analysis of high-purity industrial gases and volatile hydrides, chlorides, fluorides, and organoelement compounds with natural and isotopically enriched compositions. The currently known capabilities for the determination of impurities in them using mass spectrometry, IR spectroscopy, gas chromatography, and chromatography–mass spectrometry are analyzed. [ABSTRACT FROM AUTHOR]

High-purity isotopically enriched germanium has been prepared by a hydride method, and the main factors capable of reducing the germanium yield in the monogermane pyrolysis process have been identified. To raise the germanium yield, we have optimized pyrolysis conditions in a laboratory-scale flow apparatus. At a monogermane flow rate at the reactor inlet of 30 mL/min, the optimal monogermane decomposition temperature is 420–450°C. Such conditions ensure a decomposition rate of ~6 g/h and a high product yield and make it possible to obtain most of the germanium in polycrystalline form. Using isotopically enriched monogermane pyrolysis, we have obtained high-purity isotopically enriched germanium samples in the form of polycrystalline ingots with a yield above 95%. The ingots are n-type and range in resistivity from 25 to 50 Ω cm. The content of regulated impurities in the 72Ge-,73Ge-, 74Ge-, and 76Ge-enriched germanium ingots thus prepared does not exceed 0.01 to 1 ppm by weight. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It is reported on production of germanium stable isotopes 72Ge, 73Ge,74Ge,76Ge single crystals with high isotopic and chemical purity by hydride method. Separation of isotopes was carried out by centrifugal method using monogermane as the initial volatile substance. Samples of monoisotopic monogermanes 72GeH4, 73GeH4,74GeH4, 76GeH4 were purified by the method of low-temperature rectification. Elementary polycrystalline germanium was extracted by pyrolysis from respective monogermane and purified from impurities by the method of zone melting. Single crystals of germanium isotopes were grown by Czochralski method. The content of the main isotope in the produced single crystals 72Ge, 73Ge,74Ge,76Ge was 99.98; 99.90; 99.93 and 87.5 at. %, respectively, and the content of the impurities of stable elements was less than 10−5 -10−6 mass %. [ABSTRACT FROM AUTHOR]