Monoisotopic varieties of silicon and germanium with a high chemical and isotopic purity

Abstract

We presented the results on the preparation of high-purity monoisotopic varieties of silicon and germanium. The process involves the separation of isotopes in the form of SiF4 and GeH4 by centrifugation, ultrapurification of volatile compounds, and preparation of poly and single crystals. The attained degree of isotopic and chemical purities of single crystals obtained was shown. The content of the main isotope in the single crystals of 28Si is >99.99% and those in the single crystals of 29Si and 30Si are >99.9%. The specific resistivity of the 28Si single crystals is ∼1 kOhm cm and those of 29Si and 30Si are about 100–150 Ohm cm. The samples of the 76Ge single crystals have the main isotope content of >88 at.% and the difference concentration of electrochemically active impurities of 5·1010 cm−3. The main isotope content in the 74Ge polycrystal is 99.93 at.%. The optical and thermophysical properties of the isotope-enriched silicon and germanium single crystals were measured, which suggest a significant effect of the isopotic composition on thermal capacity, thermal conductivity, luminiscence, and light absorption.