A quantitative study on the growth of silicon whiskers from silane and germanium whiskers from germane

Abstract

The impurity-induced nucleation and the kinetics of the growth of filamentary crystals of silicon and germanium from silane and germane respectively have been studied in a closed system. Silicon whiskers were grown on heated substrates at temperatures between 550 and 900 °C, germanium whiskers at temperatures between 300 and 500 °C, both at hydride pressures between 5 and 100 Torr, and with Au as impurity. Whisker growth was also obtained with Ag, Cu, Ni and Pd, but not with In, Sn and Bi. The rates of growth of the whiskers in the length direction increase with increasing substrate temperature and hydride pressure, and are of the order of a hundred times higher than the rates of thickness growth of whiskers and substrate. As compared with the non-impurity aided deposition of Si and Ge from the hydrides, where there is an exponential relation between deposition rate and reciprocal temperature, the effect of the growth stimulus at the tip is reflected in a decrease of the activation energy and an increase in the pre-exponential factor. In terms of the VLS mechanism the catalyzed decomposition reaction at the V-L interface is the rate-controlling step.