Preparation of Pure Silicon by the Hydrogen Reduction of Silicon Tetraiodide

Abstract

The reduction of silicon tetraiodide by hydrogen to form pure silicon and hydrogen iodide has been investigated. The reaction is heterogeneous, taking place on a hot surface. Dense silicon layers as well as crystals can be deposited. The reaction gives a chemical yield as high as 96%, but the over‐all best conditions found resulted in a rate of deposition of 4.4 g Si/dm2/hr at a chemical yield of 55%. Data on the purity of the silicon obtained are presented.The reaction of silicon and iodine to form silicon tetraiodide and the fractional distillation of this compound are discussed. An apparatus is described which permits good control over the composition of a mixture consisting of two gaseous reactants, one of which is generated from the liquid state by vaporization at a uniform rate of flow.