High Resolution Radial Distribution Function of Pure Amorphous Silicon

The structure factor $S(Q)$ of high purity amorphous Si membranes prepared by ion implantation was measured over an extended Q range ( 0.03--55^-1). Calculation of the first neighbor shell coordination ( C₁) as a function of maximum Q indicates that measurement of $S(Q)$ out to at least 40^-1 is required to reliably determine the radial distribution function (RDF). A $2%$ change in C₁ and subtle changes in the rest of the RDF were observed upon annealing, consistent with point defect removal. After annealing at 600 ^∘{}C, C₁0ex0ex=0ex0ex3.88, which would explain why amorphous Si is less dense than crystalline Si.