High Resolution Radial Distribution Function of Pure Amorphous Silicon

Abstract

The structure factor $S(Q)$ of high purity amorphous Si membranes prepared by ion implantation was measured over an extended $Q$ range ( $0.03--55{\AA{}}^{\ensuremath{-}1}$). Calculation of the first neighbor shell coordination ( ${C}_{1}$) as a function of maximum $Q$ indicates that measurement of $S(Q)$ out to at least $40{\AA{}}^{\ensuremath{-}1}$ is required to reliably determine the radial distribution function (RDF). A $2%$ change in ${C}_{1}$ and subtle changes in the rest of the RDF were observed upon annealing, consistent with point defect removal. After annealing at 600 \ifmmode^\circ\else\textdegree\fi{}C, ${C}_{1}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.88$, which would explain why amorphous Si is less dense than crystalline Si.