Raman spectra and structure of amorphous Si

Abstract

In 1985, Beeman, Tsu, and Thorpe established an almost linear relation between the Raman transverse-optic (TO) peak width \ensuremath{\Gamma} and the spread in mean bond angle \ensuremath{\Delta}\ensuremath{\theta} in $a\ensuremath{-}\mathrm{Si}.$ This relation is often used to estimate the latter quantity in experiments. In the last decade, there has been significant progress in the computer generation of sample networks of amorphous silicon. Exploiting this progress, this paper presents a more accurate determination of the relation between \ensuremath{\Gamma} and \ensuremath{\Delta}\ensuremath{\theta} using 1000-atom configurations. Also investigated and quantified are the relations between the TO peak frequency and the ratio of the intensities of the transverse-acoustic (TA) and TO peaks, both as functions of \ensuremath{\Delta}\ensuremath{\theta}. As \ensuremath{\Delta}\ensuremath{\theta} decreases, the TA/TO intensity ratio decreases and the TO peak frequency increases. These relations offer additional ways to obtain structural information on $a\ensuremath{-}\mathrm{Si}$ from Raman measurements.