Structure of hydrogenated amorphous silicon-carbon alloys as investigated by extended x-ray-absorption fine structure

Abstract

We have studied the local structure of hydrogenated amorphous silicon-carbon alloy films, a-${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{C}}_{\mathit{x}}$:H, by measuring the extended x-ray-absorption fine structure at the Si K edge. We find that first-coordination-shell average bond lengths are 2.35 Å for Si-Si and 1.86 Å for Si-C and are constant with concentration to within ±0.015 Å. By comparing the composition of the first coordination shell around Si with the average concentration, we show that the alloy tends to be chemically ordered, in that heteroatomic bonds are preferred.