Structural order in anneal-stable amorphous silicon

Raman scattering is reported on anneal-stable $a$-Si films prepared by chemical-vapor deposition (CVD). In contrast to earlier work, substantial changes are observed in the phonon spectrum and Raman matrix elements relative to $a$-Si deposited by other techniques. The results indicate improved short-range order associated with a decrease in bond-angle fluctuations in CVD $a$-Si. While the CVD $a$-Si spectra are similar to those of glow discharge $a-{\mathrm{Si}}_{0.92}{\mathrm{H}}_{0.08}$, small differences suggest enhanced order in the H alloy. The results indicate that small changes in short-range order may appreciably modify the properties of $a$-Si.