Variable structural order in amorphous silicon

Raman scattering and optical-absorption spectra in low-pressure, rf-sputtered $a$-Si are shown to exhibit a continuous variation with deposition temperature. A direct correspondence between changes in the inverse width of the TO-like phonon band and the optical gap is observed in sputtered and chemical-vapor-deposited $a$-Si. The results are interpreted in terms of intrinsic changes in network short-range order of $a$-Si with temperature which yield substantial modifications of the vibrational and electronic states.