Correlation of structure and optical properties of an annealed hydrogenated amorphous silicon-carbon alloy film

Abstract

A hydrogenated amorphous silicon-carbon (a-Si 0.76C 0.24:H) film has been prepared via the glow discharge decomposition of SiH 4 and C 2H 4. The optical constants of this alloy film have been determined as a function of annealing temperature T a for photon energies between 1.5 and 4.75 eV. The refractive index n and its imaginary part k show small but significant variation with annealing temperature. The optical energy gap E opt also exhibits interesting variation with annealing temperature, decreasing with increasing annealing temperature up to T a = 650°C and then increasing above this temperature. Further, E opt is found to be correlated with the inverse of the full width at half-maximum of the SiC and the SiO IR stretch absorption mode, which seems to indicate that the changes in E opt are structural in origin and that phonon order correlates well with electronic order.