ANNEALING TEMPERATURE-DEPENDENCE OF THE OPTICAL-PROPERTIES OF SPUTTERED HYDROGENATED AMORPHOUS-SILICON CARBIDE

Optical measurements (UV-visible-NIR) have been performed at room temperature on sputtered a-SiC:H samples after annealing at temperatures, T(a), between 673 and 973 K. The complex dielectric constant in the range of 0.8-6.5 eV and, using the Wemple-Di Domenico model, the dispersion energy, the Penn gap, the valence electron density, the plasmon energy and the Fermi energy were deduced. The energy gap was determined by means of various models. The decrease of energy gap and the increase of the valence electron density on one hand, and the shift of the exponential absorption edge on the other hand, indicate the coupling of the valence and the conduction band states by optical photon as the annealing temperature increases. Moreover, as T(a) exceeds 773 K, the polycrystalline phase can be observed to germinate inside the pre-existing amorphous phase.