VARIATIONS OF VIBRATIONAL LOCAL MODES AND ELECTRONIC STATES OF HYDROGENATED AMORPHOUS-SILICON CARBIDE UNDER THERMAL ANNEALING

Both vibrational and electronic properties of some local bonding struc tures of hydrogenated; amorphous silicon carbide are studied. The dens ities of states for the bulk SIC, -CSi3 (carbon atom with dangling bon d), -SiC3, CHn and SiHn groups are calculated. The calculated results are used to explain the variation of the local bonding structures of a -Si1-xCx : H under thermal annealing. In the vibrational study, the th ermal annealing of the film causes the weakening of the CH bond stretc hing and CH3 wagging/rocking modes, the weakening of the SiH bond stre tching mode and the appearance of an Si-C vibrational mode at a lower frequency. In the electronic study, the thermal annealing of the film causes the CH- and SiH-induced states to diminish and the shoulder sta tes on top of the valence band to grow. All these phenomena can be exp lained by the evolution of hydrogen from the surfaces of the microvoid s. The microstructures are changed from CH3 to CH or carbon with dangl ing bond and from SiHn to silicon with dangling bond. Both theoretical vibrational and electronic studies give consistent explanations of th ese phenomena. (C) 1998 Elsevier Science Ltd. All rights reserved.