Stacking rearrangement at 6H–SiC(0 0 0 1) surfaces during thermal hydrogenation

We have investigated the Si–H stretch mode on 6H–SiC(0 0 0 1) and 3C–SiC(1 1 1) after thermal hydrogenation by Fourier-transform infrared absorption spectroscopy. On 6H–SiC(0 0 0 1) two Si–H stretch modes at (2128.0±0.6) cm−1 and (2133.5±0.6) cm−1 are observed. The intensity ratio of the two absorption lines varies with preparation temperature. On 3C–SiC(1 1 1) essentially a sole mode is observed at (2128.4±1.0) cm−1 at all temperatures. The two modes observed on 6H–SiC(0 0 0 1) are explained in terms of cubic and hexagonal stacking arrangements below the surface. The variation of the intensity ratio of the two modes on 6H–SiC(0 0 0 1) indicates a temperature dependent preference for cubic or hexagonal termination. Possible mechanisms for the stacking rearrangement are discussed.