MORPHOLOGY, BOND SATURATION AND RECONSTRUCTION OF HEXAGONAL SIC SURFACES

The atomic structure of silicon carbide (SiC) surfaces in hexagonal or ientation is investigated with the main emphasis put on Surface morpho logy and dangling-bond saturation either by adspecies or by surface re construction. By using quantitative low-energy electron diffraction (L EED) intensity analysis, the atomic geometry immediately after ex situ chemical treatment is determined for 4H and 6H samples in both hexago nal orientations and a 3C-SiC(111) surface. The step structure is foun d to be directly related to the polytype of the samples from morpholog y studies by using scanning-tunneling microscopy (STM). This is in agr eement with the surface layer stacking sequence determined in the LEED analysis. Dangling bonds of the topmost surface atoms are fully satur ated by adspecies that remain from the chemical preparation. Reconstru ction phases prepared under ultra-high vacuum conditions are investiga ted using the in situ combination of LEED and STM. Here the number of dangling bonds is reduced by a reconstruction pattern that involves ad atoms or adclusters for the more silicon rich-phases and by a commensu rate overlayer of large periodicity in the more carbon-rich structures .