STRUCTURE OF SiC FILMS GROWN ON Si(111) AND (110) SUBSTRATES BY SOLID-SOURCE MOLECULAR BEAM EPITAXIE. U. Kaiser, A. Fissel, W. Richter, S. B. Newcomb*, W. M. Stobbs*, Institut für Festkörperphysik, Friedrich-Schiller-Universität Max-Wien-Platz 1, D-07745 Jena, *Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ

TEM and AFM studies have been carried out to demonstrate the influence of growth parameters and substrate orientation on the structure of SiC films deposited simultanously and alternately from two sources by solid-source molecular beam epitaxy at low substrate temperatures (750 C-900 C). At 750 C and high growth rates (>2nm/min) polycrystalline columnar films were grown which show a weak orientation relationship to the substrate. While growing the films under conditions for Si stabilization at the surface and over the substrate temperature range of 800 C to 850 C at high rates, the films are strongly textured but still grow with a columnar morphology. Clear evidence for the outdiffusion of Si from the substrate is found, leading to porous regions in the substrate at temperatures up to 800 C and to voids above 800 C. At growth rates below 1nm/- min and a certain adatom ratio the nucleation mode changes from 3 to 2 dimensional and single crystalline epitaxial cubic films were grown. The influence of the adatom ratio Si:C on the growth and on the defect formation is discussed at 3 different Si:C adatom ratios (0.95, 1.05, 1.20). When the layer is deposited under slow and less kinetically controlled conditions using an alternating supply of Si and C controlled to the atomic plane level, single crystalline cubic SiC films with very flat surfaces are formed which tend to establish the hexagonal polytype. Differences in the growth on (111) and (110) substrates might be expected and are discussed as result of the differing crystallographies at the interface.