Formation of a SiC buffer layer by reaction of Si (100) with methane and hydrogen plasma

The reaction of Si (100) surfaces at T = 950 degrees C with radicals of met hane obtained in a low-power-density glow discharge plasma, has been studie d by combining in situ surface science techniques (x-ray photoemission spec troscopy and high electron energy diffraction) and ex situ analytical techn iques (atomic force microscopy and infrared absorption). An analysis of C 1 s and Si 2p core-level shifts combined with the examination of the valence- band curves showed that the obtained buffer layers were stoichiometric. For long carbonization times (>30 min) the formation of a carbon rich surface was observed. To understand the mechanism of hetero-epitaxial silicon carbi de (SiC) buffer layer growth, the early stage of SiC nucleation was observe d by atomic force microscopy and reflection high-energy electron diffractio n. The results suggest that three-dimensional epitaxial islands nucleate at the earliest growth stage followed by a further Volmer-Weber growth until the formation of a carbon rich surface. The growth mechanism of the SiC buf fer layer is discussed on the basis of a reported model.