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 methane obtained in a low-power-density glow discharge plasma, has been studied by combining in situ surface science techniques (x-ray photoemission spectroscopy and high electron energy diffraction) and ex situ analytical techniques (atomic force microscopy and infrared absorption). An analysis of C 1s 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 carbide (SiC) buffer layer growth, the early stage of SiC nucleation was observed by atomic force microscopy and reflection high-energy electron diffraction. 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 buffer layer is discussed on the basis of a reported model.