Carbonization of Si(111)-$7\times 7$ Surface Using CH4 with Hot Tungsten Filament

概要

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The reaction of CH4 on a Si(111)-$7\times 7$ surface is investigated by reflection high-energy electron diffraction (RHEED) analysis, quadrupole mass spectroscopy (QMS) and scanning electron microscopy/energy dispersive analysis of X-ray (SEM/EDAX). The RHEED patterns during CH4 exposure indicate the evolution of structures such as $\delta$-$7\times 7$, $1\times 1$, $\sqrt{3}\times\sqrt{3}$ and SiC for various exposures at temperatures from room temperature (RT) up to approximately 800 °C. A mass spectrum shows that CH4 decomposition products are primarily CH3, CH4, and H2 at a tungsten filament temperature of 1500 °C. A SEM image of the SiC formed at 825 °C and 7920 L shows that the surface is rugged and consisted of hills and valleys. On the basis of the EDAX measurements, it is determined that the SiC layers are C-rich at the hill and Si-rich at the valley. It is found that the SiC layer is generated only after the formation of the $\sqrt{3}\times\sqrt{3}$ structure.
2006-08-15