Reconstruction of the 6H–SiC(0001) √3×√3-R30° surfaces by adsorption of hydrogen in ultra high vacuum

Reconstruction of the 6H–SiC(0001)√3×√3-R30° surfaces in ultra high vacuum (UHV) has been studied by rocking curves of reflection high energy electron diffraction (RHEED) intensities and Auger electron spectroscopy (AES). It is found that the silicon rich √3×√3 surface is unstable in UHV. This √3×√3 surface transforms into the carbon rich 1×1 surface in rather short time. The phase transition is concluded to be caused by atomic hydrogen adsorbed on the silicon rich surface. Annealing the 1×1 surface leads to the carbon rich √3×√3 surface, which transforms into the silicon rich √3×√3 surface by successive annealing in UHV. The results show that silicon adatoms on the silicon rich √3×√3 surface is not etched by the adsoption of hydrogen but reside on the surface as silicon clusters in the reconstruction process to work as a silicon source in the successive annealing.