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

Reconstruction of the 6H-SiC(0001)root3 x root3-R30degrees 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 root3 x root3 surface is unstable in UHV. This root3 x root3 surface transforms into the carbon rich 1 x 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 x 1 surface leads to the carbon rich root3 x root3 surface, which transforms into the silicon rich root3 x root3 surface by successive annealing in UHV. The results show that silicon adatoms on the silicon rich root3 x root3 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. (C) 2002 Elsevier Science B.V. All rights reserved.