In situ surface phases and silicon-adatom geometry of the (2 x 2)C structure on 6H-SiC(000(1)over-bar)

A (2 x 2) reconstruction on 6H-SiC(000 (1) over bar), obtained by annealing an ex situ prepared or a silicon-capped sample, was investigated using quantitative low-energy electron diffraction. The surface geometry is characterized by one silicon adatom per unit cell in three-fold hollow coordination (H-3 sites). The topmost two substrate bilayers are found to be preferentially rotated by 60 degrees with respect to each other, corresponding to a hexagonal type of stacking present at the very surface. (C) 2000 Elsevier Science B.V. All rights reserved.