Atomic structure determination of the Si-rich β-SiC(001)3×2surface by grazing-incidence x-ray diffraction: A stress-driven reconstruction

Abstract

The atomic structure of the Si-rich \ensuremath{\beta}-SiC(001) $3\ifmmode\times\else\texttimes\fi{}2$ surface reconstruction is solved by grazing-incidence x-ray diffraction with surface and subsurface structure determination. The reconstruction involves three Si atomic planes $(\frac{1}{3}+\frac{2}{3}+1$ Si monolayers) in qualitative agreement with ab initio theoretical calculations. The first plane includes Si dimers that are asymmetric with a 0.1 \AA{} height difference between Si atoms while the second plane includes Si dimers having alternating long (2.41 \AA{}) and short (2.26 \AA{}) lengths resulting in long-range influence with no buckling of the top surface dimers, in strong contrast to other group-IV semiconductors. Dimerization is also shown to take place in the third Si plane with a dimer having a bond length at 2.38 \AA{}. In addition, a large Si interlayer spacing is found between the reconstructed planes at 1.56 \AA{}, significantly larger than that for bulk SiC (1.09 \AA{}) and Si (1.35 \AA{}) interlayer distances, indicating a very open surface. The results suggest that stress is at the origin of this complex surface organization.