Atomic structure determination of the Si-rich β-SiC(001) 3x2 surface by grazing-incidence x-ray diffraction:: A stress-driven reconstruction -: art. no. 165321

The atomic structure of the Si-rich beta-SiC(001) 3x2 surface reconstruction is solved by grazing-incidence x-ray diffraction with surface and subsurface structure determination. The reconstruction involves three Si atomic planes (1/3 + 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 Angstrom height difference between Si atoms while the second plane includes Si dimers having alternating long (2.41 Angstrom) and short (2.26 Angstrom) 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 Angstrom. In addition, a large Si interlayer spacing is found between the reconstructed planes at 1.56 Angstrom, significantly larger than that for bulk SiC (1.09 Angstrom) and Si (1.35 Angstrom) interlayer distances, indicating a very open surface. The results suggest that stress is at the origin of this complex surface organization.