Structure of the SiC(0001)-3 × 3-R30° surface after initial oxidation

The structure of the 3 × 3-R30° reconstruction on the (0001) surface of silicon carbide before and after initial oxidation at room temperature was determined with reflection high-energy electron diffraction (RHEED) rocking curves in the one-beam condition and density-functional theory calculations. The structural parameters of the clean surface are in good agreement with previous reports. For the oxidized surface, good agreement between experimental and calculated RHEED rocking curves was obtained for a model with oxygen atoms in the backbonds of the Si adatom and on its top (ad-ins × 3). The atomic positions of the oxidized surface determined from the density-functional theory calculations agree reasonably well with the RHEED results.