Atomic and electronic structures of [formula omitted] surfaces

Abstract

The atomic and electronic structures of 6H-SiC ( 0 0 0 1 ¯ ) - 3 × 3 reconstructions were analyzed by high-resolution medium energy ion scattering (MEIS) combined with photoelectron spectroscopy. We prepared three types of (3 × 3) surfaces by (a) annealing the Si-rich (2 × 2) surface at 1030 °C, (b) annealing the 3 × 3 silicate surface at 1050 °C, and (c) annealing the RCA-treated surface at 1050 °C in ultra-high vacuum. The present MEIS analysis reveals the fact that the (3 × 3) surfaces consist of a Si-adlayer (1.1 ML), C-adlayer (0.5 ML) and C-adatoms (1/3 ML)/C-adlayer (2/3 ML) on the 1st C–Si bilayer for samples (a), (b) and (c), respectively. Observation of the valence band spectra shows that all the surfaces are semiconducting and have dangling bond states in the band gap (1.4 eV below the Fermi level for sample (a)). The Si-rich surface (a) has one surface-related component in Si 2p and in contrast, the C-rich surfaces (b and c) have two surface-related components in C 1s spectra. It is shown that the (3 × 3) reconstructions of the SiC ( 0 0 0 1 ¯ ) are categorized into the above three types and take different atomic configurations. For the Si-rich (3 × 3) surface, the present analysis supports the structure model proposed by Hoster et al. [H.E. Hoster, M.A. Klakov, B. Bullemer, Surf. Sci. 382 (1997) L658]. The probable structures of the C-rich (3 × 3) surfaces are also discussed in detail.