Photoemission study of Si-rich 4H-SiC surfaces and initial SiO2/SiC interface formation -: art. no. 195335

Photoemission studies of Si-rich polar and nonpolar 4H-SiC surfaces before and after oxygen exposure,, are reported. For the clean Si-rich (0001)-3 X 3 Surface. three prominent surface-shifted components are revealed in the Si 2p spectrurn. This observation agrees well with the structural model suggested for this surface but disagrees with earlier results where only two surface-shifted Si 21) component,, were identified. Also for the other three Si-rich surfaces investigated three similar surface components are revealed although with different relative strengths. The C Is spectrum exhibits only one sharp bulk peak for the clean Si-rich surfaces, This is different compared to earlier results from the same surfaces prepared h in situ heating only. The effects induced upon initial oxidation of these Si-rich surfaces are investigated, Recorded Si 2p spectra show only one suboxide. Si+1 and Si+2, for the polar (0001) and (MOT) surfaces, respectively besides the fully developed Si,4 oxide (SiO2). For the nonpolar Surfaces two suboxide. Si+1 and Si+2. are observed, Similarities and differences compared to earlier findings are discussed. Valence band spectra collected from clean surfaces, before Si deposition, are presented for the nonpolar surfaces. The presence of a sharp structure at binding energies of about 2.0 and 2.7 eV for the (1010) and the (1010) surfaces, respectively is observed. This structure shows no dispersion with photon energy and is very sensitive to oxygen exposures and is therefore tentatively suggested to be a surface resonance state.