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The photoemission spectra with a sychrotron radiation of (3×1) Na adsorbed orderly and disor-derly on Si(lll)-7×7 surface are analyzed and compared with the spectra of clean Si(lll)-7×7 surface. Na atoms are not simply adsorbed on the adatoms or rest atoms. The formation of the Schot-tky barrier is decided by the interaction between Na and Si atoms and seem to bear no relation to the surface structure. The Schottky barrier height(SBH) from experimental data is agreement with the value estimated by MIGS theory.

We calculate the atomic and electronic structure of β-SiC(001)-(2×1) using augmented plane wave and local orbital (APW+LO) method. The calculated results show that the atomic structure of β-SiC(001)-(2×1) surface can be described by symmetrical Si dimmer model, which is different from the asymmetrical Si dimmer model of Si(001)-(2×1) surface. The bond length of Si dimmer of β-SiC(001)-(2×1) surface is 0.269 nm, which is larger than that of Si(001)-(2×1) surface. The calculated results of electronic structure show that a prominent density of states exists at the Fermi level, so β-SiC(001)-(2×1) surface has the characteristics of metal. There are four surface state bands in the gap. Among them, two occupied surface state bands have been confirmed by valence band spectra of synchrotron radiation photoelectron spectroscopy.