Electronic structure of Si(111)-Cl by angle-resolved secondary emission and electron energy loss

Abstract

Angle-resolved secondary emission from the Si(111)-Cl(7×7) system shows strong evidence for a series of resonances near $k_{\parallel }=0\mathrm{}$ at 4.6±0.1 eV above the vacuum level, with evidence for other resonances at $k_{\parallel }=0\mathrm{}$ at 2.6±0.1 eV and about 7 eV. Using the ionization potential of this surface determined from photoemission measurements of other workers, these data are found to be in excellent agreement with predictions of calculations by Schlüter and Cohen. Angle-resolved energy-loss spectra, taken with the effective primary beam emerging at an angle of 77° with respect to the surface normal, show no angle-dependent structure, indicating that the transitions observed are from flat occupied bands, i.e., localized states. The peak in the loss spectra at 8.7±0.1 eV, apparently mainly due to transitions involving $p_z$ orbitals, is compared with predictions of both the tight-binding calculation reported by Pandey, Sakurai, and Hagstrum, and the pseudopotential calculation of Schlüter and Cohen.