Surface-site-selective study of valence electronic states of a clean Si(111)-7<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>×</mml:mo></mml:mrow></mml:math>7 surface using Si<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>L</mml:mi><mml:mrow><mml:mn>23</mml:mn></mml:mrow></mml:msub><mml:mi mathvariant="italic">VV</mml:mi></mml:mrow></mml:math>Auger electron and Si 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>p</mml:mi></mml:mrow></mml:math>photoelectron coincidence measurements

Takuhiro Kakiuchi, Masashi Tahara, Shogo Hashimoto, Narihiko Fujita, Masatoshi Tanaka, Kazuhiko Mase, Shin-ichi Nagaoka

doi:10.1103/physrevb.83.035320

Valence electronic states of a clean Si(111)-7\ifmmode\times\else\texttimes\fi{}7 surface are investigated in a surface-site-selective way using high-resolution coincidence measurements of Si $p$$\mathit{VV}$ Auger electrons and Si 2$p$ photoelectrons. The Si ${L}_{23}$$\mathit{VV}$ Auger electron spectra measured in coincidence with energy-selected Si 2$p$ photoelectrons show that the valence band at the highest density of states in the vicinity of the rest atoms is shifted by \ensuremath{\sim}0.95 eV toward the Fermi level (${E}_{\mathrm{F}}$) relative to that in the vicinity of the pedestal atoms (atoms directly bonded to the adatoms). The valence-band maximum in the vicinity of the rest atoms, on the other hand, is shown to be shifted by \ensuremath{\sim}0.53 eV toward ${E}_{\mathrm{F}}$ relative to that in the vicinity of the pedestal atoms. The Si 2$p$ photoelectron spectra of Si(111)-7\ifmmode\times\else\texttimes\fi{}7 measured in coincidence with energy-selected Si ${L}_{23}$$\mathit{VV}$ Auger electrons identify the topmost surface components, and suggest that the dimers and the rest atoms are negatively charged while the pedestal atoms are positively charged. Furthermore, the Si 2$p$--Si ${L}_{23}$$\mathit{VV}$ photoelectron Auger coincidence spectroscopy directly verifies that the adatom Si 2$p$ component (usually denoted by ${C}_{3}$) is correlated with the surface state just below ${E}_{\mathrm{F}}$ (usually denoted by ${S}_{1}$), as has been observed in previous angle-resolved photoelectron spectroscopy studies.

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