Photoemission study of the surface and bulk electronic structures of Si(111)7×7 and Si(111)≤3¯×≤3¯:Al

Abstract

Angle-resolved photoelectron spectroscopy has been used to study the surface and bulk electronic structures of Si(111)7\ifmmode\times\else\texttimes\fi{}7 and Si(111)\ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 :Al. For the Si(111)7\ifmmode\times\else\texttimes\fi{}7 surface we find three surface states at \ensuremath{\approxeq}-0.2 (${S}_{1}$), \ensuremath{\approxeq}-0.8 (${S}_{2}$), and \ensuremath{\approxeq}-1.8 (${S}_{3}$) eV. The ${S}_{3}$ surface state shows dispersion along the \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}--K\ifmmode\bar\else\textasciimacron\fi{} and \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}--M\ifmmode\bar\else\textasciimacron\fi{} lines in the 1\ifmmode\times\else\texttimes\fi{}1 surface Brillouin zone, with a bandwidth of \ensuremath{\approxeq}0.3 eV. For Si(111)\ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 :Al we find two surface-state structures ${A}_{1}$ and ${A}_{3}$ which are similar to the ${S}_{1}$ and ${S}_{3}$ structures for the 7\ifmmode\times\else\texttimes\fi{}7 surface. Structures due to direct transitions from the uppermost two valence bands are also identified in the spectra. Initial energy versus wave vector parallel to the surface, ${E}_{i}$(k${\ifmmode\bar\else\textasciimacron\fi{}}_{\mathrm{para}}$), dispersions are presented along the [112\ifmmode\bar\else\textasciimacron\fi{}], [2 1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{}], and [101\ifmmode\bar\else\textasciimacron\fi{}] azimuthal directions. The experimental dispersions for the direct transitions are in good agreement with calculated dispersions using a free-electron final band.