Photoemission study of the Si(111)3×1-K surface

Abstract

Surface electronic states of the Si(111)3\ifmmode\times\else\texttimes\fi{}1-K surface are studied by means of angle-resolved ultraviolet photoelectron spectroscopy along the [112\ifmmode\bar\else\textasciimacron\fi{}] and the [101\ifmmode\bar\else\textasciimacron\fi{}] directions. It is found that the ${\mathrm{S}}_{1}$ state (\ensuremath{\sim}0.2 eV below the Fermi level) of the 7\ifmmode\times\else\texttimes\fi{}7 surface disappears and surface states ${\mathrm{S}}_{2}^{\ensuremath{'}}$ and ${\mathrm{S}}_{3}^{\ensuremath{'}}$ appear near the binding energy of \ensuremath{\sim}0.9 and \ensuremath{\sim}1.8 eV below the Fermi level in the spectra of the Si(111)(3\ifmmode\times\else\texttimes\fi{}1)-K surface. Hence, the Si(111)3\ifmmode\times\else\texttimes\fi{}1-K surface is no longer metallic like the Si(111)7\ifmmode\times\else\texttimes\fi{}7 clean surface but is semiconducting. The saturation coverage of K on the Si(111)3\ifmmode\times\else\texttimes\fi{}1-K surface is estimated to be 13 ML from comparison of the Si LVV Auger spectrum and the K 2p x-ray-photoemission-spectroscopy peak intensity ratio to that of the Si(111)\ensuremath{\delta}7\ifmmode\times\else\texttimes\fi{}7-K surface. From these results, we suggest a surface geometrical structural model for the Si(111)3\ifmmode\times\else\texttimes\fi{}1-K surface.