Angle-resolved photoelectron-spectroscopy study of the Si(001)2 x 1-K surface.

Angle-resolved ultraviolet photoelectron spectra for the Si(001)2\ifmmode\times\else\texttimes\fi{}1-K surface have been measured as a function of K coverage. It is found that the Si(001)2\ifmmode\times\else\texttimes\fi{}1-K surface is semiconducting at saturation K coverage, in contrast to previous interpretations of electron-energy-loss spectra based on a metallic Si(001)2\ifmmode\times\else\texttimes\fi{}1-K surface. It is further inferred that the saturation coverage of K for the Si(001)2\ifmmode\times\else\texttimes\fi{}1-K surface is one monolayer instead of half a monolayer as generally assumed for alkali-metal/Si(001) surfaces.