Formation of step-state bands on Si(111)3×3−Ag vicinal surfaces

Abstract

The effects of the step configuration and step density on the surface conductivity of Si(111) vicinal surfaces were investigated using an ultrahigh-vacuum electron microscope equipped with a surface conductivity measurement system. The Si(111)$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-Ag structure, which has a nearly-free-electron-like two-dimensional metallic surface state, was formed on the Si(111) terraces. The conductivity of the samples increased with increasing step density, which cannot be explained by assuming that steps form a barrier to electron conduction through the surface-state bands. The step density can affect the electronic band structure of the system through the formation of step-state bands or by changes in the band bending. The electronic band structure of the Si(111)$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-Ag surface prepared on vicinal surfaces was investigated by angle-resolved photoemission spectroscopy (ARPES) to examine these two possibilities. The ARPES investigation shows that the bulk bands are not modified and step-state bands are created on vicinal surfaces with high step densities. The electronic states of neighboring steps overlap to form step-state bands as the step-step distance is approached on a vicinal surface with high step density.