Development of electronic band structure of the K-adsorbed Si(111)7 × 7 surface

Abstract

Adsorption of K on the Si(111)7 × 7 surface has been investigated in the submonolayer coverage range at room temperature. The method of threshold photoemission spectroscopy using s- and p-polarized light excitation was employed for studying the evolution of surface electronic structure near the Fermi level, the work function and the ionization energy. A qualitative change in character of band structure has been observed, depending on K coverage. Suppression of metallicity of the Si(111)7 × 7 surface was found at the initial stage of K adsorption. One surface band A1 below the VBM was revealed at low coverage. Increasing K coverage has led to both the appearance of the K-induced band A2 and significant movement of the band towards the Fermi level. The K/Si(111)7 × 7 interface was found to be semiconducting-like up to saturation coverage. Near saturation, the Fermi level is seen to cross the K-induced band A2. Such surface band structure is identified as being metallic-like. Results indicate metallization via adlayer accompanied by Fermi level pinning.