Potassium adsorption on the polar NbC(111) surface: angle-resolved photoemission study

Abstract

Angle-resolved photoemission spectroscopy with synchrotron radiation has been used to study the adsorption mechanism of K on a NbC(111) surface. The coverage-dependent measurements of the valence-band region show that the K 4s state is hybridized with the surface states at around the Fermi level on the NbC(111) surface to form bonding and antibonding states. In the initial stage of adsorption, only the bonding state, mainly composed of Nb 4d states, is occupied, which results in a polarized overlayer. The antibonding state, mainly composed of K 4s states, becomes occupied after depolarization to form a metallic overlayer. The overall results are compatible with the adsorption model proposed by our previous core-level photoemission study; the K 4s state interacts with the surface states on the NbC(111) surface, and the adsorption proceeds via a polarization-depolarization transition.