POTASSIUM ADSORPTION ON THE POLAR NBC(111) SURFACE - CORE-LEVEL PHOTOEMISSION-STUDY

The potassium adsorption process on a NbC(111) surface has been studie d with core-level photoemission spectroscopy. The coverage dependence of the work function and the K 3p core-level photoemission spectrum re flects that adsorption proceeds via a polarization-depolarization phas e transition, which is brought about up to a coverage of 0.3 ML. A spe ctral line-shape analysis for the R 3p core-level peak has been perfor med, and it is proposed that the interaction between the K 4s orbital and the substrate Nb4d orbitals plays an important role in the initial stage to form the polarized K overlayer.