Surface 4f Level Shift in Yb Metal Studied by ARUPS, Hydrogen and Oxygen Exposures, and Work Function Measurement

抄録

Angle-resolved UPS spectra of 4f levels of Yb metal measured as a function of electron take-off angles have given a direct confirmation that satellite peaks of the 4f levels are due to the surface Yb atoms. Upon oxygen exposure, these surface components of the 4f levels do not show any preferential reduction in intensity and the work function decreases. These suggest the diffusion of adsorbed oxygen atoms underneath the Yb surface. By a mass analysis with hydrogen exposure to the Yb surface, it has been found that the surface is hydrogen free even though the evaporated Yb film contains hydrogen in the bulk. These facts lead to the interpretation that the surface 4f level shift in Yb metal is not hydrogen-induced but intrinsic.