Surface-bulk uptake of hydrogen by niobium

Abstract
Photoemission spectroscopy and electrical resistivity have been used to measure both the surface and the bulk concentrations of H incident on Nb. It is difficult to understand both the uptake data and the surface-coverage results on the basis of a dilute hydrogen phase on the surface in equilibrium with the bulk. A model is proposed here in which at high surface concentration a hydride layer forms on the surface. Both the surface-coverage data and the bulk-uptake results are analyzed using this model.