Parallel core and valence photoemission studies of nominal (Bi0.9Pb0.1)2Sr2Ca2Cu3O10+x

Clean surfaces of ceramic samples of the oxide superconductor (Bi0.9Pb0.1)2Sr2Ca2Cu3O10+x have been prepared by in situ annealing under pure oxygen at atmospheric pressure inside a UHV system. Scraping of these surfaces under argon is shown to re-expose contaminated grain boundaries, whilst oxygen annealing removes this contamination. Analysis of Pb 4f XPS peak shapes suggests that the metallic character of the Bi-O planes is enhanced by Pb2+ substitution for Bi3+. Ultraviolet photoemission spectra indicate some small changes in the valence band DOS from the Bi2(Sr,Ca)3Cu2O8+x superconductors; in particular, the density of states at Ef is significantly enhanced, as expected from the considerably higher Tc of these materials.