Metal-to-non-metal transitions in high-temperature oxide superconductors monitored by photoelectron spectroscopy

Abstract

Metal-to-non-metal transitions induced in Bi–Sr–Ca–Cu–O by cation substitution and in Y–Ba–Cu–O by oxygen deficiency are used to show that changes in the Cu 2p signature in X-ray photoemission may be correlated with the changes in the hole doping level on the Cu–O₂ planes of these high-temperature superconducting oxides. Parallel core and valence studies of the transition in the Bi–Sr–Ca–Cu–O material suggest that some of the introduced holes may be present on the Bi—O planes in the superconducting state.