X-RAY PHOTOELECTRON SPECTROSCOPY STUDY ON THE HOLE STATES IN YBa 2 Cu 3 O 7 SUPERCONDUCTOR

XPS measurements have been performed on the orthogonal single phase YBa 2 Cu 3 O 7 superconductor. The higher valence-like state of Cu is observed clearly. The electronic states corresponding to the peaks in Cu 2p and O 1s XPS are discussed. It is suggested that the extra holes due to the excess oxygen are created on the O 2p orbit. The higher valence-like state of Cu corresponds to the combination of Cu 3d 9L and Cu 3d 10L 3 states.