Photoemission studies of oxide superconductors

A procedure has been developed for preparation of clean surfaces of oxide superconductors for study by electron spectroscopy. This involves annealing ceramic or thin film samples under an oxygen atmosphere in a preparation chamber that is an integral part of the spectrometer UHV system. The technique has allowed us to obtain high quality spectroscopic data from YBa,Cu,O,-, , Bi2Sr2Can-,Cun04+2n (n = 2, 3) and La2-,Sr,Cu04. Our results are considered in relation to other contemporary work. Current areas of controversy will be highlighted, including a discussion of Fermi edge and satellite structure in valence region spectra and evidence for mixed valency in Cu : 2p and 0 : 1s core regions.