Photoemission investigations of the high-Tc superconductor BiSrCaCuO

Abstract XPS and UPS photoemission experiments on several multiphased samples of the high- T c superconductor BiSrCaCuO with a composition around Bi 2 Sr 2 CaCu 2 O 8+ x and zero resistivity below 77 K showed the following results: 1. (1) The samples are easily cleaned from carbonate contaminations by in situ scraping or UHV annealing at about 500°C without loss of the superconducting properties. 2. (2) The valence band spectra show a well defined Fermi edge with an intensity of about 0.01 as compared to the valence band maximum. The spectroscopic valence band features correlate only qualitatively to recent band structure calculations. 3. (3) The XPS core level spectra of the Bi-4f, Sr-3d and Ca-2p levels show a single very well resolved spectrum. The Cu -2 p 3 2 spectrum has satellites, typical for Cu 2+ species as e.g. in CuO and a small shoulder at lower binding energies probably of unreacted Cu 2 O. The O-1s spectrum shows a well resolved line at 528.7 eV binding energy, with no significant contributions of a satellite at higher binding energies.