X-Ray Photoemission Study of 200angstroms Bi-Sr-Ca-Cu Oxide Thin Films

Core level spectra of Bi-Sr-Ca-Cu oxide thin films 200angstroms thick produced by RF magnetron sputtering on MgO substrates at room temperature have been measured. Since the films basically consist of only 6-7 units of the oxide layers, the importance of the surface sensitivity of photoemission is minimized and the electronic structure can be directly studied. The samples were annealed in oxygen at temperatures ranging from 600C to 870C, over which temperature range the thin films are converted from an amorphous insulating phase to an ordered superconducting phase with T sub c (R=0) at 60K. Regardless of the annealing temperature, the Cu 2p spectra of all films show satellite structure indicative of Cu sup 2+ states.