Preparation of YBa2Cu3O7 surfaces for photoemission studies by in situ oxygen annealing

Clean surfaces of ceramic samples of the oxide superconductor YBa2Cu3O7-x have been prepared in a UHV system by in situ annealing under pure oxygen at atmospheric pressure. Ultraviolet photoemission spectra from the oxygen-annealed surfaces are similar to those from cleaved single-crystal material. These results demonstrate that the surface of YBa2Cu3O7-x in equilibrium with the bulk of the material under the normal preparative conditions supports the same band structure as the cleavage surface. Core-level photoemission spectra from the oxygen-annealed surfaces are presented and briefly discussed.