Photoemission Study Of The Surface Chemistry And The Electronic Structure Of Copper Oxide Superconducting Thin Films

We report our experimental results of the surface chemistry and the electronic structure of YBa2Cu307_δthin film by photoemission study. An experimental technique has been successfully used to clean superconducting thin films for photoemission experiments, while still preserving the superconducting properties of the films. The photoemission spectra obtained are consistent with our earlier results from bulk ceramic samples. This technique is then applied to study the surface chemistry of thin films under different annealing conditions. The films which have been ex situ post annealed and the films which have not been ex situ post annealed have been studied and compared. It is found that the oxidation of copper in the film strongly depends on the history of the thermal treatment of the film. On the other hand, Ba seems very stable in its doubly ionized state under all annealing conditions.