Structure of vapor-deposited yttria and zirconia thin films

The structures of thin films of zirconia and yttria, deposited by electron beam evaporation, have been examined by X-ray absorption fine structure (XAFS) analysis. It was found that the structure of the yttria film was similar to that of bulk yttria, which is a cubic oxide phase. The zirconia film, however, possessed a structure different from that of the bulk material. An analysis of the zirconia film data indicated a structure with a predominant tetragonal phase. Although lower coordination numbers were found in the films than in the standard powder specimens, it was not clear from the extended fine structure whether this deficit was due to film porosity observed in prior work or to the disorder that is generally observed in films. An analysis of the near-edge structure, however, suggested that porosity, rather than disorder, was present in the films. In addition, the K-edge positions observed for both the zirconia and the yttria films were higher in energy by approximately 3 eV than the corresponding K-edge in the powder specimens, indicating that the films may be more insulating than the standard bulk materials.