STRUCTURE AND COMPOSITION OF THE SURFACES OF SPUTTERED YBA2CU3O7-DELTA THIN-FILMS - AN XPS AND LEED STUDY

The surfaces of c-axis-oriented YBa2Cu3O7-delta (YBCO) thin films prep ared by DC-magnetron sputtering on SrTiO3(100) substrates were studied by means of X-ray photoelectron spectroscopy (XPS) and low-energy ele ctron diffraction (LEED). Since it was our intention to grow epitaxial multilayers the analysis was performed without exposing the samples t o ambient atmosphere in order to obtain in-situ information about the surfaces immediately after the deposition process. The LEED experiment proved that the single-crystalline structure of the films is maintain ed up to the surface. Additionally, the formation of superstructures o f the YBCO(001)2 x 2 type could be observed. Quantitative evaluation o f the XPS data showed the existence of a uniform termination on top of the surfaces of the single-crystalline YBCO films, which turned out t o be a BaO/CuO/BaO layer. The reactions of these surfaces with air wer e also examined.