Site-specific X-ray absorption of twin-free (105) YBa2Cu3O7-delta films

O 1s and Cu 2p near-edge X-ray absorption fine structure (NEXAFS) spectra f rom highly oriented YBa2Cu3O7-delta (YBCO) films are compared to establishe d spectra from detwinned single crystals. The (105) orientation of the film s enables nearly twin-free growth and allows to investigate with NEXAFS the unoccupied electronic structure for all three polarizations E parallel to a, E parallel to b, and E parallel to c directly. While the Cu 2p spectra a re very similar to those of the single crystals, the O 1s spectra of the fi lms exhibit differences which can be traced to a substrate contribution. Th e YBCO film spectrum can be extracted from the data by an extended self-abs orption correction.