Identification of chemical and structural impurities in YBa2Cu3O7-δ films by Raman spectroscopy

Raman spectroscopy has been applied to the identification of chemical and crystal structural impurities on the surfaces of YBa2Cu3O7-delta (YBCO) films. The surfaces of the two YBCO films studied have been shown to contain significant a-oriented components. Film A was prepared at a higher temperature than film B, with oxygen partial pressure remaining about the same. Compared with film A, film B presented a more uniform and shiny surface when observed with the naked eye. On film A, the surface was decorated by mutually perpendicular or parallel strings of beads (or particulates), while on film B, the particulates were more randomly distributed. The particulates were found to be BaCuO2, but the bead strings were mixtures of BaCuO2 and Ba2Cu3O5.9, grown concurrently with YBCO during vacuum deposition. (C) 1998 Published by Elsevier Science B.V. All rights reserved.