Oxygen content and disorder in a-axis oriented YBa2Cu3O7−δ thin films

Using results of Raman spectroscopy, it is shown that the transition temperature Tc (R=0) of a-axis oriented YBa2Cu3O7−δ thin films strongly depends on the disorder in the oxygen sublattice. Regardless of deposition temperature Td, the films have an oxygen deficiency δ<0.1. However, at low Td, films show Tc≊50 K and a significant disorder in the distribution of chain and/or apex oxygen atoms. Using a template growth procedure we show that, at a sufficiently high Td, the oxygen disorder vanishes and Tc≳80 K, although the crystalline disorder, measured by the width of the (200) x-ray rocking curve, is increasing with Td.