NQR: a non-destructive method for studying oxygen content and defects in YBa2Cu3O6+x superconducting thin films

Abstract NQR spectra of 63,65 Cu isotopes were measured in YBa 2 Cu 3 O 6+x thin films at 1.4 K, which were prepared by cathodic sputtering and chemical vapor deposition. By comparison with powder spectra, we show that the films obtained by cathodic sputtering are overdoped. We discuss the possible reasons of the lower T c commonly obtained in YBa 2 Cu 3 O 6+x thin films by comparison with powders and single crystals. Furthermore, we show that thin films synthesized by chemical vapor deposition could be affected by carbon retention.