NQR: a non-destructive method for studying oxygen content and defects in YBa 2Cu 3O 6+x superconducting thin films

Abstract

NQR spectra of 63,65Cu isotopes were measured in YBa 2Cu 3O 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 2Cu 3O 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.