Preferentially oriented epitaxial Y-Ba-Cu-O films prepared by the ion beam sputtering method

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Abstract
Preferentially oriented epitaxial Y‐Ba‐Cu‐O films were prepared on (100) SrTiO3 substrates by oxygen reactive ion beam sputtering. The epitaxial orientations were varied by controlling both substrate temperature and oxygen parital pressure. c‐axis oriented films tended to be formed at higher substrate temperatures (>620 °C) and lower oxygen pressures (−3 Torr). In contrast, a/c‐ and a‐axis oriented films were formed at lower substrate temperatures (3×10−3 Torr). The best Tc (end) of 82 K was observed in one of the c‐axis oriented film without post‐annealing. The tendency for preferential orientation can be well understood in terms of the lattice mismatch between the substrate and the film, the lattice constants of which depend on oxygen deficiency.