Nanodimensional effects in the structure of epitaxial YBa2Cu3O7−y films

We have studied the structure of YBa2Cu3O7−y(YBCO) high-Tc superconductor films obtained by deposition for various times under otherwise identical conditions. Thin YBCO films prepared by the nonaxial laser shadow deposition technique are epitaxial and have microstrains below 1×10−3. The main factor determining variations of the unit cell parameter c in the films is the difference of the crystal block size 〈D〉 in the direction normal to the film surface, which reflects the nanodimensional effects known in oxides.