Single domain high T c La2−xSrxCuO4 films with tilted CuO2 planes

Abstract

The two fold degeneracy inherent to epitaxial growth of high T_c films on (101) perovskite substrates has been removed successfully. This is demonstrated by single domain, (103) oriented La_2−xSr_xCuO₄ films of 0.04≤x≤0.34 on vicinal (101) SrTiO₃ substrates using 90° off‐axis sputtering. (101) substrates that have the surface normal rotated about [010] by 0.5°–3.5° produced essentially single crystal films with the c‐axis direction determined by the sense of the miscut. Misoriented antidomains (103)’ have been eliminated effectively to a percentage less than 1 part in 10⁴. The mechanism for symmetry breaking is understood on the basis of a surface step model in which the energetics promoting single domain growth is derived from nucleation and epitaxy on the (001) face found at surface steps of vicinal substrates. Furthermore, the incommensuration of the c axis interplanar spacings with the a, b, plane lattice parameters in the La_2−xSr_xCuO₄ structure provides a natural selection of (103) domains over (103)’ domains. The model predicts the application to other high T_c materials such as the Bi₂Sr₂Ca_nCu_n+1O_x, and the Tl₂Ba₂Ca_nCu_n+1O_x families.