Defects of YBCO films grown by liquid-phase epitaxy on NdGaO3

Defects observed on a- and c-oriented YBa2Cu3O7-x(YBCO) films grown by liquid-phase epitaxy (LPE) on (1 1 0) and (0 0 1) NdGaO3 (NGO) are discussed. The orientation-dependent cracking and twinning of the films is shown and related to the misfit-induced strain. The film thicknesses and crack distances of LPE-grown YBCO layers were measured by Nomarski microscopy and by scanning electron microscopy. For a-oriented films on(1 1 0) NGO, with an estimated uniaxial effective him strain of 1.8% (c(f)parallel to d(s)), a good fit with theory is found. For c-oriented layers on (1 1 0) NGO, an effective strain of 0.08% (a(f)/b(f)parallel to d(s)) is found. This value is lower than that predicted from the theory and this might be explained by the strain relaxation due to to twinning. (C) 1999 Elsevier Science B.V. All rights reserved.