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

Abstract Defects observed on a - and c -oriented YBa 2 Cu 3 O 7− x (YBCO) films grown by liquid-phase epitaxy (LPE) on (1 1 0) and (0 0 1) NdGaO 3 (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 film strain of 1.8% ( c f ||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 ||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 twinning.