Orientation relations and twinning in heterostructures YBa2Cu3Ox//NdGaO3 and YBa2Cu3Ox//CeO2//Al2O3

Epitaxial YBa(2)Cu(3)O(7)(-)x, (YBCO) thin films on (110) NdGaO3 and (100) CeO2 //(1102)Al2O3 substrates were studied with X-ray diffraction methods, orientation features of film twinning were determined. Films on both substr ates were mainly c-oriented with c = 11.67 Angstrom. Orthorhombic structure of NdGaO3 results in increase of the angle between (110) and (110) twinnin g planes in YBCO films to 90.20 degrees and in difference in volume of two twin domain systems. About 60% of YBCO film on CeO2//Al2O3 substrates show no twinning. The lattice direction (1102) of the Al2O3 substrate and (100) of the CeO2 film were inclined by 0.15 degrees; this inclination can result from high lattice mismatch between CeO2 film and Al2O3 substrate. The (001 ) direction of the YBCO film was inclined to (1102) Al2O3 direction only by 0.06 degrees. The spread of in-substrate-plane misorientation in CeO2 film of 1.65 degrees was also higher than that of the YBCO film (1.22 degrees). (C) 2000 Elsevier Science B.V. All rights reserved.