TWINNING ORIENTATION IN YBA2CU3O7-X FILMS DEPOSITED ON YALO3 SUBSTRATES

An x-ray diffraction study of YBa2Cu3O7-x (YBCO) films deposited on YA lO3 (001) substrates by metal organic chemical vapor deposition is rep orted, The twinning orientation of YBCO on YAlO3 is compared to the on e observed for films deposited on MgO (001), SrTiO3 (001), and LaAlO3 (012) substrates. The phi scans performed on hhl type reflections and the grazing incidence x-ray diffraction on the 020/200 reflections of YBCO reveal a particular epitaxial relationship on YAlO3: there is onl y one twinning direction relatively to the substrate. The [110] and [1 (1) over bar 0] directions of YBCO are aligned with the [010] directi on of YAlO3. This twinning geometry may be explained by coherency stra ins. (C) 1996 American Institute of Physics.