GROWTH-MECHANISM OF A-AXIS 123 THIN-FILMS ON LAALO3 WITHOUT PBCO INTERFACE

The growth mechanism of a-axis ''123'' thin film on LaAlO3 has been studied by HREM. At 650-degrees-C, a tetragonal marquetry-like structure is rapidly formed with the a*- and c*-axes of the perovskite parallel to the a*- or (b*-) axis of the substrate. At 780-degrees-C, large domains of ill-crystallized ''123'' phase form with the orthorhombic symmetry. After a slow cooling down under an oxygen pressure of 300 mbar, the film quality is improved and the a-axis orientation remains. When the oxygen introduction and cooling down processes are not optimized, a growth with the c-axis perpendicular to the substrate is observed. A model is proposed for the description of this mechanism requiring small displacements only at the level of one or two interatomic distances.