Nucleation and growth of b-axis oriented PrBa2Cu3O7-x thin films on LaSrGaO4 (100) substrates

Good quality a-axis oriented thin films of YBa2Cu3O7-x may be grown by the use of a PrBa2Cu3O7-x (PBCO) layer as a template. Here we present a detailed study of the nucleation of the PBCO layer, explaining the orientations observed. It is determined that the wavy surface of a LaSrGaO4 (LSGO) (100) substrate consists of the {101} planes by observing cross-sectional transmission electron microscopy images of the interface between the PBCO film and the substrate. The images and selected area diffraction patterns show that a mixed c- and b-axis oriented PBCO layer was initially grown on the substrate, followed by pure b-axis oriented PBCO growth. We explain that the c-axis oriented growth is the result of the growth of the PBCO (019) planes on the LSGO (101) planes. We conclude that the nucleation and growth of the PBCO films at the initial stages depends on the crystallographic plane of the substrate surfaces, however, as the fi Im grows further, the kinetics of the deposition process favors b-axis oriented growth.