GROWTH-MECHANISM AND TYPICAL GRAIN-BOUNDARIES IN YBA2CU3O7-X THIN-FILMS GROWN ON MGO SUBSTRATES

Superconducting YBaCuO thin films grown in-situ by magnetron sputtering on mechanically polished (001) MgO substrates are examined by transmission electron microscopy. The films appear to be crystalline consisting of three main types of epitaxial domains 90-degrees-misoriented to each other, which causes the typical feature of these films, i.e., the high density of 90-degrees rotation twin-like boundaries. The surface of the films is not smooth resulting from the different thicknesses of the domains with different orientations. The microstructure of the films is explained by the growth rate anisotropy and the film nucleation peculiarities.