SURFACE-ROUGHNESS AND HEIGHT-HEIGHT CORRELATIONS DEPENDENCE ON THICKNESS OF YBACUO THIN-FILMS

For high T-c superconducting multilayer applications, smooth interface s between the individual layers are required. However, in general, e.g ., YBaCuO grows in a 3D screw-dislocation or island nucleation growth mode, introducing a surface roughness. In this contribution we study t he surface layer roughness as a function of different deposition techn iques as well as deposition parameters. Special attention will be paid to the increase in film roughness with increasing film thickness. For these studies we used scanning probe microscopy. From these experimen ts, we obtained an island density decreasing with a square root depend ence on the film thickness. Furthermore, height-height correlations in dicate that the him growth can be described by a ballistic growth proc ess, with very limited effective surface diffusion. The correlation le ngths xi are on the order of the island size, inferring that the islan d size forms the mean diffusion barrier. This results in a representat ion of non-correlated islands, which can be considered as autonomous s ystems.