Roughness increase and dimensional transitions during the growth of GaBa2Cu3O6+y films on NdGaO3

The 123 compound films deposited by pulsed techniques are often characterized by large surface outgrowths that increase their roughness. They have exploited the high reproducibility of their pulsed e-beam channel spark ablation system to deposit a large number of GaBa2Cu3O6+y c-axis oriented films on NdGaO3 (110) substrates varying systematically the time of deposition quality of substrate and geometry of the target/shutter/substrate assembly. Scanning electron microscopy (SEM) and scanning force microscopy (SFM) studies show that the presence of outgrowths does not depend on the amount of large particles ablated from target but it is more intrinsic effect originated by the interaction between substrate defects and growing film. On a mesoscopic scale, the roughness of the films increases dramatically as a 2D-3D growth mode transition takes place. The occurrence of a dimensionality transition is clearly shown by the statistical treatment of SFM data