The Influence of Nano-Dots Decoration on Substrates on Flux Pinning Strength in Thin Films

Nano-sized CeO₂ dots were deposited on (001) LaAlO₃ substrate by rf magnetron sputtering. After the processing of the artificial decoration defects on the substrate, 100-nm, 150-nm, 200-nm, and 400-nm-thick Tl₂Ba₂CaCu₂O₈ (Tl-2212) thin films were grown on it, using dc magnetron sputtering and post annealing process. AFM images showed that the CeO₂ nano-dots were distributed well on the substrate surface with 70 nm in diameter and 5 nm in height, and the density of nano-dots was 25±3 dots/μm². SEM images were used to observe the variations on film surface. Transport critical current density J_c was measured both on Tl-2212 film with nano-dots decorated substrate and untreated single crystal LaAlO₃ substrate. From the results, J_c values of Tl-2212 films with nano-dots decorated substrate were lifted significantly, and the pinning strength was improved on Tl-2212 films by nanostructure defects induced from nano-dots.