Infinite-layer copper-oxide laser-ablated thin films: Substrate, buffer-layer, and processing effects

Laser-ablation studies of highly-oriented thin films of the electon-doped infinite-layer copper-oxide compounds Sr1-xLaxCuO2 are reported. We observe significant variations in film properties with substrate or buffer layer material. X-ray diffraction; atomic force microscopy (AFM), Rutherford back-scattering (RBS), and electrical resistivity were used to characterize the films. Films were deposited on strontium titanaie (001) or on buffer layers of T'-phase copper oxides (Ln(2)CuO(4) with Ln = Pr, Nd, Sm), Sr3FeNb2O9, and La1.8Y0.2CuO4 on SrTiO3 (001). The in-plane lattice constants of such buffer layers (a = 0.390-0.400 nm) should provide the bond tension required for electron doping. Extremely flat, epitaxial buffer layers with X-ray rocking curves as narrow as 0.08degrees were obtained from stoichiometric targets of Ln(2)CuO(4); the other buffer layers yielded poor epitaxy. A linear dependence of infinite-layer c-axis plane spacing on substrate or buffer-layer in-plane a-axis lattice constant is observed.