Superconducting and epitaxial (Tl,Pb)Sr2Ca1−xYxCu2O7 thin films by in situ deposition

We report the growth of thin films of (Tl,Pb)Sr2Ca1−xYxCu2O7 with x=0–0.2 by off-axis magnetron sputtering in the presence of thallium oxide vapor. The (Tl,Pb)Sr2Ca1−xYxCu2O7 films are highly c-axis oriented on the pseudocubic (100) surface of LaAlO3 or on (001)NdGaO3. The 〈100〉 axes of the films grown on LaAlO3 align to the pseudocubic 〈100〉 axes of the substrate while for films on NdGaO3 they are rotated 45° relative to orthorhombic 〈100〉 substrate axes. After an in situ heat treatment, undoped (Tl,Pb)Sr2CaCu2O7 films are superconducting at temperatures up to 82 K, compared with 85 K for the bulk material. Yttrium doping on the calcium site increased the transition temperature as expected. The highest transition temperature observed was 86 K for x=0.1 and 93 K for x=0.2.