Importance of controlling the Tl-oxide partial pressure throughout the processing of TlBa2CaCu2O7 thin films

TlBa2CaCu2O7 (Tl-1212) superconducting films 5000--6000 A thick have been grown on LaAlO3 (100) substrates using oxide precursors in a closed two-zone thallination furnace. Tl-1212 films can be grown with transition temperatures ∼100 K, and critical current densities measured by magnetization of Jcm(5 K)>107 A/cm2 and Jcm(77 K)>105 A/cm2. Processing conditions, substrate temperatures and Tl-oxide source temperatures are found which result in smooth, nearly phase-pure Tl-1212 films. Variations in the respective temperature ramps of the Tl-oxide zone and the substrate zone can greatly influence resulting film properties such as microstructure, morphology, superconducting transition temperature, and critical current density. copyright 1995 American Institute of Physics