Optical emission studies and preparation of high T_c TlCaBaCuO thin films

Thin films of TlCaBaCu oxide were sputter-deposited from dual oxide targets using a symmetrical RF diode sputtering system. Spatially resolved optical emission spectra obtained using a scanning optical fiber for CuO, BaO-doped CuO, and TlCaBaCuO targets suggest no significant bombardments of the growing film by energetic particles in the plasma, resulting in a film composition close to that of the sputtering targets used. The superconducting properties of these films were found to depend strongly on the post-annealing conditions as a result of a substantial loss of thallium during annealing. Highly textured c-axis oriented films comprised mostly of Tl2Ca2Ba2Cu3Ox, with a zero resistance Tc of 122 K have been synthesized on MgO substrates by annealing in a sealed quartz tube of films wrapped in gold foil with Tl2Ca2Ba2Cu3Ox powders. © 1989.