HIGH-TEMPERATURE IN-SITU GROWTH BY CATHODIC SPUTTERING OF FULLY OXYGENATED YBACUO THIN-FILMS

The structure and oxygen content of YBaCuO thin films were measured at room temperature combining XRD analysis of individual YBaCuO grains w ith recently developed IBA techniques. As a function of the conditions of the sample cooling (dT/dt, pO(2)), the similar to 500 nm thick YBa CuO samples grown on LaAlO3 single crystal substrates can exhibit eith er orthorhombic (ORT) or quasitetragonal (TETR) structure. The former is obtained by low cooling rates at high oxygen pressure (0.2-latm) wh ereas the later needs a high cooling rates (greater than or equal to 1 00 degrees C/min) and can be performed at low oxygen pressure. Both ty pe of samples are fury oxygenated (similar to O-7) YBaCuO compounds wi th Tc onset of 91 K and Delta Tc approximate to 1K. The resistivity of the (TETR) compound is about 3 times higher than that of the (ORT) on e and the intercept of the rho(T) curve crosses the axis of the resist ivity at a large positive value, as expected for the tetragonal compou nd of the 1-2-3 family. From these observations and following kinetics considerations, we postulate that the formation of YBaCuO thin films with fully oxygenated (similar to O-7) tetragonal structure takes plac e during the ''in situ'' high temperature growth by cathodic sputterin g.