Kinetics characterization of YBCO thin films growth on LAO (100) single crystals by the TFA-MOD reaction

Abstract

We have studied in detail the kinetics parameters of the YBa2Cu3O7-x (YBCO) thin films growth on LaAlO3 (100) single crystals by the TFA-MOD method, using an i.n-situ fluoride selective electrode. We have considered: temperature, flow carrier gas rates and water partial pressure dependences in the reaction. Kinetics curves show that it exist an intermediate step before the YBCO formation. This step, which starts during the heating ramp (∼400°C) consists in a partial elimination of F from the BaF2 precursor to forms an oxyfluoride intermediate compound. The total YBCO formation appears at temperatures as higher as 700°C. We have found that at low flow carrier gas rates, the reaction is controlled by diffusion mechanisms and the apparent order of YBCO formation is n = 1 respect to the stirring rate, but at higher flow rates the YBCO formation is controlled chemically, then the apparent order is zero. The apparent reaction order of YBCO formation respect to the water pressure also has been studied.