OXIDATION-KINETICS OF YBA2CU3O7-DELTA THIN-FILMS IN DIFFERENT OXIDIZING AMBIENTS

The effectiveness of different oxidizer gases (O, O2, N2O and NO2) for the post-growth oxidation of YBa2Cu3O7-delta (YBCO) thin films is investigated. In particular, the oxidation process in the presence of atomic and molecular oxygen is analyzed based on a simple kinetic model involving oxygen adsorption, desorption, and interface transfer steps. It is argued that the high oxidation capability of atomic O is a result of its direct adsorption with very high sticking probability. As a result, the thermodynamic stability range of YBCO at a particular temperature is shifted to significantly lower pressures in an atomic O plasma. On the basis of the known surface decomposition characteristics of N2O and NO2, the possible oxidation behavior of YBCO films in the presence of these gases is also discussed.