CATION DISORDER AND GAS-PHASE EQUILIBRIUM IN AN YBA2CU3O7-X SUPERCONDUCTING THIN-FILM

YBa2Cu3Oy-x superconducting thin films have been grown by in situ off- axis rf sputtering with varying oxygen pressure, Ba/Y ratio in a targe t, and deposition temperature. With decreasing oxygen pressure, increa sing Ba/Y ratio, increasing deposition temperature, the critical tempe rature of the thin films decreased and the c-axis length increased. Th e property change of films with the variation of deposition variables has been explained by a gas phase equilibrium of the oxidation reactio n of Ba and Y. Applying Le Chatelier's principle to the oxidation reac tion, we were able to predict the relation of deposition variables and the resultant properties of thin films; the prediction was in good ag reement with the experimental results. From the relation between the t hree deposition variables and gas phase equilibrium, a 3-dimensional p rocessing diagram was introduced. This diagram has shown that the opti mum deposition condition of YBa2Cu3O7-x thin films is not a fixed poin t but can be varied. The gas phase equilibrium can also be applied to the explanation of previous results that good quality films were obtai ned at low deposition temperature using active species, such as O, O-3 , and O2+. (C) 1997 Elsevier Science B.V.