Preparation of REBa 2Cu 3O 7− x films grown by metal trifluoroacetate precursors

Abstract

Metal organic deposition (MOD) process using metal trifluoroacetate (TFA) precursors was applied to the NdBa 2Cu 3O 6+ y (Nd123) and the T c dependence of experimental conditions such as oxygen partial pressure ( P O 2 ) and substrate temperature ( T s) for annealing was investigated. Thin films grown on single crystal SrTiO 3 at T s=800°C under P O 2 =3×10 −4 atm showed a T c0 of 89 K. However, from the results of TEM-EDS measurements, the substitution value of x in Nd 1+ x Ba 2− x Cu 3O 6+ y increased from the substrate toward the surface in the film. These experimental results could be explained thermodynamically by the following model. The basic idea of our model is that the Ba potential is changed by coarsening of BaF 2 during the annealing for the growth. This model predicts that the small substitution value can be obtained with a higher growth rate of the Nd123 phase under low P O 2 .