Crystal growth of YBa₂Cu₃O_7-X thin films prepared by TFA-MOD method

We have investigated an epitaxial growth of YBa₂Cu₃O_7-X (YBCO) films on [001] SrTiO₃ substrates prepared by metal organic deposition (MOD) method using trifluoroacetate (TFA) solution. The YBCO films derived by this method have high J_C exceeding 5 MA/cm² at 77 K. We tried to clarify the growth mechanism of TFA-MOD YBCO films by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) from viewpoint of both macro and micro scales. We prepared partially transformed films by quench during high temperature annealing under the conditions at 730, 740, 750 °C, dew point = 20 °C, P(O₂) = 130 ppm, and gas flow rate = 1000 cc/min. In the growth stage, the integrated intensities of θ-_χ scans for the films increased with annealing time, and after more annealing, the integrated intensities decreased. SEM and TEM images indicated an existing of the pores in the films. Avrami plot was performed on the growing YBCO films, and the Avrami exponents were 1 < n < 2.