Kinetics of YBa₂Cu₃O₇ film growth by postdeposition processing

The ex situ growth of thick textured YBa₂Cu₃O₇ films on SrTiO₃ substrates was investigated in order to find the factors, which influence growth kinetics. It was found that the growth rate of YBa₂Cu₃O₇ films remains constant during heat treatment and is proportional to the square root of the H₂O partial pressure in the processing atmosphere. Using transmission electron microscopy, we observed that the growth of the YBa₂Cu₃O₇ films proceeds from a thin, ∼7-nm-thick, layer of liquid located at the growth front. Chemical analysis of this layer and the adjacent material suggests that decomposition of an oxifluoride compound in the precursor film occurs at the liquid layer-precursor film interface. The rate of this decomposition reaction defines the growth rate of YBa₂Cu₃O₇. Using a simple model we show that rate of this reaction is limited by the out-diffusion of the decomposition product HF.