Nucleation and growth of YBa₂Cu₃O_x on SrTiO₃ and CeO₂ by a BaF₂ postdeposition reaction process

The nucleation and growth of the c-axis-aligned YBa₂Cu₃O_x on SrTiO₃ and CeO₂, from precursor films, were studied by examining quenched and fully processed specimens using transmission electron microscopy techniques. The precursor films, a stoichiometric mixture of fine-grained Y, Cu, and BaF₂, were deposited using physical vapor deposition methods. An Y-Ba oxy-fluoride formed from the precursor contributed to the nucleation of YBa₂Cu₃O_x, while a liquid layer between the unreacted precursor and the YBa₂Cu₃O_x layer played an important role in the growth of YBa₂Cu₃O_x. However, the process of nucleation of YBa₂Cu₃O_x on SrTiO₃ and CeO₂ were significantly different.