Growth condition related orientation transition for YBa2Cu3O7−δ films on NdGaO3 substrate

Abstract

For comprehensive understanding, the crystallographic out-of-plane axis transition for YBa2Cu3O7−δ (YBCO or Y123) films grown on (110) NdGaO3 (NGO) substrate, using liquid phase epitaxy (LPE), was systematically investigated via changing flux composition, processing temperature and oxygen partial pressure. It is found that LPE films could grow, remarkably, in a wide temperature range between 24K above and 25K below the peritectic temperature (Tp). The unpredicted c-oriented films formed at the temperatures above Tp, is deduced to be attributed to the etch-back behavior, i.e., Nd partially dissolved from the NGO substrate into solution, which leads to a locally high supersaturation for facilitating film growth. Even more distinctively, decreasing from the high temperature in this wide range, the YBCO films characteristically experienced the orientation transitions, the double transition of the c-axis oriented→a/c-axis mixed→c-axis oriented in air, and a single evolution of the c-axis→a-axis in the pure oxygen atmosphere. By combining supersaturation with the NGO etch-back, and solute diffusion, the transition origin of the film orientation in various temperature regions was clarified.