The Orientation Transition and Control of REBaCu₃O_y Films Grown by Liquid Phase Epitaxy

Abstract

Liquid phase epitaxy (LPE)-processed REBa2Cu3O7‑δ films, which possess single-crystalline properties, are of great significance to fundamental superconductor studies and practical applications. Performances of these films are related to their crystallographic orientations due to the notable anisotropy of coherent length along the a (and/or b) axis and c axis. Recently, an increasing number of experimental outcomes have proven that this preferential orientation is strongly dependent on the growth conditions. Based on those systematic results, the origin of crystallographic orientations is satisfactorily understood. Furthermore, attention has been directed toward tuning supersaturation for oriented film control, such as the pure a-axis oriented film (a-film), the pure c-axis oriented film (c-film), and some distinctive composite structures with superior performance for device applications. In order to provide universal guidance for artificial microstructure manipulation in LPE and significant insights for the development of film preparation, the mechanism of the a-/c-film formation related to thermodynamic and kinetic factors as well as the oriented growth control have been discussed in this review. Furthermore, the whole evolution model of oriented structures is also established, which may help researchers to better understand the films growth mechanism. Finally, the current challenges and future outlook on this flourishing topic have been suggested.