Supersaturation and crystallization behaviors of rare-earth based cuprate superconducting films grown by chemical solution deposition

Abstract

Chemical solution deposition is widely used in the preparation of rare-earth-based cuprate superconducting thin films, namely RExBa2Cu3O7-y (RE = rare earth element). The crystallographic orientation of the films is strongly dependent on the degree of supersaturation during crystallization. In this paper, we systematically studied the crucial factors affecting supersaturation, such as the type and stoichiometry of the rare earth element and the sintering temperature. Furthermore, the relationship between c-axis orientation and supersaturation was established. The results demonstrate that a small RE ionic radius (e.g., RE = Yb) and reduced rE-stoichiometry, studied on the example of yttrium, are beneficial for the growth of c-axis-oriented films at lower temperatures. In addition, a Y-O/Ba-Cu-O stacked-layer structure was proposed to regulate the diffusion distance to the reaction site. Compared with a Y-Ba-Cu-O single-layer, a c-axis orientation percentage of more than 40 % is achieved in the Y-O/Ba-Cu-O stacked-layer at even lower sintering temperatures. The results suggest that a low supersaturation is favorable to promote the growth of c-axis-oriented nuclei and therefore suppresses the growth of random orientations. This paper provides a new strategy to realize orientation modulation of rare-earth-based cuprate superconducting thin films by controlled chemical solution method.