Orientation and Crystal Growth Mode in Sm_1+xBa_2-xCu₃O_y Films Prepared by a Low Temperature Growth Technique

Abstract

We have reported high-J_c Sm_1+xBa_2-xCu₃O_y (SmBCO) films prepared by a low-temperature growth (LTG) technique. Despite the low-substrate temperature, the LTG-SmBCO films showed complete c-axis orientation and cube-on-cube texture. In addition, the LTG-SmBCO films showed a J_c of 0.28 MA/cm² (77 K, B//c, B=5 T), because these included high-dislocation densities and nanosize low-T_c particles. In this study, we discuss the mechanism of c-axis orientation and crystal growth for high-J_c LTG-SmBCO films. We newly suggest a model for “Nucleated growth on c-axis oriented Seed layer (NCS)" to understand the c-axis orientation mechanism for LTG-SmBCO films. Based on the NCS model, when the LTG-SmBCO films nucleated on a seed layer have two-dimensional (2D) nuclei with a 1 unit SmBCO step cell height, the interfacial energy between the nucleus and the seed layer and the critical Gibbs free energy of the nucleus are lower than those of PLD-SmBCO films. Therefore, the LTG-SmBCO films show high crystal quality and a wide processing window for biaxial orientation. We suggest that the LTG technique is effective for not only increasing J_c in magnetic fields, but also improving the processing window and crystal quality.