Enhancement of Critical Current Density by Establishing a YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x Quasi-Trilayer Architecture Using the Sol-Gel Method

Abstract

We developed a solution-derived method to establish a YBa 2 Cu 3 O 7−x /LaAlO 3 /YBa 2 Cu 3 O 7−x quasi-trilayer architecture. Using the method, nano-scale pinning sites were induced into the quasi-trilayer architecture and yielded an apparent improvement in the in-field critical current density (J c ) of high-quality YBa 2 Cu 3 O 7−x (YBCO). The improvement in the in-field J c of the films was closely related to the thickness of the LaAlO 3 (LAO) interlayer. In this paper it is demonstrated that when the nominal interlayer thickness approximates 20 nm, which is slightly higher than the roughness of the YBa 2 Cu 3 O 7−x surface, the LaAlO 3 interlayer is discontinuous due to synchromesh-like growth of the LaAlO 3 layer on relatively rough YBa 2 Cu 3 O 7−x surface resulting from the mobility of the solution. Nanoscale defects, such as particles, some amorphous phases, and especially their concomitant lattice defects (such as stacking faults and plane buckling) arise in YBa 2 Cu 3 O 7−x layers. These nanoscale defects could play a role in flux pinning and thus enhancing J c . The effective non-vacuum solution to induce vortex pinning into YBa 2 Cu 3 O 7−x films could be a reference for the further design of an optimal pinning landscape for higher J c .

Trilayer Films of YBa2Cu3O7−x/LaAlO3/YBa2Cu3O7−x with Superconducting Properties Prepared via Sol-Gel Method

“…For the SIS-20 sample, the LAO film was too thin to cover the surface of the underlying YBCO layer completely, resulting in a direct contact between the upper and lower YBCO layers, thereby showing a superconducting performance similar to that of the single-layer YBCO film. However, the critical current density anisotropy in the SIS-20 sample was calculated to be 960, which is larger than that found for the SS sample, due to the heterogeneous distribution of the LAO interlayer [17]. Based on the superconducting properties of the YBCO layers in the sandwich structure, further I-V testing through the interlayer was carried out.…”

“…However, since the optimal process parameters for LAO film grown on LAO substate and on YBCO template are a little different, the process optimization will be done in the future to investigate if the results can be further improved. the growth thermal process, the LAO film could be epitaxial grown on YBCO layer by high resolution transmission electron microscope (HRTEM, JEOL, Tokyo, Japan) of the YBCO/LAO bilayer and YBCO/LAO/YBCO trilayer [17,19]. However, since the optimal process parameters for LAO film grown on LAO substate and on YBCO template are a little different, the process optimization will be done in the future to investigate if the results can be further improved.…”

“…In our previous work, trilayer structures of YBCO/LAO/YBCO were prepared via the sol-gel method, and their magnetic properties were characterized. It was found that the J c of the structure could be modulated by changing the thickness of the LAO layer [17]. Here, the electrical properties of the YBCO/LAO/YBCO trilayer structure are further analyzed, focusing on the modulation of the critical temperature T c and of the critical current I c by adjusting the thickness of the LAO middle layer.…”