Effect of substrate surface modification using Ag nano-dots on the improvement of J{sub}c and microstructures in YBa{sub}2Cu{sub}3O{sub}7 thin films grown on LaAlO{sub}3 (100) by pulsed laser deposition

摘要

YBa{sub}2Cu{sub}3O{sub}7 (Y123) thin films were grown by pulsed laser deposition (PLD) on LaAlO{sub}3 (100) substrates whose surfaces were modified by a discontinuously layer of Ag nano-dots. The Y123 films were characterised by atomic force microscope, X-ray diffraction, scanning electron microscope, and DC magnetization measurements. Effect of substrate surface modification using various densities of the Ag nano-dots on the improvements of critical current density J{sub}c and microstructures in the Y123 films has been studied systematically. The results showed that at fixed physical deposition conditions J{sub}c increased with the number of Ag shots, n. Zero field J{sub}c at 77 K increased from 10{sup}6 to 3.3 × 10{sup}6 A/cm{sup}2, and from 1.5 × 10{sup}7 up to 4 × 10{sup}7 A/cm{sup}2 for 5 K as the number of Ag shots increased from zero to 150. However, a fluctuation of J{sub}c was observed for n < 60 at 77 and 40 K in both low and high fields. Detailed microstructure analysis revealed that ab misalignment was gradually improved as Ag nano-dots density gradually increased and believed to be responsible for the J{sub}c enhancement.