Effect of substrate surface modification using Ag nano-dots on the improvement of J c and microstructures in YBa2Cu3O7 thin films grown on LaAlO3 (100) by pulsed laser deposition

Abstract

YBa2Cu3O7 (Y123) thin films were grown by pulsed laser deposition (PLD) on LaAlO3 (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 Jc and microstructures in the Y123 films has been studied systematically. The results showed that at fixed physical deposition conditions Jc increased with the number of Ag shots, n. Zero field Jc at 77 K increased from 106 to 3.3 × 106 A/cm2, and from 1.5 × 107up to 4 × 107A/cm2 for 5 K as the number of Ag shots increased from zero to 150. However, a fluctuation of Jc 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 Jc enhancement.