Improvement of critical current density and thermally assisted individual vortex depinning in pulsed-laser-deposited YBa2Cu3O7–delta thin films on SrTiO3 (100) substrate with surface modification by Ag nanodots

YBa2Cu3O7 films were fabricated by pulsed laser deposition on SrTiO3 (100) single-crystal substrates whose surfaces were modified by the introduction of Ag nanodots. The critical current density (Jc) was found to increase with the number of Ag shots. Zero-field magnetic Jc0 at 77 K increased from 8×105 up to 3.5×106 A/cm2 as the number of Ag shots increased from 0 to over 150 times. Microstructure investigations indicated that the crystallinity and the ab alignment gradually improved as the number of Ag nanodots increased. Thermally activated depinning of individual vortices is suggested responsible for a field-independent Jc plateau.