Enhancement of critical current by post-annealing of thin YBCO films prepared by laser ablation from a nanocrystalline target

Influence of post-annealing oil surface morphology and superconducting prop erties of thin YBCO films prepared by laser ablation from a. nanocrystallin e target is investigated. Annealing of the films in slowly flowing oxygen a t the optimum temperature of 900 degrees C increases the superconducting tr ansition temperature T-c at best from 82 K (as-deposited film) to 90 K (ann ealed film). Also the critical current density rises remarkably during anne aling, reaching the value of J(c) approximate to 1.4 x 10(7) A/cm(2) at 77 It in zero magnetic field; A plausible mechanism is discussed for explanati on of these observations. The main surface defects found on the annealed fi lms are a few large particles and holes. Between these defects the rms smoo thness of the surface is 3.6 nm.