Oxygen post-annealing effects on critical current properties of PLD-ErBa2Cu3Oy films grown at several substrate temperatures

Abstract

We report the effects of oxygen post-annealing on critical current properties and normal state resistivities in ErBa2Cu3Oy/SrTiO3(Er123/STO) thin films fabricated in the substrate temperature range from 720°C to 780°C by pulsed laser deposition (PLD). Interestingly, for films fabricated below 760°C, the critical current density (Jc) increased by oxygen post-annealing process from 0.3–0.6×106Acm−2 to the order of 106Acm−2 for the as-deposited films despite critical temperatures (Tc) of ∼90K for both annealed and as-deposited films. In the 780°C-deposited film, Jc was not obviously enhanced. X-ray diffraction and measurement of normal state resistivities revealed that the PLD-Er123/STO films showed high-quality crystallographic and electrical properties in films deposited below 760°C. In high temperature resistivity measurements, the resistivity reduced with annealing time and showed a systematic change with changing oxygen partial pressure. These results strongly suggest that oxygen post-annealing is indispensable for improving Jc in 123 films fabricated through a non-equilibrium process such as the PLD method even though the as-deposited films show a Tc value of ∼90K.