Evolution of the implanted 18O concentration distribution in a YBa 2Cu 3O 7−δ film during rapid thermal annealing

Abstract

To understand the behaviour of oxygen migration in YBa 2Cu 3O 7−δ (YBCO) films during rapid thermal annealing (RTA), a c-axis oriented YBCO film (800–900 nm) was implanted, at room temperature, with 200 keV 18O + to a dose of 5 × 10 16 18 O +/cm 2 . After implantation samples were annealed, at various temperatures between 450 and 870°C for 2 min or 870°C for 20 s, in a RTA annealer, in a flowing natural oxygen ambient. 18O concentration versus depth profiles were obtained with an Atomika 6500 SIMS instrument, using a 10 keV Cs + primary beam. It is found that the implanted 18O plays a very sensitive role in monitoring the migration of oxygen within the film during RTA. There is clear evidence that RTA at 450°C for 2 min results in an obvious re-distribution of as-implanted 18O but only very small amount of oxygen isotopic exchange between the gas ambient and the implanted 18O. In this case, the retained dose is found to be ∼ 95.6% Q 0 (where Q 0 is the retained dose after implantation); whereas RTA at 870°C for 20 s results in a sufficient oxygen exchange between the gas ambient and the implanted 18O, with the retained dose being smaller than 1% Q 0. Practical RTA conditions for annealing of irradiated YBCO films are discussed.