Superconducting characteristics of YBCO films

An investigation has been made of superconducting YBa₂Cu₃O_y (YBCO) thin films, which were prepared with two synthetic processes using RF-magnetron sputtering: (a) deposition at low substrate temperature with postannealing at around 900°C, and (b) deposition at high substrate temperature around 650°C with or without postannealing. High-T_c superconducting YBCO thin films were obtained with either process. The films prepared with process (a) had, however, poor J_c below 10 A/cm² at 77 K and their surfaces were rough. The films prepared with process (b) had higher J_c and smoother surfaces. Further improvement in surface morphology was made by raising substrate temperature to 700°C at the start of the deposition