Preparation of epitaxial Y-Ba-Cu-O thin films by pulsed ion-beam evaporation

Abstract

Summary form only given, as follows. YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (Y-123) high-T/sub c/ superconductor has excellent critical current density characteristics and thin films of Y-123 has been prepared by various methods. However, the deposition rate was limited and the increase in the deposition rate has been desired. A novel thin film deposition method has been developed, which is named as ion-beam evaporation (IBE). Extremely quick deposition rate can be characterized by this method which utilizes the high-density ablation plasma produced by a high power pulsed ion beam. In the present work, epitaxial Y-123 thin films have been successfully prepared by the IBE method. Deposition of Y-123 thin films has been carried out in a pulsed ion-beam generator ('ETIGO-II'). A voltage of 1 MV with the pulse width of /spl sim/50 ns was applied between the cathode and the anode. A polyethylene sheet (flashboard) was attached on the anode surface, worked as an H/sup +/ ion source. A Y-123 target was bombarded by a single shot of the ion beam. The ablation plasma was deposited on SrTiO/sub 3/ [100] substrates in vacuum (1 /spl times/ 10/sup -4/ Torr) and at room temperature. The thin films on the substrates were, annealed in flowing oxygen gas at 900/spl deg/C for 2 hours and 650/spl deg/C for 5 hours. The thin films were characterized with an X-ray diffractometer and a roughness tester. The XRD result for an annealed thin film indicated that all the peaks exactly correspond to the 001 reflections for a Y-123 phase. Since a [102] pole figure has four-fold symmetry, the Y-123 thin film was epitaxially grown on the substrate. The thickness of the Y-123 thin film was 0.3 /spl mu/m. From high-speed photographs of the ablation plasma, the plasma existed around the substrate for /spl sim/100 /spl mu/s. The instantaneous deposition rate of the film was 3 mm/s.