Low Temperature Film Growth of Epitaxial Bi High-Tc Superconducting Single Crystals by Ion Beam Assisted Ion Beam Sputtering

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I tried to prepare Bi high Tc superconducting thin films at low growth temperature by an ion beam assited ion beam sputtering. To attain this purpose, I made an equipment of thin film processing by the ion beam assisted ion beam sputtering. There arranged a sputter ion gun, an assist ion gun, a target holder and a substrate holder in a vacuum chamber. A nozzle of oxigen gas was set near the substrate. The films of BiSrCaCuO system were prepared, and dependences of film properties on the substrate temperature (Ts) and the oxygen patial pressure (P) were investigated. For P=1X10^<-4> Torr, Bi and Cu are poor in the films prepared at Ts=600-700 ﾟC and they are insulating at rt. For P=3X10^<-4> Torr, the films are conducting and have resistivity of 1-100 OMEGA cm. For P=3X10^<-4> Torr, when O+ assist ions are irradiated during the film growth, the films have the resistivity of several OMEGA cm and show XRD peaks of2201 phase. However, their composition is about 2212. The ion assisting has effects of a surface migration and a strong oxidation which suppres evaporation of Bi and facilitate to form crystal structure. When the films prepared by the assisting are annealed at 800 ﾟC , they show XRD peaks of 2201 and 2212 phases and show superconducting transition. The onset temperature is 91 K for the film for Ts=700 ﾟC . The same annealing effect is not observed for the films without the assisting. Therefore, the potential effect of the ion assisting on crystal growth is clarified.