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

本文尝试用离子束辅助离子束溅射的方法在低生长温度下制备铋高Tc超导薄膜。为此，研制了一种离子束辅助离子束溅射的薄膜加工设备。在真空室中设置有溅射离子枪、辅助离子枪、靶架和衬底架。在衬底附近设置了一个氧气喷嘴。制备了BiSrCaCuO体系薄膜，并研究了薄膜性能与衬底温度（Ts）和氧压(P)的关系。当P=1X10^<-4> Torr时，在Ts=600-700 C下制备的薄膜中，Bi和Cu的电阻率较差，在rt处绝缘。当P=3X10^<-4> Torr时，薄膜具有导电性，电阻率为1-100 ω cm。当P=3X10^<-4> Torr时，在薄膜生长过程中，当O+辅助离子照射时，薄膜的电阻率为几ω cm，并表现出2201相的XRD峰。然而，它们的组成大约是2212。离子助剂具有表面迁移和强氧化作用，抑制铋的蒸发，有利于形成晶体结构。当制备的薄膜在800℃下退火时，其XRD峰为2201和2212相，并表现出超导转变。当温度为700℃时，薄膜的起始温度为91 K。对于没有辅助的薄膜，没有观察到相同的退火效果。从而阐明了离子辅助晶体生长的潜在作用。

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.