中文摘要：

用Mg/B多层膜退火的方法制备了一系列MgB2超导薄膜,研究了退火温度、退火时间和薄膜厚度对于MgB2薄膜性质的影响。厚度为250nm的Mg/B多层膜经400℃低温退火后已经生成超导相,此厚度薄膜750℃下退火20—30min实现最佳超导转变温度（Tc）。前驱膜分层厚度相同时,随着薄膜厚度减小MgB2薄膜Tc明显降低,而且较薄的膜Tc受退火温度影响更加明显。通过减小Mg/B多层膜分层厚度,制备的20nm厚MgB2超导薄膜在31K左右出现超导转变。

英文摘要：

The effects of annealing temperature, annealing time and film thickness on the properties of MgB2 thin films prepared by ex-situ annealing of Mg/B multilayer have been studied. The films with the thickness of 250 nm annealed at temperatures as low as 400 ℃ exhibited a superconducting transition. The optimal annealing condition of 250 nm thick MgB2 films regarding to the transition temperature, Tc, was 750 ℃ for 20—30 min. Tc became lower as the film thickness decreased and the Tc of thinner MgB2 films was influenced more greatly by the annealing temperature. With reducing the thickness of each single layer, we were able to fabricate the 20 nm thick MgB2 superconducting film with a Tonsetc of 31 K.