多层膜外退火方法制备MgB_2超导薄膜

Fabrication of MgB_2 films via multilayer ex-situ annealing

报道了利用电子束蒸发的Mg/B多层膜作为前驱体,然后退火制备MgB2薄膜的工作.实验中发现,采用翻转膜面的退火处理方式可以有效地避免降温过程中Mg蒸气在薄膜表面形成的颗粒凝结,由此稳定地实现了面积为10mm×10mm,均匀、平整的超导薄膜的制备,Tc达35K,转变宽度为0·8K,在5μm×5μm的区域内薄膜的平均粗糙度小于10nm.为了便于后续器件制作过程中的微加工工艺,研究了膜厚小于1000时薄膜的成相规律,发现当样品厚度减薄后,Tc会有明显降低.通过调整前驱薄膜中的不同分层厚度,仍可实现转变温度达30K以上、厚度约600的MgB2薄膜,在20K时的临界电流密度为2·4×106A/cm2.

We fabricated superconducting MgB2 films with Mg/B muhilayer precursors followed by ex.situ annealing. Different ways of samples＇ placement have been tried, and we found that turning over the samples can effectively removed the particles of Mg condensed on the film surface. The Tc of the films was about 35K with a transition width of 0.8K. The surface is quite smooth, having a roughness of 10 nm in an area of 5 μm × 5 μm. When the thickness of the film is less than 1000A°, the Tc is significantly reduced. With the different configurations of the muhilayer precursor, the Tc of a 600A°-thick film can be optimized to 32K and the Jc is 2.4 × 10^6A/cm^2 at 20K.