High-performance of Superconducting Tunnel Junction for Terahertz Imaging

Nb/Al-AlOx-Al/Nb超导隧道结有望成为太赫兹成像的高灵敏度探测器。在使用高灵敏度探测器时，必须将亚间隙泄漏电流降低到BCS理论所指出的极限。为了获得亚隙漏电流较小的结，我们采用了一种新的方法，即电子束激发溅射技术，来制备由Nb层、Al层和隧道势垒组成的结。利用该系统研究了Nb层和Al层的沉积条件，以及Al层的刻蚀条件。Nb层的转变温度为9.3K，剩余电阻比大于3。制备的Nb/AlOx-Al/Nb约瑟夫森结具有带隙结构的SIS特性。

A Nb/Al-AlOx-Al/Nb superconducting tunnel junction is expected as a highly sensitive detector for Terahertz imaging. In the use of a highly sensitive detector, it is necessary to reduce the sub-gap leakage current to the limit indicated in the BCS theory. For obtaining the junction with small sub-gap leakage current, we take a new approach, that is, a electron-beam excited sputtering technique, for fabricating the junction consisted of Nb layer, Al layer and tunneling barrier. We studied the deposition conditions for both Nb and Al layers, and the etching condition for Al layer using this system. The transition temperature of the Nb layer and the residual resistance ratio have indicated 9.3 K and more than 3. Fabricated Nb/AlOx-Al/Nb Josephson junction has exhibited SIS characteristics with the gap structure.