Abstract Nb/Al--AlO$_x$/Nb tunnel junctions are often used in the studies of macroscopic quantum phenomena and superconducting qubit applications of the Josephson devices. In this work, we describe a convenient and reliable process using electron beam lithography for the fabrication of high-quality，submicron-sized Nb/Al--AlO$_x$/Nb Josephson junctions. The technique follows the well-known selective Nb etching process and produces high-quality junctions with $V_m$=100 mV at 2.3 K for the typical critical current density of 2.2 kA/cm$^2$, which can be adjusted by controlling the oxygen pressure and oxidation time during the formation of the tunnelling barrier. We present the results of the temperature dependence of the sub-gap current and in-plane magnetic-field dependence of the critical current, and compare them with the theoretical predictions.
Received: 16 January 2008
Revised: 25 March 2008
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant Nos 10474129 and
10534060) and the Ministry of Science and Technology of China (Grant
Nos 2006CB601007 and 2006CB921107).
Cite this article:
Yu Hai-Feng(于海峰), Cao Wen-Hui(曹文会), Zhu Xiao-Bo(朱晓波), Yang Hai-Fang(杨海方), Yu Hong-Wei(于洪伟), Ren Yu-Feng (任育峰), Gu Chang-Zhi(顾长志), Chen Geng-Hua(陈赓华), and Zhao Shi-Ping(赵士平) Fabrication of high-quality submicron Nb/Al--AlOx/Nb tunnel junctions 2008 Chin. Phys. B 17 3083
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