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| Fabrication of Nb/Al-AlOx/Nb Josephson Junction Films by a Sputtering Process with a Long Target-substrate Distance |
| WANG Zhen-yu1,ZENG Jiu-sun1,GAO He2,WANG Shi-jian2,XU Da2,ZHONG Qing2,LI Jin-jin2,WANG Xue-shen2 |
1. College of Metrology and Measurement Engineering,China Jiliang University,Hangzhou,Zhejiang 310018,China
2. National Institute of Metrology,Beijing 102200,China |
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Abstract The fabrication of high-quality Nb/Al-AlOx/Nb trilayer films is crucial for quantum voltage standard chips and superconducting quantum interference devices based on superconductor-insulator-superconductor (SIS) type Josephson junctions. The effects of sputtering atmosphere and sputtering power on the structure, morphology and electrical properties of Nb and Nb/Al films are investigated for remote target-based distance DC magnetron sputtering process. The Nb film prepared with a Ar flow rate of 20mL/min, 0.53Pa, and 600W shows a stress close to zero pressure, a roughness of only 1.05nm, a superconducting transition temperature of 9.2K, and a residual resistance ratio of 5.33. The roughness of the 10nm Al film on 150nm Nb prepared at 0.53Pa, 450W is only 1.51nm and completely covers the underlying Nb film. The energy gap voltage of the Nb/Al-AlOx/Nb SIS junction prepared by these conditions reaches 2.6mV, indicating that remote sputtering process can achieve high-quality trilayer films required for the SIS junction process.
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Received: 26 April 2022
Published: 21 September 2023
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2023, Vol. 44 
