1. Modulation depth of series SQUIDs modified by Josephson junction area*
- Author
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Wei Chen, Kamal Ahmada, Jie Liu, Zhang Ying Shan, Zheng-Wei Li, Jian She Liu, He Gao, and Gang Li
- Subjects
010302 applied physics ,Transimpedance amplifier ,Josephson effect ,Materials science ,business.industry ,Amplifier ,General Physics and Astronomy ,01 natural sciences ,law.invention ,SQUID ,Pi Josephson junction ,Amplitude modulation ,law ,Sputtering ,0103 physical sciences ,Optoelectronics ,010306 general physics ,business ,Electrical impedance - Abstract
The superconducting quantum interference device (SQUID) amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlO x /Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method. Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlO x /Nb trilayer. In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.
- Published
- 2017
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