Temperature-dependent performance of all-NbN DC-SQUID magnetometers

摘要

Integrated NbN direct current superconducting quantum interference device (DC-SQUID) magnetometers were developed based on high-quality epitaxial NbN/AlN/NbN Josephson junctions for SQUID applications operating at high temperatures. We report the current-voltage and voltage-flux characteristics and the noise performance of the NbN DC-SQUIDs for temperatures ranging from 4.2 to 9 K. The critical current and voltage swing of the DC-SQUIDs decreased by 15% and 25%, respectively, as the temperature was increased from 4.2 to 9 K. The white flux noise of the DC-SQUID magnetometer at 1 kHz increased from 3.9 μФ_0/Hz~(1/2) at 4.2 K to 4.8 μФ_0/Hz~(1/2) at 9 K with 23% increase, corresponding to the magnetic field noise of 6.6 and 8.1 fT/Hz~(1/2), respectively. The results show that NbN DC-SQUIDs improve the tolerance of the operating temperatures and temperature fluctuations in SQUID applications. Published by AIP Publishing.