Noise Evaluation of High Tc SQUID

Abstract

A high Tc DC Superconducting Quantum Interference Device (SQUID) with step edge junctions on SrTiO3(100) substrate have been fabricated. Noise components of four high Tc DC-SQUIDs have been evaluated. Intrinsic thermal noise levels of four SQUIDs have been estimated 7.9∼11.6μФ0/Hz1/2. 1/f noise comes from three noise sources, in-phase critical current fluctuation at two junctions, out-of-phase critical current fluctuation at two junctions and residual 1/f noise. In-phase and out-of-phase 1/f noise levels at 1Hz have been estimated 131∼781μФ0/Hz1/2 and 55.6~164μФ0/Hz1/2, respectively. In-phase 1/ f noise level was much larger than out-of-phase 1/f noise level, though two noise sources were deduced from the critical current fluctuation at two junctions. Residual 1/f noise levels have been estimated 19.6 ∼43.2μФ0/Hz1/2 and relatively smaller than the in-phase and out-of-phase 1/f noise levels.