Fabrication and Characterization of SQUIDs With Nb/Nb x Si1- x /Nb Junctions

Superconducting quantum interference devices (SQUIDs) with 3 μ m × 3 μ m or 4 μ m × 4 μ m self-shunted Nb/Nb x Si 1− x /Nb Josephson junctions are designed and fabricated. By adjusting the Nb content and thickness of the Nb x Si1− x barrier, the parameters of the SQUIDs can be easily tuned. The optimal parameters for the barrier are found to be a thickness of around 15 nm and 7% Nb content. The I–V curve, V–Φ curve, and noise spectrum are measured for the SQUID. The high frequency noise for the SQUID is only about several hundred nΦ0/√Hz. Another advantage for these devices is found, that it is not sensitive to the static electricity.