NbTiN SQUID-on-tip fabricated by self-aligned deposition using reactive DC magnetron sputtering

We fabricate superconducting quantum interference devices (SQUIDs) made of niobium-titanium nitride (NbTiN) thin films on the apex of sharp quartz capillaries. By incorporating reactive DC magnetron sputtering into the self-aligned deposition process for the SQUID-on-tip (SOT) fabrication, we produce NbTiN SOT devices with an effective diameter of ∼100 nm. The ø110 nm device has a superconducting transition temperature of 13.2 K, magnetic flux noise down to 0.7 μΦ0/Hz0.5 (4 K), and operating temperatures of 1.8–10 K. The developed technique enables the synthesis of nitride and other superconductors, thereby expanding the range of materials available for SOT devices.