Planar MoRe-based direct current nanoSQUID

We have developed planar nanoSQUID with nanobridge-type Josephson junctions based on the oxidation resistant and high Hc2 MoRe alloy. The objective of the research was to reduce size of the SQUID loop with the aim being to reduce magnetic flux noise and improve the spatial resolution of the SQUID sensors. Employing RF-magnetron sputtering, electron-beam lithography, and reactive ion etching in CHF3 + O2 plasma using Al hard masks, we have realized nanoSQUIDs with Josephson junctions in the form of 30 − 50 nm wide nanobridges and an effective magnetic flux capture radius of ~ 95 nm. The critical temperature of the fabricated devices was Tc = 7.9 K. The I(V)-characteristics demonstrated critical current I0 114 µA at 4.2 K and modulation period in magnetic fields of ~ 700 Oe.