Fabrication of high sensitivity 3D nanoSQUIDs based on a focused ion beam sculpting technique

In this paper a nanofabrication process, based on a focused ion beam (FIB) nanosculpting technique, for high sensitivity three-dimensional nanoscale superconducting quantum interference devices (nanoSQUIDs) is reported. The crucial steps of the fabrication process are described, as are some peculiar features of the superconductor-normal metal-insulator-superconductor (SNIS) Josephson junctions, which may useful for applications in cryocooler systems. This fabrication procedure is employed to fabricate sandwich nanojunctions and high sensitivity nanoSQUIDs. Specifically, the superconductive nanosensors have a rectangular loop of 1 × 0.2-0.4 ?m2 interrupted by two square Nb/Al-AlO x /Nb SNIS Josephson junctions with side lengths of 0.3 ?m. The characterization of a typical nanoSQUID has been carried out and a spectral density of magnetic flux noise as low as 0.8 ??0 Hz-1/2 has been measured.