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 x 0.2-0.4 mu m(2) interrupted by two square Nb/Al-AlOx/Nb SNIS Josephson junctions with side lengths of 0.3 mu m. The characterization of a typical nanoSQUID has been carried out and a spectral density of magnetic flux noise as low as 0.8 mu Phi(0) Hz(-1/2) has been measured.