Niobium nano-SQUIDs based on sub-micron tunnel junction fabricated by three-dimensional Focused Ion Beam sculpting

11th European Conference on Applied Superconductivity

Fretto, M.^1 ; Enrico, E.^1 ; De Leo, N.^1 ; Boarino, L.^1 ; Lacquaniti, V.^1 ; Granata, C.^2 ; Russo, R.^2 ; Vettoliere, A.^2

INRIM, Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce, 91, Torino

10135, Italy^1

Istituto di Cibernetica E. Caianiello Del Consiglio Nazionale Delle Ricerche, Pozzuoli (Napoli), Italy^2

关键词: Device reliability;    Electric transport characteristics;    Energetic ion beams;    External magnetic field;    Josephson tunneling;    Nanoscience applications;    Threedimensional (3-d);    Vertical configurations;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/507/4/042011/pdf
DOI  :  10.1088/1742-6596/507/4/042011

来源: IOP

【 摘 要 】

A three dimensional nano-SQUID (Superconducting Quantum Interference Device) has been realized in a vertical configuration (with the loop in the same plane of Josephson Tunneling Junctions, JTJs). The loop area is 0.25 μm2corresponding to a modulation period of about 5 mT, the square JTJs have a side length of 0.3 μm. Josephson junction's fabrication is carried out combining optical lithography to pattern trilayer and three dimensional (3D) Focused Ion Beam (FIB) sculpting technique to define the junctions' and the loop's areas. Two different ion etching processes were performed, perpendicular and parallel to the multilayer, resulting in a precise 3D structure. Finally, a standard anodization was performed to eliminate the unstructured surface material generated by the high energetic ion beam assuring high quality junctions. Electric transport characteristics of the nanodevice measured at T 4.2 K are reported, in particular the current-voltage characteristics and critical current vs external magnetic field. The high modulation depth of the critical current (up to 70% of the Icat zero magnetic flux) and the device reliability are very encouraging in view of nanoscience applications.