Fabrication of superconducting nanowire arrays by nano laser direct writing

We report on the fabrication of superconducting nanowire arrays through photothermal effects induced by nano laser direct writing (NLDW), with progressively reduced spacing between the laser paths. The superconducting nanowire arrays were fabricated on 50 nm-thick Nb films via sputtering deposition on high-resistivity silicon substrates. Large-scale fabrication of superconducting nanowire arrays using NLDW has advantages such as cost-effectiveness, efficiency, and design flexibility. Furthermore, the thermal effects induced the degradation of Nb films with narrowing spacing, which were analyzed using simulated temperature distribution, electron probe x-ray micro-analysis, and electrical transport measurements. Specifically, the critical point of spacing (6.7 pixels) was confirmed, at which the Nb nanowires exhibited resistive behavior at 4.0 K. Similar to the pattern overlap and multiple exposure techniques in semiconductor fabrication, by designing appropriate spacing, the width of the remaining functional Nb film could be reduced to several tens of nanometers or even down to a few nanometers. Compared with traditional micro–nano fabrication techniques such as electron beam lithography and focused ion beams, the NLDW technique provides a reliable, economical, and reproducible pathway for scaling up superconducting circuits, as well as an avenue to conduct nanoscale thermal engineering on superconducting materials for basic scientific studies.