Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist

Abstract

We performed comparative experimental investigation of superconducting NbN nanowires which were prepared by means of positive-and negative electron-beam lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist. We show that nanowires with a thickness 4.9 nm and widths less than 100 nm demonstrate at 4.2 K higher critical temperature and higher density of critical and retrapping currents when they are prepared by negative lithography. Also the ratio of the experimental critical-current to the depairing critical current is larger for nanowires prepared by negative lithography. We associate the observed enhancement of superconducting properties with the difference in the degree of damage that nanowire edges sustain in the lithographic process. A whole range of advantages which is offered by the negative lithography with positive PMMA resist ensures high potential of this technology for improving performance metrics of superconducting nanowire singe-photon detectors.

References in corpus (4)

• Critical-Current Reduction in Thin Superconducting Wires Due to Current Crowding
• Current dependence of the 'red' boundary of superconducting single photon detectors in the modified hot spot model
• Design of polarization-insensitive superconducting single photon detectors with high-index dielectrics
• Current dependence of the hot-spot response spectrum of superconducting single-photon detectors with different layouts

Cited by in corpus (4)

• Large-area microwire MoSi single-photon detectors at 1550 nm wavelength
• Proximity effect model of ultra-narrow NbN strips
• Superconducting Nanowire Single-Photon Detector (SNSPD) with 3D-Printed Free-Form Microlenses
• Reversible Tuning of Superconductivity in Ion-Gated NbN Ultrathin Films by Self-Encapsulation with a High-$\kappa$ Dielectric Layer