High-resolution spatial mapping of a superconducting NbN wire using single-electron detection

TL;DR

This paper demonstrates high-resolution spatial mapping of a superconducting NbN wire's detection efficiency for single electrons using a scanning electron microscope, revealing inhomogeneities at the nanoscale.

Contribution

It introduces a novel method for characterizing superconducting nanowires with sub-150 nm resolution using electron detection.

Findings

Detection efficiency map shows inhomogeneities at 150 nm scale

Method achieves superior resolution compared to optical techniques

Enables detailed characterization of superconducting wire properties

Abstract

Superconducting NbN wires have recently received attention as detectors for visible and infrared photons. We present experiments in which we use a NbN wire for high-efficiency (40 %) detection of single electrons with keV energy. We use the beam of a scanning electron microscope as a focussed, stable, and calibrated electron source. Scanning the beam over the surface of the wire provides a map of the detection efficiency. This map shows features as small as 150 nm, revealing wire inhomogeneities. The intrinsic resolution of this mapping method, superior to optical methods, provides the basis of a characterization tool relevant for photon detectors.