Light Induced Electron-Phonon Scattering Mediated Resistive Switching in Nanostructured Nb Thin Film Superconductor

TL;DR

This study reveals that nanostructured Nb thin films exhibit room temperature photo-switching and bolometric effects under light, with potential applications in superconducting photon detectors and bolometers, driven by photon-assisted electron-phonon scattering.

Contribution

It introduces the novel optoelectronic properties of nanostructured Nb thin films, demonstrating their resistive switching and bolometric behavior under optical illumination, which was previously unexplored.

Findings

Nanostructured Nb films act as room temperature photo-switches.

Light shifts superconducting transition to lower temperature.

Resistivity changes depend on film thickness and grain size.

Abstract

The elemental Nb is mainly investigated for its eminent superconducting properties. In contrary, we report of a relatively unexplored property, namely, its superior optoelectronic property in reduced dimension. We demonstrate here that nanostructured Nb thin films (NNFs), under optical illumination, behave as room temperature photo-switches and exhibit bolometric features below its superconducting critical temperature. Both photo-switch and superconducting bolometric behavior are monitored by its resistance change with light in visible and near infrared (NIR) wavelength range. Unlike the conventional photodetectors, the NNF devices switch to higher resistive states with light and the corresponding resistivity change is studied with thickness and grain size variations. At low temperature in its superconducting state, the light exposure shifts the superconducting transition towards lower temperature. The room temperature photon sensing nature of the NNF is explained by the photon assisted electron-phonon scattering mechanism while the low temperature light response is mainly related to the heat generation which essentially changes the effective temperature for the device and the device is capable of sensing a temperature difference of few tens of milli-kelvins. The observed photo-response on the transport properties of NNFs can be very important for future superconducting photon detectors, bolometers and phase slip based device applications.