  Vortex dynamics is strongly connected with the mechanisms responsible for the
photon detection of superconducting devices. Indeed, the local suppression of
superconductivity by photon absorption may trigger vortex nucleation and motion
effects, which can make the superconducting state unstable. In addition,
scaling down the thickness of the superconducting films and/or the width of the
bridge geometry can strongly influence the transport properties of
superconducting films, e.g. affecting its critical current as well as its
switching current into the normal state. Understanding such instability can
boost the performances of those superconducting devices based on nanowire
geometries. We present an experimental study on the resistive switching in NbN
and NbTiN ultra-thin films with a thickness of few nanometers. Despite both
films were patterned with the same microbridge geometry, the two
superconducting materials show different behaviors at very low applied magnetic
fields. A comparison with other low temperature superconducting materials
outlines the influence of geometry effects on the superconducting transport
properties of these materials particularly useful for devices applications.

Superconductivity