Tuning the resistive switching of superconducting films by geometry effects

In a superconducting photon detector, the effective transition to the normal state can be induced by the instability of the flux flow regime. Indeed, in the presence of self-magnetic field, the local suppression of superconductivity induced by photon absorption determines vortex nucleation and flux flow regime, which can make the superconducting state unstable. Understanding such instability can boost the performances of those superconducting devices based on this resistive switching. Here, we present the study of the geometry influence on such instability in NbN and NbTiN ultrathin films. Despite the same patterned microbridge geometry, the two superconductors show different behaviors at very low applied magnetic fields. A comparison with other superconductors outlines the possibility to tune the resistive switching by geometry effects in interesting materials for devices applications. Finally, we also report the influence of the cooling environment on the electric critical power in superconducting thin films.