  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.
