1D superconductivity in porous Nb ultrathin films

We report on the measurements of the transport properties of superconducting Nb ultrathin bridges grown by UHV magnetron sputtering on porous Si substrates. The films are about 10 nm thick and inherit from the substrate a structure made of holes with diameter of 10 nm and interpore spacing in the range 20-40 nm. Due to their reduced dimensions, they are sensitive to thermal fluctuations typical of 1D superconductors and exhibit a nonzero resistance below the superconducting transition temperature, Tc. Clear hysteresis and finite jumps in the I-V curves are also observed.