Influence of thickness, width and temperature on critical current density of Nb thin film structures

The density of critical currents jC in Nb thin films with thickness smaller than 15 nm and width between 100 nm and 10 μm has been measured in a wide temperature range. We have found that the temperature dependencies of jC in sub-micrometer wide bridges at 0.7TC < T < TC are well described by the Ginzburg-Landau de-pairing critical current. In wider bridges already at T < 0.9TC the jC value is significantly reduced due to the penetration and de-pinning of magnetic vortices.