Upper critical field and fluctuation conductivity in Nb-doped strontium titanate thin films

We show that the transition temperature T-c of Nb-doped strontium titanate thin films grown in vacuum by pulsed laser deposition is similar to bulk and that these films follow a similar dependence of T-c on the carrier density as bulk. We have measured the temperature dependence of the upper critical field H-c2 in thin films. We tit the data to the empirical temperature dependence H(c2)infinity(1-t(2))/(1 + t(2)), where t= T/T-c, and determined the electronic diffusion constant from the slope of dH(c2)/dT near T-c. We further fit the temperature dependence of thr fluctuation conductivity above T-c successfully to the theories of Aslamazov-Larkin and Maki-Thompson.