It is shown that amorphous Nb2O5films 2400 Å thick produced by anodization can be doped with Nb by rf sputtering of Nb atoms at substrate temperatures of 150°C. Large increases in electrical conductivity, reductions in thermal activation energy, and increases in capacitance as function of sputtering voltage in the range 2−5 kV support this interpretation. The high−field conduction process also changes from the Poole−Frankel mechanism often found in insulating films, where the conductanceG=G0exp(KV1/2) to the Poole mechanism whereG=G0exp(KV) found in Nb doped films. The doping concentration for 2400−Å films was calculated using the experimental values of the exponentKand found to be 1019atoms/cm3for films sputtered with Nb at an rf voltage of 3 kV. Capacitance variation as a function of voltage and temperature also support these conclusions. These effects are interpreted on the basis of possible implantation and temperature−aided diffusion process.