We report on the synthesis and functional properties of nanoscale (similar to 50 nm) dense Y-doped zirconia (YDZ) electrolyte thin films by photon-assisted oxidation of Zr-Y precursor alloy thin films. Crystalline zirconia films with grain size of similar to 5 nm were successfully grown at room temperature by oxidation under ultra-violet (UV) photon irradiation. Microstructure of the films was characterized by transmission electron microscopy. The electrochemical conductivity of UV grown YDZ electrolytes was investigated over a broad range of temperatures using Pt electrodes as a function of yttria doping concentration. The slightly lower electrical conductivity in UV grown films at intermediate temperature range (400-550 degrees C) is consistent with previous reports on oxygen defect annihilation under photo-excitation. Micro-fuel cells utilizing such ultra-thin YDZ membranes yielded similar to 12 mW cm(-2) power density at 550 degrees C. The results are of potential relevance in advancing low temperature ultra-thin oxide membrane synthesis for energy applications. (C) 2009 Elsevier B.V. All rights reserved.