Tantalum oxide films were deposited by pulsed and continuous wave (CW) plasma-enhanced chemical vapor deposition (PECVD). The pulsed films were stoichiometric and free of impurities as measured by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. CW films contained significant amounts of hydroxyl impurities, resulting in a nonstoichiometric composition with an O/Ta ratio of similar to 2.8. Impedance spectroscopy was used to quantify ion transport through electrochromic half-cells formed by depositing tantalum oxide on both tungsten and vanadium oxides. Logarithmic plots of the imaginary component of impedance vs frequency were employed to extract equivalent circuit parameters. Despite the differences in composition the pulsed and CW films displayed similar ionic conductivities, with values of similar to 6x10(-10) and similar to 2x10(-10) S/cm for H+ and Li+, respectively. However, the pulsed PECVD films displayed dramatically reduced electrical leakage. The ratio of ion/electron conductivity exceeded 100 for pulsed PECVD films, while sigma(ion)/sigma(e) was < 1 in CW material. (C) 2008 The Electrochemical Society.