A thin film deposition technique is described whereby the oxidation condition of as-deposited iridium oxide thin films can be manipulated by varying deposition conditions. Iridium oxide thin films were deposited by reactive rf magnetron sputtering in a H2/O2/Ar gas blend. Optical emission spectroscopy, an in-situ process monitor, was employed to observe redox interactions in the deposition plasma. The plasma spectra exhibited characteristics normally observed in hydrogen flame spectroscopy. A competitive redox balance was found to exist between atomic O and atomic H emissions. Plasma redox conditions defined by the H-O emissions could be accessed by a variety of gas flow conditions. Electrochemical aspects of the IrOx films were examined by cyclic voltammetry. Electrochromic capabilities were demonstrated through optical transmittance.