Large surface area IrOx nanofoils (IrOxNF) were deposited on multi-wall carbon nanotube (MWCNT) templates, forming IrOx/MWCNT nanocomposites, by reactive radio frequency magnetron sputtering using Ir metal target. The structural and spectroscopic properties of IrOxNF were characterized. The micrographs of field emission scanning electron microscopy showed the formation of foil-like structure for the as-deposited samples. Transmission electron microscopy analysis revealed the contiguous presence of glassy iridium oxide, iridium metal, and iridium dioxide nanocrystals in the foil. X-ray photoelectron spectroscopy analysis provided the information of the oxidation states and the stoichiometry of IrOxNF. Raman spectra revealed the amorphous-like phase of the as-deposited IrOxNF. The nanofoil structure provided ultra-high surface area for electrical charge storage which made the IrOx/MWCNT nanocomposites as an attractive candidate for the supercapacitor applications. (C) 2011 Elsevier B.V. All rights reserved.