This study examined the effects of H-2 and H-2 + O-2 mixed gas plasma treatment on the properties of ITO films. The films were deposited on corning glass by RF magnetron sputtering under Ar and Ar/O-2 mixed gas ambient. After a H-2 plasma treatment, the ITO films showed an improved specific resistance due to the formation of oxygen vacancies acting as shallow donors, but showed quenched transmittance due to the formation of agglomerated metals on the surface. After an H-2 + O-2 mixed gas plasma treatment, the specific resistance of the film was improved without deteriorating transmittance. The enhanced specific resistance by mixed gas plasma treatment was attributed to the formation of free electrons by the incorporation of H in the lattice. (C) 2012 Elsevier B.V. All rights reserved.