In this study, the effects of an (NH4)(2)S-x treatment on the surface work function (SWF) and roughness of indium-tin-oxide (ITO) have been investigated. From the observed X-ray photoelectron spectroscopy results, optical transmittance measurements, atomic force microscopy measurements and four-point probe measurements, it is suggested that the surface chemical changes and an increase in the sheet resistance had strong effects on the SWF of ITO. We find that the S occupation of oxygen vacancies near the ITO surface after (NH4)(2)S-x treatment may result in a marked increase in the SWF and a slight increase in the surface roughness. (c) 2006 Elsevier B.V. All rights reserved.