We report on the chemical adsorption of acids and bases on indium tin oxide (ITO). Ultraviolet photoelectron spectroscopy was used to measure the work function of the treated ITO and atomic surface concentrations were determined by x-ray photoelectron spectroscopy. The acid treatments yield work-function shifts as high as 0.7 eV compared to the nontreated ITO. Huge shifts in the work function are also obtained for the treatments with bases and are opposite to those obtained with the acids. These dramatic shifts are indicative of a double ionic surface layer. The importance of an appropriate plasma treatment prior to the chemical adsorption of acids or bases is discussed in terms of surface acido-basicity.
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