Effects of surface modification on the electrical conductivity of proton conducting oxides (Yttrium doped BaCeO3), irradiated by 10 keV Ar+ ions to a fluence of 1.0 x 10(18) ions/cm(2) in room temperature, were investigated by means of ultraviolet-visible (UV-VIS) optical absorption, X-ray photoelectron spectroscopy (XPS), elastic recoil detection analysis (ERDA) and alternating current (AC) impedance measurements. UV-VIS and XPS analyses showed that oxygen vacancies and hydroxides formed on the irradiated specimen and that proton concentration increased on the surface by the ERDA. The electrical conductivity of the modified specimen became about one order of magnitude higher in the temperature range of 298-673 K. These results indicate that the increase of electrical conductivity may be caused by the increase of proton and electronic carriers formed by the interaction of oxygen vacancies and H2O or O-2, respectively. (c) 2008 Elsevier B.V. All rights reserved.