Surface terminations of diamond play an important role in determining the electric properties of diamond-based electronic devices.We report an ultraviolet/ozone (UV/ozone) treatment process on hydrogen-terminated single crystal diamond (H-diamond) to modulate the carrier behavior related to varying oxygen adsorption on surfaces.By UV/ozone treatments,the induced oxygen radicals are chemically adsorbed on the H-terminated diamond and replace the original adsorbed H,which is analyzed by x-ray photoelectron spectroscopy.The concentration of oxygen adsorbed on surface increases from ～3％ to ～8％ with increasing the ozone treatment time from 20s to 600s.It is further confirmed by examining the wettability properties of the varying diamond surfaces,where the hydrophobic for H-termination transfers to hydrophilic for partly O-termination.Hall effect measurements show that the resistance (hole mobility) of the UV/ozone-treated H-diamond continuously increases (decrease)by two orders of magnitude with increasing UV/ozone treatment time from 20s to 600s.The results reveal that UV/ozone treatment becomes an efficient method to modulate the surface electrical properties of H-diamonds for further investigating the oxygenation effect on two-dimensional hole gas based diamond devices applied in some extreme environments.