AbstractPhotovoltaic effects in ultraviolet photoemission spectroscopy of the in-situ “rehydrogenated”, and reconstructed (111) diamond surfaces are evaluated. We show that photovoltaic charging effects during photoemission studies of the in-situ “re-hydrogenated” (111)-(l×l):H diamond surface are significant at temperatures as high as room temperature. In contrast, experiments on the reconstructed (111 )-(2×l) diamond surface find no photovoltaic charging which suggests that the surface exhibits relatively high conductivity (effectively grounded surface). These results demonstrate that extra care should be taken in determining the Fermi level pinning position relative to the bands at diamond surfaces and interfaces. The assumption that the UPS photoelectron spectra reflect the equilibrium energy band arrangement should be experimentally confirmed in each case, especially when wide band gap materials are involved.