A contactless surface photovoltage technique was used to measure surface-potential barriers resulting from hydrogen termination of silicon surfaces and their evolution as the surfaces gradually oxidized in air at room temperature. Hydrogen termination formed by annealing in a hydrogen ambient was more complete than passivation formed by aqueous I-IF treatment. Eu addition, the surface-potential barrier depended on the wafer orientation and ordering of surface terraces by high temperature hydrogen annealing. Oxides grown at room temperature exhibited higher surface-potential barriers than oxides grown at elevated temperatures.