Atomic force microscopy and Kelvin probe experiments are applied to characterize hydrogen terminated patterns contacted with gold and aluminum on (100) diamond surfaces. On hydrogen terminated diamond the work function of 4.9 eV is detected, with an accuracy of about 0.1 eV. Taking into account the negative electron affinity of −1.3 eV and a band gap of 5.5 eV the Fermi energy is 0.7 eV deep in the valence band. Illumination of the sample results in a shift of the surface Fermi level by as much as 0.2 eV. This is attributed to a surface photovoltage effect.

Three hydrogen-terminated diamonds with different surface roughness and morphologies have been investigated by conductivity and Hall experiments in the temperature regime 0.34–350 K. The sheet hole densities are weakly temperature dependent above a critical temperature Tc (20 K⩽Tc⩽70 K), below Tc carriers freeze out. The mobilities of holes show a minimum at Tc increasing towards higher and even stronger towards lower temperatures significantly up to 400 cm2/V s. A transport model is introduced where holes propagate in the valence band where a disorder-induced tail of localized states is present.

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