Origin of surface conductivity in diamond

Hydrogen-terminated diamond exhibits a high surface conductivity (SC) that is commonly attributed to the direct action of hydrogen-related accepters. We give experimental evidence that hydrogen is only a necessary requirement for SC; exposure to air is also essential. We propose a mechanism in which a redox reaction in an adsorbed water layer provides the electron sink for the subsurface hole accumulation layer. The model explains the experimenta l findings including the fact that hydrogenated diamond is unique among all semiconductors in this respect.