Electronic properties of plasma hydrogenated diamond surfaces: A microscopic study

The quality of hydrogen termination of undoped diamond surfaces is investigated on a microscopic level by applying atomic force microscopy, Kelvin force microscopy, and scanning electron microscopy. The results show that high temperature hydrogenation in a microwave plasma can lead to microscopic inhomogeneities at the surface, both in morphology and electron emission properties. These inhomogeneities are due to a very thin (1 nm) layer of non-diamond material on the surface, which appears to be inherently generated by the hydrogen plasma process. By scanning in contact AFM an underlying diamond surface can be exposed, which retains properties typical for hydrogenated diamond and exhibits significantly improved electron emission properties.