Mechanisms of surface conductivity in thin film diamond: Application to high performance devices

It has been known for some time that hydrogen within the bulk of diamond increases the conductivity of the material. However, only recently did it become apparent that the surface of thin film diamond can display p-type conductivity and that this too related to the presence of hydrogen. The origin of this effect has been controversial. We have used a wide range of techniques to study hydrogenated polycrystalline CVD diamond films to solve this problem. The generation of near surface carriers by hydrogen, which resides within the top 20 nm of `as-grown' CVD films, is the origin of the conductivity rather than surface band bending which had also been proposed. Up to 1019 holes cm-3 can be measured and mobilities as high as 70 cm2/Vs recorded. H-termination of the surface is important for the formation of high quality metal-diamond interfaces