Local Structure of Nanocrystalline Diamond - Evolution with Thermal Treatments

High intrinsic hydrogen concentrations (up to 10 cm for nanocrystalline diamond) are found in diamond grown by microwave plasma chemical vapour deposition (MP CVD) or by hot filament chemical vapour deposition. The sp/sp carbon bonds ratio in nanocrystalline diamond thin films deposited by chemical vapour deposition may reach 10%. Hydrogen concentration has been related to grain size and sp carbon phase concentration in previous works [1]. The presence of disordered hydrogenated sp carbon in grain boundaries, a high density of dislocations which may trap hydrogen, together with the presence of H2 dimers, are supposed to explain this high hydrogen concentration [2].