Research of microstructural characteristics on nanocrystalline diamond by microwave plasma CVD

► A less amount of H2 content additive has improved the aggregation of the nucleation film to form the NCD films. ► The average grain sizes of the diamond film increases as the H2 concentration increased. ► The microstructure of diamond films were transited from microcrystalline structure to nanocrystalline structure as the concentration of H2 decreases. ► The NCD film possessed a highly hydrophobic property.