High-Rate Growth and Nitrogen Distribution in Homoepitaxial Chemical Vapour Deposited Single-crystal Diamond

High rate (> 50 μm/h) growth of homoepitaxial single-crystal diamond (SCD) is carried out by microwave plasma chemical vapour deposition (MPCVD) with added nitrogen in the reactant gases of methane and hydrogen, using a polycrystalline-CVD-diamond-film-made seed holder. Photoluminescence results indicate that the nitrogen concentration is spatially inhomogeneous in a large scale, either on the top surface or in the bulk of those as-grown SCDs. The presence of N-distribution is attributed to the facts: (i) a difference in N-incorporation efficiency and (ii) N-diffusion, resulting from the local growth temperatures changed during the high-rate deposition process. In addition, the formed nitrogen-vacancy centres play a crucial role in N-diffusion through the growing crystal. Based on the N-distribution observed in the as-grown crystals, we propose a simple method to distinguish natural diamonds and man-made CVD SCDs. Finally, the disappearance of void defect on the top surface of SCDs is discussed to be related to a filling-in mechanism.