High-Pressure, High-Temperature Heteroepitaxial Growth of Large Single-Crystal Diamonds

Heteroepitaxial diamond growth using the chemical vapor deposition method is a successful approach to overcoming the size limitation of homoepitaxial substrates. However, the dislocation density in the resulting crystals remains high. In contrast, the High-Pressure High-Temperature method enables the growth of diamonds with low dislocation density, but its application in the synthesis of heteroepitaxial large single-crystal diamonds has yet to be explored. Here, the first growth of large diamonds on cubic boron nitride (cBN) and silicon carbide (SiC) seeds is reported using the temperature gradient method at 5.5 GPa and different temperatures. The results show that diamonds grown on cBN exhibited a high content of isolated nitrogen atoms (C-center) and the lowest quality. The dislocation density of diamond grown on SiC seeds, as observed by selective etching, is only ≈2.5 × 10⁴ cm^-2, the lowest value reported so far. A novel misfit accommodation mechanism revealed that during the early growth stages, the axial interplanar spacing increased. An amorphous-diamond mixed buffer zone of at least 40 nm mitigated lattice mismatch, and as synthesis progressed, the dislocation density decreased, improving the crystal quality. Heteroepitaxial diamond can also achieve the crystal quality of homoepitaxial diamond.