Crystalline quality distributions of the type IIa diamond substrate and the CVD diamond layer processed by chemical mechanical polishing using a SiO2 wheel

We have grown a high-quality type-IIa single-crystal diamond substrate, which had a large (001) growth sector with a dislocation-free area of 3.5 × 3.5 mm2, and strong free exciton (FE) emissions were observed by cathodoluminescence (CL), while dislocations, stacking faults, and defect-related CL emissions at 340 and 400 nm were observed in the (111) growth sector. After CVD growth on the off-angled type-IIa substrate processed by SiO2 chemical mechanical polishing, the intensity of the FE emission became 3 times higher and the electronic quality became more homogeneous, indicating that a high-quality CVD layer was successfully grown and the lateral growth eliminated the evolution of point defects in the substrate. On the other hand, the CVD layer on the (111) growth sector had hillocks and defect-related CL emissions, indicating that the stacking faults have a highly negative effect on the electronic quality of the CVD layer compared with the dislocations.