HPHT synthesis and crystalline quality of large high-quality (001) and (111) diamond crystals

• High-quality type IIa diamond crystals up to 12 mm in diameter are grown under HPHT.
• The (001) and (111) diamonds are grown on (001)-oriented and (111)-oriented seeds.
• The both large crystals have very few crystal defects in the {100} growth sectors.
• The rocking curves in the {100} growth sectors are close to the theoretical curve.

High-quality type IIa diamond crystals measuring up to 12 mm in diameter (8 to 10 carats) were successfully grown by the temperature gradient method at high pressure and high temperature (HPHT) on defect-free (001)-oriented and (111)-oriented seed crystals. The crystalline quality of the grown crystals was qualitatively evaluated by synchrotron based X-ray topograph and rocking curve (RC) measurements. The results revealed that the crystals grown on (001)-oriented seeds have extremely high quality in the (001) growth sector, which extends straight upward from the seed surface. This sector contains very few dislocations and stacking faults in the upper part in particular, where the RC almost agrees with the theoretical curve. For the crystals grown on (111)-oriented seeds, it was confirmed that crystal defects are fewer in the outer (100), (010), and (001) growth sectors than in the central (111) growth sector extending straight upward from the seed surface. The RCs in selected regions of these {100} growth sectors are close to the theoretical curve, indicating high crystalline quality.

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