High-pressure preparation of high-roughness diamond single crystals and analysis of surface morphology

Abstract

In this work, diamond single crystals with high surface roughness were prepared in an FeNi solvent under a pressure of 5.4 GPa. The impact of the dissolution time, temperature, and oxygen concentration in the environment on the morphology, surface shape, surface roughness, and crystalline quality of the diamond was systematically explored. Our analysis showed that, with the extension of dissolution time (2 h–18 h), the distribution of pyramidal hillocks on the {100} plane of the crystal changed from sparse to dense, and the surface roughness increased from 0.06 μm to 7.22 μm. With increases in the dissolution temperature (1200 ℃–1420 ℃), the dissolution rate of the crystal became significantly elevated, and the surface roughness decreased from 7.22 μm to 1.84 μm. Furthermore, Ni2O3 was added to FeNi to change the oxygen concentration in the dissolution environment. The addition of oxygen reduces the roughness of the entire crystal, but makes the distribution of the defect shapes (triangles and quadrilaterals) on the crystal surface more regular and dense. In addition, the light transmittance of diamond after the implementation of the HPHT surface treatment was enhanced and the half-maximum width was narrowed. These results indicate that through the synergistic control of dissolution time, dissolution temperature, and dissolution environment, high-roughness diamond single crystals can be fabricated, and their surface morphology can be controllably engineered.