New surface features on high-pressure high-temperature diamond octahedrons observed by confocal laser scanning microscope

Trigons on the surface of diamonds are correlated with defects in their crystal lattices. However, due to the rarity of HPHT diamond octahedrons. Few studies have focused on surface features of them. Here, we made detailed observation and description of as-grown surface features on 27 HPHT diamond octahedrons produced from China, and reported new features of jagged steps of trigons, 90 degrees oriented trigons, and residual hillocks on diamonds. The formation of these features was discussed, and the relationships between parameters of trigons and hillocks were thoroughly investigated. It was found that the depth of trigons on these HPHT diamond octahedrons was smaller than 1 mu m, and most positive f/b trigons showed the depth limit of 0.2 mu m. Besides, correlations between the diameter, depth, and inclination angle of trigons demonstrated that the development of trigons displayed distinctive characteristics in different stages: In the beginning, when the trigons were relatively small (diameter < 5 mu m), the increasing rate of depth was larger than that of diameter, while when the trigons enlarged to some extent (diameter > 20 mu m), their diameter would develop faster than their depth in the following process. This study expanded our cognition of surface features on diamond, provided solid systematic data for trigons on HPHT diamond octahedrons, and furthered comprehension of the formation process of trigons on the surface of diamonds, which has reference significance for evaluating and improving the quality of synthetic diamond crystals.