Characterization of a growth-front interface in a HPHT-grown diamond crystal by transmission electron microscopy

The growth-front interface of a diamond single crystal, which was grown fro m the Fe - Ni - C system under high pressure and high temperature (HPHT), h as been directly observed by transmission electron microscopy (TEM) for the first time. The presence of a cellular interface suggests that the diamond is grown from solution and there exists a narrow supercooling zone in fron t of the solid-liquid interface. Diamond-growth parallel layers were also f ound, which indicates that the diamond grows from solution layer by layer. It provides direct evidence that the diamond is synthesized through graphit e dissolution and transformation to subcritical diamond particles in a molt en catalyst, diamond subcritical particle connection to form diamond cluste rs, diffusion of the diamond clusters to the growing diamond, and unificati on of the diamond clusters on the growing diamond crystal.