An investigation of a thin metal film covering on HPHT as-grown diamond from Fe–Ni–C system

Scanning Raman spectroscopy, scanning auger microprobe, electron probe microanalysis, X-ray powder diffraction and transmission electron microscopy were used to investigate a thin metal film covering on HPHT as-grown diamond from Fe–Ni–C system. In different regions of the film, the fine structure of carbon and iron atoms are different. It is clear that the microstructure and composition in the inner part of the film near diamond are different from those in other regions of the film. The fine structures of carbon and iron atoms have been greatly transformed. Crystalline graphite and amorphous carbon were not found in the inner part near diamond. The diamond formation should be directly associated with carbide. There exist parallel relationships between the crystal faces of (Fe,Ni) and Fe3C. We suggest that graphite could not be directly catalyzed into diamond structure in the molten film, and the carbon for diamond growth may be related to the decomposition of Fe3C under the effect of (Fe,Ni) phases in the inner part, which can play an important role under diamond growth at high temperature and high pressure.