Atomic and microstructural characterization of metal impurities in synthetic diamonds

The phase and microstructure of Ni, Co, and Fe impurities found in synthetic diamonds have been characterized in some detail using a combination of extended x-ray absorption fine structure (EXAFS) utilizing intense synchrotron radiation as a light source, and conventional transmission electron microscopy (TEM), x-ray diffraction, and fluorescence analyses. In all three cases, the metal impurity exists as an fcc metallic phase dispersed in the diamond matrix. The particles are submicron in size and not facetted. There was no evidence of a metal carbide phase in these systems. Quantitative simulations of the first-shell EXAFS signal showed that the Co and Ni particles contain, respectively, 2.3 and 1.5 at. % of carbon in solution.