Investigation of Diamond/Metallic Film Interface and Valence Electron Structure Analysis of Diamond Growth

The diamond/metallic film interface has been studied using transmission electron microscopy and electron backscatter diffraction. This interface is significant in the graphite/diamond transition procedure, where a metallic film from the Fe–Ni–C system covers the diamond during its growth at high pressure and high temperature. It is reveals that the metallic film interface consists of γ-(Fe,Ni) and orthorhombic Fe₃C, with γ-(Fe,Ni) present in tetragonal shapes whose exposed surfaces are likely to be (001) crystal surfaces. Furthermore, the valence electron structures of Fe₃C, γ-(Fe,Ni), and diamond were calculated, and the relative electron density differences of diamond growth interfaces were analyzed using the empirical electron theory of solid and molecules. It is found that the relative electron density differences of Fe₃C/diamond interfaces are continuous at the first order of approximation, indicating that the carbon atoms decomposing from Fe₃C can be transformed into diamond structure. Additionally, the relative electron density differences of γ-(Fe,Ni)/Fe₃C interfaces were found to be continuous. Therefore, it is suggested that carbon atoms for diamond growth may come from the decomposition of Fe₃C, while γ-(Fe,Ni) serves as a catalytic phase to promote the decomposition of Fe₃C.