Effect of Metallic Film in Diamond Growth from an Fe-Ni-CSystem at High Temperature and High Pressure

Abstract

The metallic film surrounding a diamond single crystal, whichplays an important role in the diamond growth from an Fe-Ni-C system,has been successfully investigated by using transmission-electron microscopy (TEM), Raman spectroscopy and x-ray photo-electronspectroscopy (XPS). Diamond and graphite were not found in surfacelayer (near diamond) of the film by TEM and Raman spectroscopy, but aparallel relationship exists between the (11̄1̄) plane ofγ-(Fe,Ni) and the (100) plane of (Fe,Ni)3C in this region.Compared with that of solvent metal (catalyst) near diamond, the bindingenergy in the valence bands of iron, nickel and carbon atoms of thefilm has an increase of 0.9 eV. According to the microstructures on thefilm obtained by the TEM, Raman spectra, and XPS, the catalyticmechanism of the film may be assumed as follows. In the surface layerof the film, iron and nickel atoms in the γ-(Fe,Ni) lattice can absorbcarbon atoms in the (Fe,Ni)3C lattice and make themtransform to an sp3-like state. Then carbon atoms withthe sp3-like structure are separated from the (Fe,Ni)3C andstack on the growing diamond crystal. This study provides a directevidence for the diamond growth from a metallic catalyst-graphite systemunder high temperature and high pressure.