LAUSR

Abstract Diamond nucleation on iron and iron alloy substrates is comparatively investigated by high resolution transmission electron microscopy (HRTEM). A unique interfacial microstructure is observed between diamond film and iron substrate. Besides a graphite interlayer formed on the substrate surface, many unique clusters are observed to distribute randomly in the transitional zone from the graphite interlayer to the continuous diamond film. These clusters present a complex structure containing polycrystalline diamond, amorphous carbon, iron carbide particles and graphite, which are all closely associated with the nucleation sites for the diamond phase. The findings reveal that diamond is unlikely to directly nucleate and grow on a pure graphite interlayer. Meanwhile, diamond nucleation nanoparticles are observed at the surfacial grooves through the study of the very early stage of diamond nucleated on iron alloy substrate. These diamond nuclei are elongated about 10–15 nm (about 5 nm in width) and surrounded by the amorphous carbon, suggesting the mechanism that the diamond nucleates spontaneously from the amorphous carbon.