Enhanced nucleation behavior for ultra-nanocrystalline diamond on Si-substrates via the utilization of Mo-coating was observed. Spectroscopic examinations indicated that the mechanism of enhancement is the formation of Mo2C phase, which hindered the inward diffusion of carbon species into the substrate materials. The diamonds may either nucleate directly on Mo2C-layer or via the formation of transition phases, the graphite. The incoming carbons may also react with Mo2C phase to form MoC phase or form the graphite phase prior to the induction of diamond nuclei. In all cases, the carbons accumulated rapidly due the presence of a Mo2C (or MoC) layer, triggering the formation of diamond nuclei.
