The effect of additional methane during the annealing process on diamond nucleation on polished polycrystalline nickel substrates

The density and quality of diamond nuclei on nickel substrates are greatly enhanced by additional CH4 in the high-temperature annealing process. If we increase the concentration of CH4 from 0.5 to 2.5% in this process, the quality of diamond nuclei will be improved, in which the 1.5% CH4 concentration is found to be the best fit for diamond to nucleate on nickel substrates. During the annealing step with the 1.5% CH4 concentration, the density of diamond nuclei is up to 3×108/cm2, higher than the density of nuclei on nickel substrates in previous works and the quality of diamond is nice.