Nucleation-enhancing treatment for diamond growth over a large-area using magnetoactive microwave plasma chemical vapor deposition

A novel pretreatment enhancing diamond nucleation has been developed for diamond growth over a large area using a magnetoactive microwave plasma chemical vapor deposition method. After the predeposition of carbon films on Si(100) substrates using CH4/CO2/He gas mixtures, diamond films with high nucleation densities were obtained after a subsequent 2 h growth process commonly employed using a CH4/CO2/H2 gas mixture. In the present study, especially, the effect of CO2 concentration in the CH4/CO2/He gas mixture in the pretreatment process has been examined on the carbon film growth. The results show that the diamond nucleation with densities as high as ∼109/cm2 was attained for small CO2 concentrations of 1%–2% during the pretreatment process, while no successful enhancement was enabled for Si substrates pretreated at high CO2 concentrations beyond 3.7%. The structural property of the predeposited carbon films significantly influenced the diamond nucleation. This was evidenced by in situ data of optical emi...