Optical and mass spectroscopy measurements of Ar/CH4/H2 microwave plasma for nano-crystalline diamond film deposition

Nano-crystalline diamond (NCD) thin film with grains of about 5–100 nm in size attracts much attention as new functional materials in various industrial fields, due to its unique properties that are different from the conventional microcrystalline diamond (MCD) thin film. Most commonly, NCD film can be synthesized using CH4/Ar plasma with/without a small amount of hydrogen gas added. In this study, we carried out the measurements of quadrupole mass spectroscopy (QMS) and optical emission spectroscopy (OES) to investigate CH4/H2/Ar mixture plasma in detail. Combined with our experimental results of NCD film synthesis, the mechanism of CH4 dissociation and the precursors of NCD were further explored.