Characteristics of nano-crystalline diamond films prepared in Ar/H2/CH4 microwave plasma

Characteristics of nano-crystalline diamond (NCD) thin films prepared with microwave plasma chemical vapor deposition (CVD) were studied in Ar/H2/CH4 gas mixture with a CH4 gas ratio of 1–10% and H2 gas ratio of 0–15%. From the Raman measurements, a pair of peaks at 1140 cm− 1 and 1473 cm− 1 related to the trans-polyacetylene components peculiar to nano-crystalline diamond films was clearly observed when the H2 gas ratio of 5% was added in Ar/H2/CH4 mixture. With an increase of H2 gas content up to 15%, their peaks decreased, while a G-peak at roughly 1556 cm− 1 significantly increased. The degradation of NCD film quality strongly correlates with the decrease of C2 optical emission intensity with the increase of hydrogen gas contents. From the surface analysis with atomic force microscopy (AFM), it was found that grain sizes of NCD films were typically of 10–100 nm in case of 5% H2 gas addition.