Synthesis and tribological characteristics of nanocrystalline diamond film using CH4/H2 microwave plasmas

Abstract

Nanocrystalline diamond film was synthesized on a silicon substrate using CH4/H2 microwave plasmas. The synthesis was carried out for 20 h at 640–680 °C in 10% CH4–H2 gas mixtures at 32 mbar using a coaxial antenna-type microwave plasma chemical vapor deposition (MWPCVD). From the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, the obtained film was found to grow directly as continuous and/or rectangular grains of approximately 5–15 nm from the substrate. The full width at half maximum (FWHM) of the film at 43.9° (2θ) was also approximately 0.35° from the X-ray diffraction (XRD) analysis. In the UV Raman spectrum, the somewhat sharp peak of sp3-bonded carbon attributed to diamond at approximately 1333 cm–1 and broad peak of sp2-bonded carbon attributed to graphite at 1580 cm−1 were observed. The friction coefficient, which was measured with a SiC ball of 6.35 mm diameter with 0.5 N load, was estimated to be approximately 0.05–0.07 in dry air. The hardness measured with a nanoindenter was in the range of approximately 97–104 GPa.