Synthesis of nanocrystalline diamond embedded diamond-like carbon films on untreated glass substrates at low temperature using (C2H2 + H2) gas composition in microwave plasma CVD

Diamond-like carbon (DLC) films with well distinguished nanocrystalline diamond (NCD) grains embedded in the matrix are grown at-300 ?C on glass substrates without any pre-treatment, using a specially-designed stainless-steel shadow-mask assembly creating diffuse secondary plasma that shields the growth zone from high energy ion bombardment. The effects of different compositions of the precursor gas, R = C2H2 / (C2H2 + H-2), and gas pressure in the plasma at 500 W of microwave power demonstrate their significant influences on controlling the relative composition of the sp(3) to sp(2) hybridized carbon phases in the films. The maximum intensity ratio of I-Dia/I-G (-1.05) and I-Dia/I-D (-1.05) along with the corresponding minimum of I-D/I-G (-1.0) appearing in the Raman spectrum at R = 0.33 and 25 Torr pressure, correlate a superior diamond-phase containing-55% sp(3)-hybridized carbon in the DLC network having high optical transmittance of-87% at 600 nm wavelength. A homogeneous microstructure with uniform distribution of the NCD grains of average size-10 nm and <1 1 1> crystallographic orientation, and smooth surface morphology with average roughness-2.1 nm is obtained in the optimum NCD embedded DLC film, the growth mechanism of which is discussed on the basis of parametric changes.