Structural and mechanical characterization of diamond like carbon films grown by microwave plasma CVD

Diamond like carbon (DLC) films is useful for tribology, optical and biocompatible coating applications. Plasma-activated processes such as radio frequency (RF) plasma CVD and electron cyclotron resonance (ECR) microwave (MW) plasma CVD are usually used to grow DLC films. By using a bowl shaped steel substrate holder in a 3 kW MW plasma CVD reactor (without ECR), DLC films have been grown at relatively high pressure using CH4, H2 and Ar gas mixture. Raman spectra of the grown films show typical G (1580 cm−1) and D (1350 cm−1) bands and transmission electron microscopy (TEM) image show nanocrystalline structure, further, FTIR and UV–visible spectra show presence of hydrogenated sp3 polymeric carbon and high visible transmittance (∼ 85%) of the films. These films show reasonable mechanical properties (hardness around 6–16 GPa and Young's modulus 160–200 GPa) and have smooth surface morphologies as revealed by atomic force microscope (AFM) having rms roughness value about 3 nm. These films show polymeric DLC characteristics, which may be useful as anti-corrosion and scratch-resistant coatings.