Characterization of diamond-like carbon thin films prepared by a microwave plasma enhanced chemical vapor deposition method

Diamond-like carbon thin films were prepared by the microwave plasma-enhanced chemical vapor deposition method on silicon substrates using a methane (CH4) and hydrogen (H2) gas mixture. The negative DC bias (450∼550 V) was applied to enhance the adhesion between the film and the substrate. The Raman spectroscopy shows the DLC amorphous structure of the films. AFM images show that the surface roughness of the DLC film decreases with increasing the negative DC bias voltage. The hardness and Youngʹs modulus were measured with a nano-indentor and it showed that the Youngʹs modulus decreases as the substrate DC bias voltage increases and also, the friction coefficient was investigated by atomic force microscopy (AFM) in friction force microscope (FFM) mode, which was compared with data by the pin-on disk (POD) measurement. FFM and POD results show that we can obtain good DLC thin films at higher substrate DC bias voltage without any additional dopant from the tribological point of view.