Diamond-like carbon films deposited on polymers by plasma-enhanced chemical vapor deposition

Diamond-like carbon (DLC) films were deposited on polycarbonate (PC) by r.f. plasma-enhanced chemical vapor deposition. Methane (CH4) and diluted hydrogen (H2) were used for film deposition. Influences of CH4 content in CH4/H2 mixed gases on friction coefficients and wear resistance of DLC films were investigated. The friction coefficients are lower than 0.3 when increasing the methane content up to 50%. Bonding states and film quality were characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. FTIR spectra of PC compared to the carbon films show the shift of maximum absorbency from sp3 CH3 to sp3 CH2 in the range of 2970–2920 cm−1. Single broad peak of Raman spectra appears at a wavenumber of approximately 1530 cm−1. The D-band position is shifted toward the higher frequency whereas the G-band position seems to be unchanged with the higher diluted hydrogen content. The surface roughness of the carbon films is finer than that of PC. Scanning electron microscope micrographs could not reveal clearly the distinction between morphologies of the films and PC.