Thermal stability of diamond-like carbon films with added silicon

Diamond-like carbon (DLC) films with added silicon content from 0 to 19.2 at.% were deposited using r.f. PECVD (radio frequency plasma enhanced chemical vapor deposition). Fourier transform IR (FTIR) spectrometry, Raman spectrometry and X-ray photoelectron spectrometry (XPS) were used to determine the structural change of the annealed DLC films in ambient air. By increasing the annealing temperature the CH_n and Si–H groups in the FTIR spectra decrease because of hydrogen evolution, whereas the intensities of CO and Si–O peaks increase owing to oxidation. From Raman spectra, the integrated intensity ratio I_D/I_G of the pure DLC films and the silicon-doped films increases at 300 and 400 °C, respectively, whereas the observable shoulder of the D band occurs at 400 and 500 °C, respectively, which indicates that the addition of silicon improves the thermal stability of DLC films. Using XPS analysis, a surface reaction for the annealed films is investigated.