Raman spectra of amorphous carbon films deposited by SWP

Amorphous carbon film is one of the most important anti-reflection protective films coated on infrared optical components. In this paper, hydrogen-free amorphous carbon films were deposited by new type surface-wave-sustained plasma (SWP) source with a graphite target at various experiment parameters. The laser Raman spectroscopy at wavelength of 514 nm was used to investigate the structure and bonding of these carbon films. The results showed consanguineous correlations between the intensity ratio I _D/I_G and the experiment parameters such as microwave power, target voltage and gas pressure applied to the SWP source. Raman spectra proved the structure of these carbon films prepared by SWP technique is typical diamond-like carbon (DLC). The analysis on G peak position and intensity ratio I_D/I_G indicated that Raman shifts moves to low wavenumber and I_D/I_G decreases with the increasing of microwave power from 150 W to 330 W. These results means the formation of sp³ bond prefers higher microwave power. DLC films prepared at target voltage of -200 V have higher sp³ content than that of -350 V, moreover, an increase of gas pressure during experiments yields higher sp³ content at the microwave power below 270 W, whereas the change of sp³ content is slight with the various conditions when microwave power exceeds 270 W.