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 sp(3) bond prefers higher microwave power. DLC films prepared at target voltage of -200 V have higher sp(3) content than that of -350 V, moreover, an increase of gas pressure during experiments yields higher sp(3) content at the microwave power below 270 W, whereas the change of sp(3) content is slight with the various conditions when microwave power exceeds 270 W.