Raman spectroscopy and optical properties of amorphous diamond-like carbon films

The Raman spectroscopy and optical characterization of amorphous hydrogen-free diamond-like carbon films is described. The samples were prepared by using mass-separated carbon ion beam and pulsed arc discharge deposition methods. For the samples prepared with both deposition methods, the correlation between the sp(3) fraction and the shape of the Raman spectra was obtained. The refractive index and absorption of these films were also studied and compared with the Raman spectra, and the optical properties were found to correlate with the Raman spectra for the samples prepared with ion beam technique. The effect of interference of light on Raman spectra was found to be important for the carbon films with low absorption. The developed characterization methods were applied to study modifications of carbon film structure upon irradiation with energetic ions and thermal annealing.