New aspects of Raman scattering in carbon-based amorphous materials

Systematic near-infrared (785 nm) excited Raman spectroscopic investigations were performed on different a-C:H thin films. Two additional bands besides the D and G ones were decomposed in the near-infrared excited Raman spectra of these materials. The G band was found to be composed of two sub-bands with well separable dispersion behavior, indicating that the dispersion of the G band in amorphous carbons is not the shifting of a single band with excitation wavelength but, in fact, it is a selective enhancement of different components of the G band. The fourth peak located below 1200 cm −1 was assigned to vibrations of sp 2 carbon chains.