Raman spectra of partially oriented sp2 carbon films: Experimental and modelled

Raman spectra of a thick graphitic-amorphous carbon film obtained from top-down and cross-sectional perspectives are presented and compared. The cross-sectional spectra have a prominent peak at 1450 cm−1, which is absent or not visible in the top-down spectra. From electron diffraction (ED) studies, the graphene structures in film are known to partially oriented, orthogonal to the plane of the film. On the basis of ED we present a possible structural model. We use curve fitting to indicate some possible peak assignments, which, in addition to the 1450 cm−1 peak, suggests that the cross-sectional spectra have a much smaller D peak and two other peaks at 1280 and 1400 cm−1. We use density functional theory (DFT) modelling of a range of small aromatic structures to assist in the assignment of observed Raman features to characteristic vibrational modes of structures containing carbon sheets.