Systematic variation of the Raman spectra of DLC films as a function of sp2:sp3 composition

Abstract We report the Raman spectra of a set of hydrogen-free diamond-like carbon (DLC) films prepared under conditions that result in different types of carbon bonding and for which the sp 2 :sp 3 content was independently determined by electron energy loss spectroscopy. The films were prepared using a mass selected C + ion beam deposition system covering the ion energy range 10 eV to 20 keV. Previous measurements have shown that the sp 2 component of the films decreases as the ion energy is increased from about 10 to 300 eV. For films made with ion energies in excess of 1 keV, the sp 2 component increases with increasing ion energy. The Raman spectra of these films show a broad asymmetric peak which narrows with decreasing sp 2 content. The spectra were fitted with a single skewed lorentzian peak described by the Breit-Wigner-Fano lineshape. The data presented may serve as a reference for DLC characterization. In particular, the parameters from the fits show a strong dependence on the sp 2 component of the films which may be used to identify unambiguously (hydrogen-free) DLC films of low sp 2 content (i.e. very “diamond-like” films).