SYSTEMATIC VARIATION OF THE RAMAN-SPECTRA OF DLC FILMS AS A FUNCTION OF SP(2)-SP(3) COMPOSITION

We report the Raman spectra of a set of hydrogen-free diamond-like car bon (DLC) films prepared under conditions that result in different typ es of carbon bonding and for which the sp(2):sp(3) content was indepen dently 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 show n 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 i n excess of 1 keV, the sp(2) component increases with increasing ion e nergy. The Raman spectra of these films show a broad asymmetric peak w hich narrows with decreasing sp(2) content. The spectra were fitted wi th a single skewed lorentzian peak described by the Breit-Wigner-Fano lineshape. The data presented may serve as a reference for DLC charact erization. In particular, the parameters from the fits show a strong d ependence on the sp(2) component of the films which may be used to ide ntify unambiguously (hydrogen-free) DLC films of low sp(2) content (i. e. very ''diamond-like'' films).