Interference-induced effects in Raman studies of hydrogen-free diamond-like carbon films

In transparent hydrogen-free diamond-like carbon films, two types of interference-induced effects on Raman spectra are observed, amplitude enhancement and spectral modification. Specific features of the interference effects on Raman intensity components detected from different constituents of the samples, which are the film surface, diamond-like bulk, and silicon substrate, are considered. The proportion between these Raman components is shown to be an oscillating function of the film thickness. A procedure to record selectively Raman scattering from bulk structure is proposed, and a discrimination factor of approx. 10(-2) for the surface scattering is experimentally demonstrated. The thickness dependency of the Raman intensity allows the absorption coefficient of the bulk material to be estimated. The observed modification of the Raman spectra influences the characterization of film microstructure. (C) 1998 Elsevier Science S.A. All rights reserved.