INTERFERENCE-INDUCED EFFECTS IN RAMAN STUDIES OF HYDROGEN-FREE DIAMOND-LIKE CARBON-FILMS

In transparent hydrogen-free diamond-like carbon films, two types of i nterference-induced effects on Raman spectra are observed, amplitude e nhancement and spectral modification. Specific features of the interfe rence effects on Raman intensity components detected from different co nstituents of the samples, which are the film surface, diamond-like bu lk, and silicon substrate, are considered. The proportion between thes e Raman components is shown to be an oscillating function of the film thickness. A procedure to record selectively Raman scattering from bul k structure is proposed, and a discrimination factor of approx. 10(-2) for the surface scattering is experimentally demonstrated. The thickn ess dependency of the Raman intensity allows the absorption coefficien t of the bulk material to be estimated. The observed modification of t he Raman spectra influences the characterization of film microstructur e. (C) 1998 Elsevier Science S.A. All rights reserved.