[en] Short-range structural and chemical ordering in Si-rich chemically deposited a-Si_1-xC_x thin films have been investigated via Raman scattering and the numerical modelling technique. Raman spectra have been presented over a wide frequency range including both Stokes and anti-Stokes scattering. The interpretation of the spectra is performed in terms of the whole density of vibrational states. In order to determine the latter, the structure of the a-Si_1-xC_x (x<0.5) system has been modelled and the corresponding dynamical properties have been computed in the harmonic approximation using the valence-force-field model. By integrating the Stokes and anti-Stokes, first-order, and multiple-order processes, a fit of the experimental Raman spectra has been achieved. As expected, our analysis shows a tendency to chemical ordering into a tetrahedrally coordinated network for Si-rich alloys. Nevertheless, a total chemical ordering is not achieved since homonuclear C-C bonds coexist with Si-Si and Si-C ones in these alloy compounds. (author)