Nanoscale and mesoscale properties of nanostructured carbon films

A multi-scale investigation of nanostructured carbon films has been performed by means of inelastic light scattering (Raman and Brillouin scattering). Carbon films with different nano- and mesostructure have been deposited from supersonic cluster beams in a low energy deposition regime by exploiting aerodynamic focusing effects. Acoustic phonon propagation in the porous amorphous structure, where disorder acts as a damping factor, is investigated by Brillouin scattering. Depending on the nano- and meso-structure, acoustic phonons can either propagate along the medium, which acts as an elastic continuum at the meso-scale (i.e., hundreds of nm), or turn to overdamped oscillations localized by the structural disorder. Nevertheless, we show that it is always possible to measure the elastic constants of thin and porous films, when other techniques (e.g., nano-indentation) become critical. At the nano-scale, Raman scattering measurements show the typical structure of an amorphous carbon, where the structural disorder is affected by the primeval cluster mass distribution. The synthesis of cluster-assembled carbon films and the in situ Raman characterization in a UHV system allowed to observed the presence of a relevant fraction of sp/sup 1/-hybridized carbon chains (also know as carbynoid structure) embedded in the sp/sup 2/ amorphous network.