SYNTHESIS OF DIAMOND NANOCRYSTALLITES USING THE LOW-ENERGY CLUSTER BEAM DEPOSITION - AN INDIRECT PROOF OF SMALL FULLERENE EXISTENCE

Using a laser vaporization source, we have deposited low-energy neutral carbon clusters in the range C-10-C32 in order to grow thin films (e almost-equal-to 100 nm). Compared to common DLC films, the first-order Raman spectrum does not give at all the same results, since it does not exhibit the usual G and D bands, but is comparable to the vibrational density of states of diamond. However, unlike amorphous covalent materials, a fine structure due to a perfect short range order is observed. Furthermore, we measure a large red shift (about 110 cm-1), which can be related to the decrease of the material force constants compared to the diamond ones. Finally, taking into account the specific nucleation and growth mechanisms involved in the low-energy cluster beam deposition as well as the crystallographic and electronic structures of our films, the hypothesis of small fullerene formation (C20-C32) in the nonequilibrium conditions of the laser vaporization source seems conceivable.