Brillouin scattering from C70 and C60 films: a comparative study of elastic properties

Brillouin scattering measurements carried out on a thin film of C70 deposited on a Si(1 0 0) substrate show modes at 4.8 and 25 GHz due to the surface Rayleigh wave and the bulk longitudinal acoustic mode, respectively, the corresponding modes for C60 being found at 4.3 and 30 GHz. Based on the Brillouin data, the values of the bulk, shear and Youngʹs moduli of C70 are found to be 11.3, 3.2 and 8.7 GPa, respectively (the corresponding values for C60 are 14.9, 4.7 and 12.7 GPa). Poissonʹs ratios for C70 and C60 are comparable, the values being 0.37 and 0.36, respectively.