Dielectric properties of fullerene films

We report the study on the dielectric properties of C-60 films by means of capacitance and dissipation factor measurements at temperatures between 5 a nd 325 K. In addition to the structural phase transition at 260 K, we have observed a clear anomaly at T = 90 K, which did not show up in previous die lectric studies. This result confirms the fact that a glass transition exis ts due to the freezing in of orientational disorder in C-60. A Debye-like r elaxation in the dielectric response has also been observed, and the relaxa tion rate is thermally activated with an energy of about 277 meV, which is in good agreement with that obtained from other measurements. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)04903-7].