Internal friction study on C₆₀ film

We report the study of the internal friction of C60 polycrystal films with different grain size (50 ∼500nm) measured at the frequency ranged from 270 to 3140 Hz. At around 260K, an λ-shaped internal friction peak and a modulus drop corresponding to the order-disorder phase transition are observed. With the decrease of grain size, the height of the Q1 peak and the magnitude of the modulus drop increase. The height of the Q-1 peak is found to be proportional to the measurement frequency. The λ-shaped internal friction peak may be attribute to the fluctuation of new phase embedded in the old phase. The large amount of boundaries in the crystal of little grain size will improve the rate of nucleation of new phase and the peak will become higher. The magnitude of the modulus drop blow 260 K is proportional to the measurement frequency , while above 260 K , the modulus is frequency independent.