Elasticity study of the irradiation-induced polymerization and decomposition of C60 solid

We investigated the polymerization and decomposition of C60 solids by high-energy ion irradiation. Young's modulus of the films showed a slight increase after irradiation with 15 MeV C4+ ions at a dose of 1 × 1013 ion cm−2. Relaxation and lambda-shaped peaks were observed at approximately 135 and 250 K, respectively, in the internal friction; these almost disappeared at a dose of 1 × 1015 ion cm−2. We concluded that the polymerization of C60 and the local destruction of the face-centered cubic (FCC) structure proceed concurrently on irradiation, and the structural phase transition at 250 K is suppressed after irradiation with doses greater than 1 × 1015 ion cm−2.