Formation process and electron-beam incident energy dependence of one-dimensional uneven peanut-shaped C60 polymer studied using in situ high-resolution infrared spectroscopy and density-functional calculations

A 3 kV electron-beam irradiation of a C-60 film gives rise to formation of one-dimensional (1D) uneven peanut-shaped C-60 polymer with a cross-linked structure close to that of the P08 C-120 stable isomer obtained from the general Stone-Wales rearrangement. In this study, we examined the evolution of infrared (IR) spectra of C-60 films with respect to electron beam (EB) irradiation time, using in situ high-resolution IR spectroscopy and first-principles density-functional calculations, and found semi-quantitatively that the 1D uneven peanut-shaped C-60 polymer is formed via intermediate polymers with a cross-linkage close to that of P04 and P06 C-120 isomers obtained from GWS rearrangement. In addition, we examined the dependence of EB-induced C-60 polymerization on an incident energy of EB in the range 3-7 kV. IR spectra obtained for 5 and 7 kV EB irradiation of C(60)films showed the same product as for 3 kV EB irradiation. However, when 5 and 7 kV EBs continued to irradiate C-60 films for a long time after the polymer formation, the 1D peanut-shaped polymer did not proceed to become 1D polymers with a more coalesced linkage than that of the P08 one but was destroyed to become amorphous carbons.