Two-dimensional periodic arrangement of one-dimensional polymerized C60 evidenced by high-resolution cryo-transmission electron microscopy

We have observed an electron-beam (EB) irradiated C60 single crystal (SC) film, using high-resolution cryo-transmission electron microscopy (cryo-HRTEM) measured at a low temperature of 80 K, and obtained the lattice images of one-dimensional (1D) C60 polymer. The intermolecular distance between adjacent C60 molecules of the 1D polymer was obtained to be 0.92 nm, which is in good agreement with the previous result of 0.93 nm estimated from the electron diffraction (ED) patterns obtained at room temperature. Although the previous work indicated that the 1D C60 polymer is explained by a mixture of body-centered orthorhombic (BCO) and hexagonal-closed pack (HCP) models, the present cryo-HRTEM images and their fast Fourier-transformed patterns clearly exclude the BCO model, and demonstrate that the 1D C60 polymer structure can be explained only by the HCP-monoclinic model.