First-principles study on atomic configuration of electron-beam irradiated C60film

Abstract

Density functional calculations of the atomic configuration of electron-beam irradiated C 60 thin films were implemented. By examining the electronic structure and electron-transport properties of C 60 clusters, we found that a rhombohedral C 60 polymer with sp 3 -bonded dumbbell-shaped connections at the molecule junction is a semiconductor with a narrow band gap. In addition, the polymer changes to exhibit metallic behavior by forming sp 2 -bonded peanut-shaped connections. Conductance below the Fermi level increases and the peak of the conductance spectrum arising from the t u1 states of the C 60 molecule becomes obscure after the connections are rearranged. The present rhombohedral polymer, including the [2 + 2] four-membered rings and peanut-shaped connections, is a candidate for representing the structure of the metallic C 60 polymer at the initial stage of electron-beam irradiation.