Electronic and electron-transport properties of peanut-shaped C₆₀polymers

Abstract

When a C60 film is irradiated with a 3-kV electron-beam (EB), a peanut-shaped C60 polymer with metallic properties is formed. Valence photoelectron spectra of the polymer indicated that the density-of-states (DOS) of the polymer clearly comes across the Fermi edge in a manner similar to that of Au film used as a reference. Interestingly, the spectral function of the peanut-shaped polymer around the Fermi edge resembles that of quasi one-dimensional (1D) materials such as K0.3MO3 with its metallic phase. This suggests that the peanut-shaped polymer has also a quasi 1D structure and may exhibit the Peierls transition at a given temperature. If the polymer shows the metal-insulator transition at the given temperature, the transition would change the electron-transport mechanism of the polymer. Then, we examined the temperature-dependence of the electrical conductivity of the polymer in the range of 9K-400K. It is found that the electron transport mechanism was changed at approximately 90 K, suggesting that the valence electronic structure around the Fermi edge was changed at this temperature.