Valence photoelectron spectra of an electron-beam-irradiated C60 film

Valence photoelectron spectra of an electron-beam (EB) irradiated C-60 film, which exhibited metallic electron-transport properties in air at room temperature, are presented. The electronic structure of the C-60 film became closer to that of graphite as the EB-irradiation time increased, and its density of states around the Fermi level was eventually greater than for the graphite. This suggests that the electronic structure of the C-60 film changed from a semiconductor to a semimetal and/or metal by EB irradiation. Interestingly, the electronic structure remained metallic even after five days of air exposure, which is the reason for the metallic electron-transport property in our previous report [Appl. Phys. Lett. 82, 595 (2003)]. (C) 2004 American Institute of Physics.