Ultraviolet photoelectron spectra of C₈₄ and K_xC₈₄

Ultraviolet photoelectron spectra of C₈₄, one of the fullerene family compounds, and of potassium-dosed C₈₄ have been measured with synchrotron radiation. The spectra of C₈₄ are compared with those of C₆₀ and C₇₀. The photoemission spectral onset of C₈₄ is 1.3 eV below the Fermi level, which is smaller by 0.5 eV than that of C₆₀ or C₇₀. This indicates its small band gap, which was expected from its absorption spectra. Upon potassium dosing, a new band becomes distinct between the Fermi level and the highest occupied molecular orbital band. The new band edge does not cross the Fermi level, which indicates that potassium-dosed C₈₄ is not metallic but a semiconductor.