Dose dependences of the optical properties of fullerene films subjected to the electron irradiation

The optical conductivity σ( E) in the energy range of interband transitions in the C 60 films subjected to the high-energy electron irradiation (E e = 1,8 MeV) was studied by the method of spectral ellipsometry for the different doses of absorption ( Q = 1,5; 4 and 8 MGy). A change in the crystal and vibrational structure of these samples was investigated by the X-ray diffraction method and Raman spectroscopy. It was shown that the noticeable transformations of electron structure are observed depending on the dose of absorption. An increase of electronic concentration in the entire region of interband transitions with the σ( E) nature retention, peculiar to the nonirradiated samples, occurs under the small doses ( Q = 1,5 and 4 MGy). The σ( E) changes under these doses are explained as the consequence of the transfer of charges from the displaced carbon atoms to the fullerene molecules as a result of their radiation damages. An increase in the dose of absorption to Q = 8 MGy indicates the beginning of the degradation of C 60 molecule structure.