Comparison of Raman scattering in non-polymerized and photo-polymerized fullerene films at temperatures of 5-300 K

Abstract

Raman spectra of non-polymerized and photo-polymerized fullerene films are studied in the region of the A(g)(2) mode (energy range 1380-1500 cm(-2)) at temperatures of 5-300 K. The temperature dependence of the energy of the A(g)(2) mode for non-polymerized C-60 films undergoes an inflection on passing through the orientational phase transition. As opposed to the case of non-polymerized film, the energy of the monomers, dimers, linear chains, and trimers of fullerenes in photo-polymerized films increases monotonically as the temperature is lowered. It is shown that a difference in the energies of the A(g)(2) mode for the monomer in photo-polymerized films and for the monomer in non-polymerized C-60 appears below the structural phase transition temperature T-C. This difference is caused by the appearance of an orientational phase transition in the non-polymerized film (T-C similar to 235 K), while this transition is absent in the polymerized film. It has been found that the temperature of the orientational phase transition for the non-polymerized film (T-C similar to 235 K) is shifted to lower temperatures compared to the single crystal. It is proposed that this shift in the transition temperature is related to the effect of the substrate on the properties of the film, as well as to possible intercalation of atmospheric O-2 or N-2 in octahedral voids of the fullerite. Published by AIP Publishing.