Comparison of Raman spectra in non-polymerized and polymerized fullerene films in the temperature range of 5-300 K

Abstract

Raman spectra of a non-polymerized and a photopolymerized fullerene films were studied at temperatures from 5 to 300 K in the range of the Ag(2) mode (1380-1500 CM-1 energy range). It was found that the curve of the temperature dependence of energy of the Ag(2) mode in the non-polymerized C60 film undergoes a kink on going through the orientation structural phase transition (TC ). In contrast to the non-polymerized film the curve of the temperature dependence of energy of monomers, dimmers, linear chains and trimers in the photo-polymerized fullerene film demonstrates the monotonic increase upon cooling. It was shown that the difference between energy of the Ag(2) mode of monomer in the photo-polymerized film and energy of the Ag(2) mode in the nonpolymerized C60 appears below TC. This difference is caused by the appearance of the structural phase transition in the non-polymerized film while this transition is absent in the polymerized film. It was found that temperature of the structural phase transition in the non-polymerized film (TC ∼ 235 K) is shifted to the range of lower temperatures in comparison with single crystal. It is expected that such temperature shift is related to impact o f a substrate on the film properties as well as possible intercalation of atmospheric O2 or N2 in octahedral cavities of fullerite.