Electronic properties of structurally modified C₆₀ films

When thin films are exposed to DEA vapour, the absorption features of C₆₀ shift to the red, most notably the charge-transfer exciton features at approx. 475nm and 525nm. Raman shows that the features of the exposed film have been shifted relative to those of the pristine film and that the film is stable against the characteristic C₆₀ photo-transformation. The behaviour is reminiscent of that observed in annealed C₆₀ films, which was shown to be the result of a partial conversion of the film to a hcp structure. That the effect of exposure to the vapour is structural is suggested by the observed microscopic cracking of the film, and is confirmed by x-ray diffraction. It is shown that there is a photostable form of solid C₆₀ whose electronic properties differ significantly from those of fcc films.