Polymerization of C60 fullerene thin films by UV pulsed laser irradiation

Abstract Fullerene C 60 thin films were grown by physical vapor deposition (PVD) onto Si (1 0 0) substrates at room temperature in a vacuum chamber kept at 10 −6  Torr. Photopolymerization of C 60 was performed by irradiation with a pulsed Kr-F laser. The films obtained at a fluence of 25 mJ/cm 2 were no longer soluble in toluene, indicating the conversion of C 60 into a different solid phase. IR spectra of the irradiated films exhibit several new intense modes indicating the lowering of fullerene molecule symmetry. At the same time, the characteristic modes of pristine C 60 had reduced intensities or disappeared, indicating the contribution of sp 3 -bonding. Raman spectra of the modified C 60 films showed the lowering of C 60 symmetry as well, along with the increasing disorder due to sp 3 carbon atoms. The highest applied irradiation of above 30 mJ/cm 2 resulted in the broadening of G and D-bands related to the amorphous carbon phase. The optimal experimental conditions for fullerene photopolymerization for areas larger than 1 cm 2 , reducing the undesirable formation of other carbon phases, were found.