RAMAN-SCATTERING OF SOLUTION-GROWN AND VACUUM-DEPOSITED C-60 CRYSTALS

Raman spectra of solution-grown C-60 crystals and evaporated films of C-60 were measured by near-infrared laser excitation and compared with spectra of a sublimation-grown C-60 crystal. Carbon disulfide and tol uene were used as solutions. Broadening of the intramolecular Raman ba nds was observed in the solution-grown crystals and evaporated films o f C-60. The broadening in the solution-grown crystals was reduced by h eat treatment after growth. A reduction in bandwidth was also found fo r C-60 films evaporated at an elevated substrate temperature. Comparis on of the Raman spectra of solid C-60 prepared under different conditi ons shows that random distribution of solvent molecules in solution-gr own crystals and structural disorder in evaporated films perturb force fields in solid C-60 and bring about inhomogeneous broadening of the intramolecular vibrational bands. It is found that the effect of the p hase transition on the Raman spectra is obscured in C-60 solids contai ning residual solvent molecules or defects.