Preparation and vibrational modes of C60·2CHBr3

By preparing a field-effect transistor (FET) on C60 single crystal, Sch鰊 et al.1] realized the hole-doped C60 and observed the superconductivity at 52 K. After CHBr3 molecules were intercalated into the crystal, the transition temperature increased up to 117 K2]. This finding made the fullerite to be one of the highest-Tc superconductivity materials. In order to clarify the mechanism for the increase of Tc from 52 K to 117 K, the studies of the crystal structure, the density of electr…

Preparation and vibrational modes of C60 · 2CHBr3

C60·2CHBr3 polycrystalline powder was prepared by the solution method. The vibrational modes of the sample were studied by Raman scattering and infrared adsorption techniques. The Raman spectra showed that the Ag modes were downshifted by 4-5 cm1, while the Hg(1) mode was unshifted. The analyses of the downshifts of the Ag modes revealed that a small amount of electrons were transferred from the hydrogen atoms to the C60 molecules. In the infrared spectra, the F1u modes of the pristine C60 were unshifted after the intercalation with CHBr3. However, the vibrational modes of CHBr3 changed remarkably. The C-Br stretching mode was downshifted by ～4 cm1. The adsorption of the C-H twisting mode was weakened obviously, and the adsorption of the C-H stretching mode was not observed. These results exhibited that there were nonnegligible interactions between CHBr3 and C60 molecules, and that the strongest interaction took place between the hydrogen atoms and the C60 molecules. The interaction should induce not only the changes of the vibrational modes reported here, but also those of the electronic states. So this work should offer important glues to the mechanism of the superconductivity at 117 K of the field-doped C60·2CHBr3.