Raman scattering study of highly fluorinated graphite

Raman spectra of highly fluorinated CxF samples (1 < x < 2) prepared at room temperature and 515 degreesC were measured. CxF samples prepared at room temperature exhibited two Raman bands at 1593-1583 and 1555-1542 cm(-1). Graphite samples fluorinated at 515 degreesC for 1 and 2 min also gave similar bands at 1581-1580 and 1550-1538 cm(-1). However, graphite samples fluorinated from 15 min to 10 h at 515 degreesC no longer showed such spectra. The Raman peaks shifted to lower frequencies with increasing fluorine concentration in CxF. This trend is due to the weakening of the C-C bonds of the graphene layers. Observation of both kinds of Raman bands suggests the coexistence of two highly fluorinated phases, C2F and C1F, in the samples. The process of formation of graphite fluoride is discussed on the basis of the Raman spectra of CxF samples obtained at 515 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.