The intrinsic temperature effect of the Raman spectra of graphite

The Raman spectra of ion-implanted highly oriented pyrolytic graphite (HOPG ) are reported, in which an additional mode at 1083 cm(-1) and three double t structures in the positions of similar to 1350, similar to 2450, and simi lar to 2710 cm(-1) are revealed. Noticeable frequency shifts are observed f or all the Raman bands between the spectra excited with different laser pow ers, which are interpreted as the pure temperature effect and a downshift i n the C-C stretching frequency induced by the thermal expansion. Moreover, the pure temperature effect (d omega/dT)(V) without anharmonic contribution is achieved in pristine HOPG. The results suggest that the pure temperatur e effect without anharmonic contribution plays an important role in the fre quency shifts with temperature. (C) 1999 American Institute of Physics. [S0 003-6951(99)01313-3].