Assignment of the Raman Modes of VO2 in the Monoclinic Insulating Phase

We have studied the polarized Raman scattering of VO2 thin film in the low-temperature monoclinic insulating phase. We found that the Raman spectra showed distinctly different characters between the parallel and the cross configurations with respect to the (010) surface of the VO2 thin film. These distinctly different characters enabled us to make a relatively direct assignment of the observed Raman modes. Our results first suggested all nine A(g) and nine B-g Raman active modes that are predicted by group theory. We also compared our assignment of the Raman modes with those in earlier reported studies; our discussion indicates that our assignment more precisely presents the symmetries of the observed Raman modes.