Raman scattering fromVO2single crystals: A study of the effects of surface oxidation

${\mathrm{VO}}_2$ single crystals were studied in an effort to resolve the differences that are present in two previous reports on the Raman spectra of ${\mathrm{VO}}_2$. We find that surface oxidation effects that change the stoichiometry of the material at the surface layer produce large shifting of the Raman spectral peaks. The experimental evidence is presented and the relation to the previous Raman studies of ${\mathrm{VO}}_2$ are discussed.