Temperature dependence of the Raman spectra of polycrystalline graphene grown by chemical vapor deposition

The temperature dependence of the Raman spectra in the temperature range between 298 and 673 K was investigated for polycrystalline monolayer graphene films with defects, such as domain boundaries, synthesized by chemical vapor deposition. The Raman frequencies of G and 2D bands monotonically decrease with increasing temperature. The reversible change in the band frequencies is observed during thermal cycling after the first heating. From the reversible change, the temperature coefficients of G and 2D band frequencies are estimated to be −0.024 and −0.043 $cm−1/K$⁠, respectively. These values are small compared with those for mechanically exfoliated ones without defect reported previously. Furthermore, the magnitude of the temperature coefficient of the G band decreases with increasing defect density. The smaller temperature coefficients can be explained by the suppression of anharmonic phonon interactions due to the defects.