a, Raman spectra with measurement temperature cycled from 10 K to 300 K and from 300 K to 10 K. The Raman frequency of the G band (ωG) and 2D band (ω2D) is plotted against the variable temperature, demonstrating that the coupling interactions are recovered and this variable-temperature measurement is non-destructive. b, Raman frequency shift for graphene films grown on Cu(111) by traditional CVD, before and after ICP treatment, and related FWHM of G and 2D bands and IG/I2D for the above spectra, showing that FWHM is slightly changed but the I2D/IG seems almost unchanged; Raman frequency shifts are also shown for as-grown graphene films on Cu(111) by ICP–CVD and on Cu foils by traditional CVD. c, Ex situ AFM height profiles for as-transferred and UHV-annealed graphene films. The thickness is decreased by about 5 Å after this UHV annealing. Insets are related AFM height images. In situ variable-temperature Raman measurements are also shown for the transferred and UHV-annealed films on SiO2/Si wafers, together with related ΔωG and Δω2D. Scale bars, 2 μm. d, Raman spectra of the transferred graphene on Cu(111) under different UHV annealing conditions, and in situ variable-temperature Raman spectra of as-transferred graphene films before (25 °C) and after UHV annealing at 180 °C and 430 °C. The variable temperatures are all from 10 K to 300 K.