Interplay between Raman shift and thermal expansion in graphene: Temperature-dependent measurements and analysis of substrate corrections

Measurements and calculations have shown significant disagreement regarding the sign and temperature variations of the thermal expansion coefficient (TEC) of graphene alpha(T). Here we report dedicated Raman scattering experiments conducted for graphene monolayers deposited on silicon nitride substrates and over a broad temperature range extending over 150-800 K. The relation between those measurements for the G band and the graphene TEC, which involves correcting the measured signal from the mismatch contribution of the substrate, is analyzed based on different theoretical candidates for alpha(T). Contrary to calculations in the quasiharmonic approximation, a many-body potential reparametrized for graphene correctly reproduces experimental data, suggesting that the TEC is more likely to be positive above room temperature.