The Elusive Determination of the Thermal Expansion Coefficient of Graphene

The estimation of temperature-dependent thermal expansion coefficient (TEC) of graphene is quite challenging. There exist significant disagreements within theoretical calculations and equally with the experimental estimates of this quantity, both with reference to the magnitude and sign of the TEC. The difficulty in the estimation broadly arises from the fact that not only can graphene expand or contract likes a crystal, but it can behave like a 2D elastic membrane and deform out-ofplane. In our work [1], we have investigated the temperature-dependent TEC of graphene over a temperature range 90300K using as-grown chemical-vapor deposited graphene on copper substrates by temperature-dependent Raman spectroscopy, and compared the results on other substrates. We demonstrate the importance of incorporating the strainprofile induced in graphene due to the graphene-substrate interactions [1-3] which may involve specific anisotropies. Furthermore, the role of temperature dependent Grunëisen parameter corrections is shown.