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Internal Friction and Shear Modulus of Graphene Films

We report internal friction and shear modulus measurements of several types of synthesized graphene films. They include reduced graphene oxide, chemical-vapor deposited (CVD) graphene films on thin nickel films and on copper foils. These films were transferred from their host substrate into a water bath, and re-deposited onto to a high-Q single crystal silicon mechanical double-paddle oscillator. A minimal thickness dependence of both internal friction and shear modulus was found for reduced graphene oxide films varying thickness from 4 to 90 nm and CVD graphene films on nickel from 6 to 8 nm. The shear modulus of these multilayered films averages 53 GPa. Their internal friction exhibits a temperature independent plateau below 10K. The values of the plateaus are similar for both the reduced graphene oxide films and CVD graphene films on nickel, and they are as high as the universal "glassy range" where the tunneling states dominated internal friction of amorphous solids lies. In contrast, CVD graphene films on copper foils are 90~95% single layer. The shear modulus of these single layer graphene films are about five times higher, averaging 280 GPa. Their low temperature internal friction is too small to measure within the uncertainty of our experiments. Our results demonstrate the dramatic difference in the elastic properties of multilayer and single layer graphene films.