Graphene Bimetallic-like Cantilevers: Probing Graphene/Substrate Interactions

The remarkable mechanical properties of graphene, the thinnest, lightest, and strongest material in existence, are desirable in applications ranging from composite materials to sensors and actuators. Here, we demonstrate that these mechanical properties are strongly affected by the interaction with the substrate onto which graphene is deposited. By measuring the temperature-dependent deflection of graphene/substrate "bimetallic" cantilevers we determine strain, thermal expansion coefficient, and the adhesion force acting on graphene films attached to a substrate. Graphene deposited on silicon nitride (SiNx) is under much larger strain, epsilon(g) similar to 1.5 x 10(-2), compared to graphene on gold (Au), epsilon(g) < 10(-3). The thermal expansion coefficient alpha(g) of graphene attached to SiNx is found to be negative, in the range from (- 5... - 1) x 10(-6)K(-1) and smaller in magnitude than alpha(g) of suspended graphene. We also estimate the interfacial shear strength of the graphene/SiNx interface to be similar to 1 GPa at room temperature.