Elastic and nonlinear response of nanomechanical graphene devices

Abstract

In this paper, a simple and effective experimental approach has been used to extract the mechanical properties of suspended nanomechanical graphene devices using atomic force microscopy (AFM). The main objective of this work is to study the deflection behaviour of graphene devices as a function of layer number (1–5 layers) and anchor geometry which has not been widely investigated so far. Elastic and nonlinear responses of the devices were obtained using AFM nanoindentation. The estimated linear (2.5 N m−1 to 7.3 N m−1), nonlinear spring constants (1 × 1014 N m−3 to 15 × 1014 N m−3) and pretension (0.79 N m−1 to 2.3 N m−1) for the monolayer (3.35 Å) to five layer (16.75 Å) graphene devices of diameter 3.8 µm show an obvious increasing trend with increase in graphene thickness. The effect of anchor geometry on the force versus deflection behaviour of these devices has also been investigated. The Raman spectroscopy results confirm the absence of defects in the pristine and indented devices. Using the continuum mechanics model, the Young's modulus and 2D elastic modulus of a monolayer graphene device have been found to be 1.12 TPa and 375 N m−1 respectively. The high stiffness and low mass of these devices make them well suited for sensing applications.