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 × 10 14 N m −3 to 15 × 10 14 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.

Ultrafast quantitative nanomechanical mapping of suspended graphene

“…Here we present nanomechanical maps of suspended graphene taken using the PeakForce QNM imaging mode and compare extracted force curves to those measured using conventional nanoindentation/force volume mode. The force–displacement data was in agreement, and by fitting this to a simple model of a circular 2D elastic film under central point loading the Young's modulus of graphene was measured at around 1 TPa , in agreement with literature values. We also demonstrate that peak‐force imaging allows the capture of topographic data from large soft membranes with a high dynamic vertical range using non‐contact AFM, as opposed to tapping mode imaging where the tip–membrane adhesion induces oscillations in the membrane which result in triangular artifacts.…”

“…AFM nanoindentation and force volume experiments on suspended graphene are the primary way through which the mechanical properties of graphene and other two‐dimensional materials can be measured . Previous attempts to image graphene membranes using tapping mode AFM have been problematic due to the unusual combination of their high strength and high elasticity.…”

Mechanics of freely‐suspended ultrathin layered materials

“…The study of the mechanical properties of atomically thin materials typically requires the fabrication of freely‐suspended samples such as doubly‐clamped beams or circular drums. Three main approaches are employed to fabricate these suspended structures: direct exfoliation (flakes randomly distributed) onto pre‐patterned substrates with holes/trenches , etching the substrate underneath the flakes or depositing the flakes directly onto a specific hole or trench in the substrate using a transfer technique .…”

Two‐dimensional materials: From mechanical properties to flexible mechanical sensors

“…First, there is transfer of 2D materials onto prepatterned substrates with an array of holes or trenches . The flowchart of fabrications of freely suspended 2D materials is shown in Figure A.…”