Tuning graphene dynamics by mechanical strain

Abstract

Two-dimensional (membrane) materials have been receiving much scientific attention due to their unique material properties that can be used to study the smallest physical phenomena. One such material is graphene, perceived as the holy grail in material physics, due to its unique material properties. Its aspect ratio diminishes the bending rigidity and allows wrinkles, ripples and other morphological imperfections to dominate the mechanical behaviour. Applying tension is a necessity to control these geometrical imperfections and simultaneously opens up pathways to study physical phenomena such as magnetism, superconductivity, optics and much more. Typically, this tension is applied using electrostatic forces, which alters amongst others, the electric properties of the material. Mechanically applied tension offers a solution to this problem but comes at the cost of difficult manufacturability. In this work, a new method to incorporate 2D materials with N/MEMS is presented. The dynamics of mechanically tensioned graphene are probed in linear and nonlinear regimes. The former regime finds the exact opposite of what is observed in electrostatically tensioned membranes. The latter shows exotic nonlinear effects that can be tuned by applying tension. Furthermore, it is identified that the dynamics of the MEMS device are coupled to that of the resonating membrane despite their mass and stiffness being roughly five orders of magnitude apart. The bottleneck of this project is the adhesion force between the two is insufficiently strong to apply significant strain allowing slippage to occur.