Mechanism to Generate Larger Strain in Two-Dimensional Materials*

Two-dimensional (2D) materials, especially graphene, are very sensitive to strain due to every atom residing at the surface. Theory predicts that when graphene experiences large strain, its electronic properties change dramatically. In particular for strain in excess of 20% a strain-dependent gap is expected to develop in its band structure, providing a mechanism to switch its transport properties on and off. Thus far however strain levels achieved with standard techniques could not exceed a few percent. We present a piezoelectrically controlled technique that can introduce, in a controlled way, a continuously variable amount of uniaxial strain in 2D materials reaching up to ~25% where graphene ruptures.