Laser Shock Nano-Straining in 2D Materials

Straining nanomaterials to break their lattice symmetry is perhaps the most efficient approach toward realizing bandgap tunability. Graphene has a great potential to replace silicon in prospective semiconductor industries due to its outstanding electronic and transport properties; nonetheless, its lack of energy bandgap is a substantial limitation for practical applications. In this talk, a large-scale strain engineering technique to control the local strains in 2D materials and their heterostructures will be discussed. First, laser shock nanostraining will be introduced to generate three-dimensional (3D) nanostructures and thus induce local strains in the graphene sheet. The size dependent straining limit of the graphene and the critical breaking pressure will be discussed. Moreover, laser shock nanostraining induces modulated inhomogeneous local asymmetric elastic–plastic strains as results of 1-100 GPa-level shock loading at a high strain rate of 10⁶–10⁸ s⁻¹. Currently, due to the weak lattice deformation induced by uniaxial or in-plane shear strain, most strained graphene studies have yielded bandgaps <0.5 eV, laser shock nanostraining can induce tunable bandgaps in graphene of up to 2.1 eV. Finally, laser shock nanostraining will be discussed to controllably tune the interlayer distance between VdW heterostructures and generate strain coupling between layers. The strains in the 2D heterolayers, providing a simple and effective way to modify their optic and electronic properties.