The new standard for Raman spectroscopy of graphene over extreamly high biaxial strain.

Most conventional methods to measure the mechanical properties of 2D materials and thin films is nanoindentation using atomic force microscopy (AFM). Herein, we report the experimental process as well as measurement of Raman spectrum (G, 2D peak, respectively) of suspended graphene under the extremely high biaxial (e.g., isotropic) strain using AFM-Raman combined tool. In our nano-indentation, the Raman peaks shifting in G and 2D were founded to be 256 cm^-1, and 675 cm^-1, respectively, for suspended monolayer graphene. The bigger advantage is that our experiment is a method that can be repeatable and simultaneously extremely high strain. Moreover, relation between shifts (G, 2D peak) and strain (%) obtained through FEM simulation show a new standard to optical property of strained graphene.