Elastic properties of van der Waals epitaxy grown bismuth telluride 2D nanosheets.

Bismuth telluride (Bi2Te3) two-dimensional (2D) nanosheets prepared by van der Waals epitaxy were successfully detached, transferred, and suspended for nano-indentation measurements to be performed on freestanding circular nanosheets. The Young's modulus acquired by fitting linear elastic behaviors of 26 samples (thickness: 5-14 nm) is only 11.7-25.7 GPa, significantly smaller than the bulk in-plane Young's modulus (50-55 GPa). Compliant and robust Bi2Te3 2D nanosheets suggest the feasibility of the elastic strain engineering of topological surface states.