A method for controllably inducing ultra-high strain in suspended 2D materials*

Generating strain can significantly alter the electronic properties of 2D materials. Strain-induced changes in Bandgap, Direct-Indirect gap transitions, Pseudo-magnetic fields etc. have been reported in various 2D materials. Traditional methods of inducing strain such as stretching or bending cannot produce strain values of more than a few percent on average. Here we discuss a technique for generating very high local strain in suspended 2D materials in a controlled and reversible fashion. An ultra-compact and modular device was constructed which allows a sharp STM tip to be aligned perpendicular to a 2D material suspended on micron sized pores in a Silicon Nitride mesh. This STM tip can then be used to poke and deform the suspended 2D material from one side while simultaneously monitoring the effect of the strain using various experimental probes from the other side. This opens the possibility for studying the changes in the electronic properties of Graphene and other 2D materials with local probes such as Scanning Tunneling Spectroscopy and micro Raman Spectroscopy under extreme strain conditions close to the breaking point.