Controlled Straining of Heterostructures

Graphen is a material that has attracted interest for several reasons: it is just 1 atom thick, electrically conducting and nearly transparent. What is more, graphene in its pristine, low defect form is extremely stable – at least considering it’s volume or mass. This has led to fascinating comparisons.

Colorized Scanning Electron Micrograph of a freely suspended graphene membrane (light blue) between two platin electrodes (grey). The electrodes are separated from the golden bottom gate by a 700 nm-thick polymer layer. J.O. 2016.

In order to investigate the mechanical properties of graphene it is advantagous to perform emasurements in a freely suspended geometry (see picture above), as this allows to reduce uncertainties resulting from inhomogenous attachment to the support layer.
For the investigation of its electric properties as a function of strain, however, there is a strong benefit from encapsulating graphene between two layers of isolating (hexagonal) boron nitride, as we report in a recent publication. Congratualtions, Lujun!

Wang, L.; Zihlmann, S.; Baumgartner, A.; Overbeck, J.; Watanabe, K.; Taniguchi, T.; Makk, P.; Schönenberger, C. (2019): In Situ Strain Tuning in hBN-Encapsulated Graphene Electronic Devices. Nano letters 19, 4097–4102; doi: 10.1021/acs.nanolett.9b01491.