Tuning $WS_2$ photoluminescence using polymeric micro-actuators in a van der Waals heterostructure.

The control of the local strain profile in 2D materials offers an invaluable tool for tailoring electronic and photonic properties of solid-state devices. In this paper, we demonstrate that strain in $WS_2$ based van der Waals heterostructures can be modulated on a local scale by means of polymeric micrometric actuators implemented by electron beam lithography directly on the growth substrate. Thanks to the underlying material structure, i.e. graphene on SiC, $WS_2$ flakes are found to slide with negligible friction, thus circumventing the technical challenges of other approaches requiring layer transfer and production of suspended membranes. As proof of concept, in our experiment we show strain-induced local modulation of the excitonic photoluminescence of such non-suspended $WS_2$ monolayers under application of custom strain profiles.