Strain-driven patterning of two-dimensional materials
In two-dimensional (2D) crystals, mechanical deformations turn out to be a powerful tool to control the material's properties thanks to the strong interplay between the lattice and the electronic band structure.
Here, we focus on a novel route to strain-tune the electronic properties of transition metal dichalcogenides (TMDs), a class of layered semiconductors with chemical formula MX2 (where M: W or Mo and X: S or Se) that can be exfoliated down to a single X-M-X layer. Our method is based on the capability to deform at the micro- and nano-scale a single X-M-X plane due to the deliberate trapping of molecular hydrogen in between adjacent layers in bulk flakes. Specifically, by proton irradiation we create atomically-thin TMD domes filled by H2 with internal pressure ~10 atm. The domes feature intense light emission and can be site- and size-controlled from 10000 nm to 50 nm. Here, we aim at a detailed characterization of the electronic properties of single and ensembles of WS2, WSe2, MoS2 and MoSe2 domes by spatially-resolved (500 nm resolution) photoluminescence, Raman scattering, photon-correlation and second-harmonic generation spectroscopies. X-ray photoemission spectroscopy of the M and X elements will monitor the decoupling of the upper TMD layer from the underlying parent substrate and provide information about the structural modifications caused by the lattice deformation ensuing the gas internal pressure. The goal of this project is twofold. First, we will address open issues regarding the electronic structure of strained 2D TMDs and hence explore the attainment of quantum confinement effects for the realization of single-photon sources at room temperature. Second, these studies will be instrumental for advanced investigations by photoemission spectromicroscopy (spatial resolution