Ricerc@Sapienza

The isolation of graphene -a single layer of carbon atoms- in 2004 opened the door to a flourishing field of research and nowadays a plethora of other two-dimensional (2D) crystals have been discovered. These materials are characterised by a layered structure in the bulk form, where the different layers are kept together via weak van der Waals (vdW) forces. Due to these weak bonds, it is possible to isolate single layers of the material and unique phenomena arise, stemming from the lowered dielectric screening and enhanced quantum effects. These 2D crystals are all incredibly flexible and robust, and feature diverse electronic properties, including insulating (e.g., boron nitride), semiconducting (e.g., WS2, MoS2, WSe2, MoSe2, MoTe2), semi-metallic (e.g., graphene, WTe2) and superconducting (e.g., NbSe2, ReS2) materials. The great interest attracted by these crystals in the past decade is now moving a step forward, towards the creation of 2D heterostructures. While the fabrication of conventional heterostructures suffers from lattice mismatch constraints, 2D crystals stack together via vdW interactions, that allows an unprecedented tunability. The exploration of this wide field has just commenced, and novel heterostructures with alluring characteristics could be created by assembling crystals with different electronic properties. This project aims at the fabrication and study of a variety of 2D heterostructures, and the effect of hydrogen-irradiation in these systems will also be addressed. The heterostructures will be characterised by Raman, photoluminescence, non-linear optics studies and carriers' lifetime studies. Hydrogen-irradiation treatments in bulk vdW crystals led to the formation of hydrogen-filled bubbles on the sample surface and provided a means to strain these materials. Here, we propose to exploit irradiation processes to develop strain-engineering protocols in 2D heterostructures and to study how strain affects their opto-electronic properties.