PROFESSOR @UNIVERSITY OF ROME SAPIENZA, PHYSICS DEPARTMENT
The discovery of graphene brought evidence of the new physical properties of a bulk crystal when thinned down to single atomic layer, stimulating the study and manufacturing of truly bidimensional (2D) materials. Since then, attention focused on the wide class of van der Walls (vdW) materials, i.e. layered systems characterized by strong bonding within the plane and weak vdW force between them.
After a brief review of the most important 2D materials nowadays under intense investigation, I will focus on Transition Metal Dichalcogenides (TMDs). Like graphene, TMDs can be easily thinned from bulk to few/single layers but, differently from it, conductive properties of TMDs can vary from metallic to semiconducting character. Experiments and calculations show a marked dependence of TMDs peculiar electronic and optoelectronic properties on the number of layers and a large degree of tunability of the electronic bands. Indeed, the intrinsic width of the plane, the possibility of using different chemical species and of assembling heterostructures (HSs) of different TMDs, provide many degrees of freedom for properly tailoring desired physical properties. I will discuss different spectroscopic results recently obtained on TMDs, with a particular attention to the effect induced by very high pressure that represents an additional parameter to tune the bandgap, thus controlling the electronic properties.