Propriedades eletrônicas e de transporte em nanoestruturas de metais de transição dicalcogenados

Abstract

In this thesis we study the electronic and transport properties of heterojunctions formed by di erent layers of distinct types of TMDCs, which are three-dimensional materials composed of triatomic layers of type MX2, where M represents an atom of the transition metal family and X represents a atom of the calcogens family. We use the Density Functional Theory (DFT) functional theory for the study of the electronic properties of the systems considering MoS2, MoSe2, WS2 and WSe2 whose band structure is semiconductor and NbS2, NbSe2, CoS2 and CoSe2 which are metal TMDCs. Having these characteristics as a base, vertical heterojunctions formed by a metallic layer stacked under a semiconductive layer were hypothesized. This double con guration is what we know as bilayer. Heterojunctions formed by metallic layers were also studied. In the model used in this thesis for electronic structure was considered the contribution of spin to the structure of bands. The results show that spin has considerable relevance pointing to this type of structure as a potential candidate for applications in the emerging branch of spintronics in the future. In addition, from the original bilayers were constructed models for the study of the electronic transport in the transverse direction to the plane of the layers. For this, the formalism of Landauer-B uttiker was used for ballistic transport. The results for the quantum conductance showed that it is strongly dependent on the spin components, also showing a diode behavior, not only in the metal-semiconductor junction but also in the metal-metal junction. Finally, it has also been investigated how the electronic properties of a MoS2 trilayer are modi ed when it is subjected to an axial stress.