Renan Da Paixão Maciel: Interface-Controlled Spintronics: A DFT Approach from Graphene to Bi-Based Nanostructures

Abstract

This thesis presents a comprehensive theoretical investigation of two-dimensional (2D) materials, focusing on the electronic properties of graphene and bismuth-based compounds, such as the BiAs monolayer. Using Density Functional Theory (DFT), this thesis aims to explore how external factors, including strain, doping, and interface engineering, impact the electronic behavior of these materials. For graphene, the study focuses on the effects of AlOx metal-oxide deposition on its surface, emphasizing how interface-induced phenomena, such as controlled sp3 defect formation, modify its electronic band structure. The theoretical modeling of the graphene/alumina interface shows that surface engineering enhances the performance of graphene-based spintronic devices and provides insights for developing resistive switching devices for neuromorphic computing. For bismuth-based materials, this work provides a theoretical investigation of the BiAsmonolayer, emphasizing its electronic properties and its potential as a topological insulator. Using DFT, this thesis explores the interplay between spin-orbit coupling and structural inversion asymmetry in BiAs, which leads to a pronounced Rashba spin splitting. Two distinct scenarios are considered: BiAs grown on an InAs substrate and its free-standing form unaffected by substrate interactions. For the substrate-supported case, this study discusses the first experimental synthesis of BiAs and its electronic characterization. For the free-standing form, the focus shifts to the effects of biaxial strain on its band structure, revealing a strain-induced topological phase transition and the coexistence of Dirac-like states and Rashba-split bands.