Transformações estruturais e eletrônicas em nanomateriais bidimensionais sob pressão

Abstract

With the fast advance in the techniques of synthesis and characterization of two-dimensional materials, there is a rising demand for theories which allow the study and prediction of these structures. One of the most successful theories in this field is the Density FunctionalTheory, which allows the description of systems with unit cells with hundreds of atoms. We seek in this dissertation to study the electronic and structural properties of materials obtained in laboratories by our experimental collaborators. First, we study a metalsemiconductortransition that takes place when heterostructures of graphene over boronnitride are submitted to pressure in an atomic force microscopy experiment. Second, we study the formation of diamond-like structures in multi-layers of graphene that are submitted to a high-pressure Raman spectroscopy experiment. And lastly, we investigate the behavior of a structural defect in such structures, named nitrogen-vacancy center,and its possible application in biological systems and quantum information. In summary, using theoretical models we found structures that have electronic behavior in excellent agreement with the experimental results, both for graphene on boron nitride and for the diamond-like two-dimensional structures. The theoretical results reinforce the feasibility of using nanodiamonds with nitrogen-vacancy center, since they present a phenomenology similar to that obtained for the bulk phase.