Estudo de propriedades estruturais e óticas de heteroestruturas formadas com materiais bidimensionais

Abstract

In this thesis we describe the fabrication of two-dimensional materialheterostructures for the study of structural and optical properties. Our results show that it is possible to build heterostructures with well-defined interfaces in which twodimensional materials are integrated. Two invependent methods were used. The first method consists in rolling thin films to produce InGaAs/Cr/Graphene micro- and nanotubes. In such system the interactions and structural properties of single and multilayer graphene inserted into cylindrical heterostructures are investigated. We were able to retrieve elastic constant values for graphene through a method that imposes homogeneous and non-local curvature. We show that curvature effects solely do not modify the Raman signature of graphene down to a lower limit of 600 nm radius. The second method uses a discrete atomic layer transfer system that is used to build Van der Waals heterostructures of exfoliated two-dimensional materials such asgraphene on hexagonal boron nitride (hBN). We present scattering-scanning near-field optical microscopy (s-SNOM) results in the infrared region that allow the study of optical properties of these structures with emphasis on the effects generated by polaritons. Two distinct polariton propagation phenomena are well known in thegraphene/hBN system: (i) surface plasmon-polaritons (SPP or SP2) on graphene and hyperbolic phonon-polaritons (HPP or HP2) on hBN. We describe the observation of mode hibridization, resulting on specific graphene/hBN heterostructure modes. These modes are named surface plasmon-phonon polaritons (SPPP) and are induced by electron density oscillations on graphene and lattice vibrations on hBN.