FIRST PRINCIPLES STUDIES OF RAMAN SCATTERING IN LOW-DIMENSIONAL MATERIALS

Abstract

In this thesis, we use first-principle calculations to predict the Raman spectra of emerging two-dimensional (2D) material-related systems and gain insights into the electron-phonon coupling of these systems. We first focus on recently synthesized half-van-der-Waals 2D metals which are covalently bound to a SiC substrate and protected by a graphene overlayer. In contrast to conventional 2D materials, the zone-center phonon modes in these 2D metals can be strongly coupled to the SiC substrate. We use a Green’s functions approach to study the surface resonance phonon modes, and predict the resonant Raman spectra in these systems. The optical resonances in these materials are shown to follow a simple quantum well model. We next focus on the recently observed phenomena of surface-enhanced Raman spectra (SERS) in organic-2D material systems. Using first-principle calculations, we propose a new mechanism for the origin of chemical enhancement in SERS from 2D semiconducting materials.