Investigation of the Electronic Structure of 2D Materials Using X-Ray and UV Photoemission Techniques

Abstract

The limitations of current day electronics have created a tremendous drive to find new materials for more advanced electronic devices. However, without a fundamental understanding of key interfacial processes, such as electron transfer or charge carrier dynamics, developing practical devices becomes an impossible task. It therefore is of vital importance to comprehend the fundamental physics that governs these interfacial processes to fulfill the practical need for more advanced electronic devices. In this dissertation, I mainly focus on the class of inorganic 2D materials called transition metal dichalcogenides that present a wide range of electronic properties based on their composition. I begin by exploring the ultrafast charge carrier dynamics at the interface between an organic and inorganic semiconductor (C60/WSe2). The interfacial charge transfer, which results in an interfacial electric field, reveals new opportunities to control the different spin degrees of freedom inherent to the inorganic semiconductor (WSe2) and provides a novel mechanism to create spin-polarization in a nonmagnetic heterostructure. Next, I investigate the temperature-induced electronic phase transition between the semimetallic 1T’-phase of MoTe2 and the topological Weyl semimetal Td-MoTe2. The platform provided by this phase transition constitutes a new opportunity for systematic control of the electronic structure. As a result of the more exotic electronic properties of Td-MoTe2, new scattering pathways are available and I demonstrate how the electronic structure influences the ultrafast charge-carrier dynamics in the two phases. Finally, I demonstrate the importance of the electronic structure and its influence on the luminescent properties of two types of lanthanide-doped metalorganic complexes. The energy level alignment between the ligands and the rare earth centers in the complexes determines not only the efficiency of the material’s luminescent capabilities but also its influence on the emissive color properties. Overall, the case studies presented in this dissertation highlight how the electronic structure governs the ultrafast charge carrier dynamics and electron transfer properties, presenting new opportunities towards advanced electronic devices.