Computational Studies of 2D Materials : Application to Energy Storage and Electron Transport in Nanoscale Devices

Abstract: The field of two-dimensional (2D) layered materials provides a new platform for studying diverse physical phenomena that are scientifically interesting and relevant for technological applications. Novel applications in electronics and energy storage harness the unique electronic, optical, and mechanical properties of 2D materials for design of crucial components. Atomically thin, with large surface to volume ratio, these materials are attractive for broad applications for hydrogen storage, sensing, batteries and photo-catalysis. Theoretical predictions from atomically resolved computational simulations of 2D materials play a pivotal role in designing and advancing these developments.The central topic of this thesis is 2D materials studied using density functional theory and non-equilibrium Green’s function. The electronic structure and transport properties are discussed for several synthesized and predicted 2D materials, with diverse potential applications in nanoscale electronic devices, gas sensing, and electrodes for rechargeable batteries. Lateral and vertical heterostructures have been studied for applications in nanoscale devices such as graphene/hBN heterostructure nanogap for a potential DNA sequencing device, while in case of twisted bilayer black phosphorus nanojunction, where electronic and transport properties have been explored for diode-like characteristics device. We also have addressed the structural, electronic and transport properties of the recently synthesized polymorphs of 2D borons known as borophenes. We have explored the conventional methods of tuning the material’s properties such as strain in borophene and substitutional doping in black phosphorus with the further investigation of their gas sensing application.A significant portion of this thesis is also dedicated to the energy storage applications of different 2D materials. Energy storage technologies arise with vital importance in providing effective ways to transport and commercialize the produced energy, aiming at rechargeable batteries with high energy and power density. In this context, first-principles simulations have been applied together with other theoretical tools to evaluate structural properties, ion intercalation kinetics, specific capacity and open circuit voltage of selected 2D materials at the atomic level. The simulation study supports the understanding while improving the properties of the materials to increase their efficiency in battery operation.