Theory of Electron Transport in Molecular Structures

Alshahrani, Maryam and Lambert, Colin (2022) Theory of Electron Transport in Molecular Structures. PhD thesis, Lancaster University.

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Abstract

In developing future nano-scale applications in the molecular electronics field, studies of electron transport through single molecules are of fundamental interest. Since single or multiple molecules are considered essential building blocks to design and construct these molecular electronics devices, understanding their electronic and transport properties is required. Enormous theoretical and experimental studies were carried out to make the molecular junctions and explore their electrical performance. Within this framework, this thesis addresses some of the fundamental aspects of transport theory, involving the theoretical and mathematical approaches to investigate the electron transport via junctions, including a scattering region formed from a single molecule connected to metal electrodes. The methods used in this research are based on a combination of density functional theory and its realisation within the SIESTA code, and non-equilibrium Green’s function embodied in the GOLLUM code to study electrical conductance on a molecular scale. In this thesis, I focus on various N-Heterocyclic carbenes (NHC) complexes of double NHCanchored single-molecule junctions and investigate the mechanism of charge transport through their molecular junctions. I also study their electronic structure properties, such as the wave function plot and their binding energetics to electrodes. Experimental measurements and my DFT simulations revealed a high electrical conductance of monomer and dimer NHC molecular junctions. Consequently, my simulations provide a novel strategy for designing high conductance molecular devices using NHCs and are a step along with the roadmap toward future integration of molecular electronic devices.