Theory of electron and phonon transport in nano and molecular quantum devices:design strategies for molecular electronics and thermoelectricity

摘要

Understanding the electronic and phononic transport properties of junctions consisting of a scattering region such as a nanoscale region or molecule connected two or more electrodes is the central basis for future nano and molecular scale applications. The theoretical and mathematical techniques to treat electron and phonon transport are leading to model the physical properties of nano and molecular scale junctions. In this thesis, I use these methods not only to understand the experimental observations by experimental collaborators, but also to develop strategies to design and engineer molecular electronic building blocks, thermoelectric devices and sensors. In this thesis, after a discussion about the theoretical methods used to model electron and phonon transport through the nanoscale junctions, I cover four main results in the areas of molecular sensing, new graphene-based molecular junctions, quantum interference rules and thermoelectricity (or thermal management). I demonstrate the discriminating sensing properties of new bilayer-graphene, sculpturene-based nano-pore devices for DNA sequencing. A unique and novel signal processing method is presented to selectively sense the nucleobases based on direct electrical current. Then I consider a newly developed platform for single-molecule device fabrication based on electro-burnt graphene nano-junctions, which allows three terminal device realization at a single molecule level with gating capability. I provide a fundamental understanding of transport phenomena in these junctions. Furthermore, I discuss our newly developed mid-gap transport theory for single molecules, where in the weak coupling regime and in the vicinity of the middle of the HOMO and LUMO gap, a minimal parameter-free theory of the connectivity dependent transport and quantum interference could be used to model conductance measurements in polycyclic aromatic hydrocarbons. After these discussion of the electronic properties of the junctions, I consider the phonon transport through the nano and molecular scale devices. This allows me to identify strategies for controlling the transmission of phonons from one side of the junction to another for both low-power thermoelectric and thermal management devices.