Systematical Analysis Of Electronic Transport In Nano-device

Recent advances in the fabrication of nano-devices have raised interest in theoretical research of quantum transport.Since transport property of nano-scale system provide a convenient perspec-tive to probe into the inside of system and a direct link to potential novel nano-device applications.As system information is carried by variety of particles such as electron,phonon,magnon,and spin,among which electron is the most common type.Previous researches mainly focus on the conductance or current in nano-device,but neglect the detailed information such as the transport of each mode.Thus,an accurate and efficient theoretical tool is needed to explore detailed transport information on the nanoscale electronic systems.Based on simple model and present theory,we study Green's function theoty,scattering matrix and Bloch theory.By combining Green's function and Bloch theory,we find an approach named mode-analysis approach,which can be independently used to explore detailed mode information,or can be used to as a tool to expand research of nano-scale system.The main content are as follows:We firstly introduce basic model of quantum transport system,based on which the principles of Bloch theory,scattering matrix and Green's function are expounded.In tight-binding repre-sentation,we find the solution of Bloch eigen-modes in system of periodic structure.Then the derived Bloch matrices are used to describe the propagation process of wave function in system.Some complicated system such as singular coupling matrix and multi-layer structure are deeply discussed so as to sum up the general Bloch theory for transport systems.From analytic continua-tion,the causality of the system is determined,and the advanced and retarded Bloch eigen-modes are derived.By combining Bloch theory and Green's function,terms such as surface Green's function,self-energy,and coupling matrix in Green's function theory can be described with Bloch language.The two approach are proved to be equivalent,which is helpful for us to understand the physical meanings of terms in the two theories.Fisher-Lee relation t=i?L1/2G?R1/2 is a well-established tool to decode the mode information from Green's function and coupling parameters.Using the Bloch eigen-modes of the leads,we show that the ?L/R1/2 term can be defined by the Bloch eigen-mode vectors and the wave velocities which give unambiguous algorithm of ?L/R1/2 in the Fish-Lee relation.With the assistant of Green's function,we simplify the process of solving Bloch eigen-modes.This approach is named mode-analysis approach with which we can avoid complicated mathematical algorithms.Using this approach,we present an accurate and convenient technique to analyze all transport modes and also the dominant channels in an electronic transport system.We study graphene nanoribbon structures to demonstrate the typical application of our technique.Based on some existing graphene FET(GFET)devices,we apply our technique to nano-size GFET and discuss how the voltage of each electrode influence the electronic transport in this device.This work will provide valuable reference to the development of smaller GFET.