Transport Properties Of Graphene Strips With A Nano-electronic Devices

This dissertation gives a comprehensive presentation of investigations on transport properties with nonequilibrium Green's function method combined with density functional theory (NEGF-DFT), as well as its application on graphene nanoribbon based nano-electronic devices. The first chapter de-scribes the application and academic background of graphene nano-devices. The second one gives the detailed formulism and numerical algorithms used in the work, including the definition of the generalized Hamiltonian of an open system, the Green's function based on the generalized Hamiltonian, Landauer-Biitiker equation, and the equations needed to give density of states (DOS) as well as local density of states (LDOS). Contour integral algorithm and the self-consistent loop is also presented at the end of this chapter. Fi-nally, the calculation results of zigzag graphene nanoribbons (ZGNR.) are presented in the third chapter. Further discussions about the relationship between the band structure of leads and the transmission spectrum of the open system is pointed out. In this chapter, we mainly investigate the pos-sible methods that could be applied to control the transport behavior of ZGNRs, applying the narrow 4-ZGNR as an object. The redistribution of HOMO and LUMO molecular orbital induced by external electrical potential is a possible mechanism to control the tunneling current of ZGNR junctions. Particular attention is paid to the structure dependent switching effect of edge-defect ZGNR. junctions. The polarization induced switching effect is sensitive and the on-off ratio of I-V curve of the junction is considerable, which brings about the possibility that edge-defect ZGNRs could be applied as a candidate material in nano-electronic devices.