Quantum Transport In Graphene Nanoribbon Decorated With A Phenanthrene Molecule

With development of science and technology,electrical devices need more and more small size,low energy consumption,and the traditional silicon devices can not meet the growing needs of people,so the molecular electronic devices with nano-size have been widely concerned.In the first and second chapters,we expound the development process of the concept and theoretical method of molecular electronics.After that,the structure and properties of Phenanthrene(PHE),an organic molecule modified on the edge of graphene,are introduced.Based on the first principles of ATK,the software is used to model and calculate all PHE modified graphene devices.In Chapter 3,PHE molecules are covalently coupled to the edge of zigzag graphene nanobelts(ZGNR)after dehydrogenation,to form three hybrid structures.The dispersion relation,current voltage characteristic curve,differential conductance,transmission spectrum and molecular projection self consistent Hamiltonian of these PHE / ZGNR hybrid systems are calculated by first principles.The results show that these double electrode devices have negative differential resistance,conductivity enhancement,parity and other properties,and the physical mechanism of the above results is explained in a deep level.In Chapter 4,the quantum transport properties of PHE at the edge of armchair graphene nanoribbons(AGNR)are calculated by the first principles of DFT and NEGR.After coupling PHE,the conductance of AGNR with width of 5 increases,while that of AGNR with width of 6 decreases.The physical mechanism of the increase and decrease of conductance is explained by differential conductance,transmission spectrum and local density of states.Finally,compared with the pristine AGNR,the enhancement of conductivity has nothing to do with the length of the central scattering region.However,with the increase of the length of the scattering region,the system resistance will increase.