Theoretical Study On The Electrical Performance Of Graphene Nanomaterial Influened By Point Defects

Graphene is a hexagonal lattice which consists of single atomic layer of sp2 hybridized carbon atoms. With this special structure,it has good electronic transport properties. The defects and impurities, which can easily be introduced in while producting, extended various profemences and also make further impact on to be the most promising candidate for the ultimate utilization of the next generation nanodevices.In particular, graphene can be lithographically patterned into quasi one-dimensional graphene nanoribbons (GNRs) and energetic particle irradiation technique demonstrated recently has allowed select modification on atomic structure of nanomaterials by introducing point defects. The advances on the experiments provide the fundament on the preparation of graphene nano electronic devices. This paper mainly studys the point defect in GNRs on the influence of the electrical performance and transport properties. The main contents are outlined as follows:(1) Using the first principles calculations.we have studied the effects of atomic edge arrangement on the electronic transport properties of zigzag graphene nanoribbons. It is found that these two defective edge structures affect effectively the high stable nanostructure configuration and give rise to pronounced modifications on electronic bands, leading to the shift of Fermi level as well as the occurrence of resonant energies. Both of these two atomic reconstructions would limit the electron transport around the Fermi level, and result in the complete resonant backscattering taking place at different locations. The suppression of conductance is not only related with increasing defect size, but more sensitive to the distribution of defect state, and the modifications on the electronic bands that are influenced by the edge reconstructions.(2) Using the first principles calculations associated with nonequilibrium Green’s function, we studied the electronic structures and quantum transport properties of defective armchair graphene nanoribbons (AGNRs) in the presence of divacancy defects. The various defects are introduced in the pristine AGNRs with 156 atoms. The results show that the presence of divacancy defect gives rise to significant impacts on the band structure and electronic transport properties of AGNRs, leading to the shift of Fermi level. The triple pentagon-triple heptagon (555-777) defect in the defective AGNRs has lower transformation energy and more favorable than the pentagon-octagon-pentagon (5-8-5) defect. It is anticipated that defective AGNRs can exhibit large range variations in transport behaviors, which are strongly dependent on the distributions of the divacancv defect.(3) Using the first principles calculations, we have studied the atomic and electronic structures of Co atoms incorporated in GNR with armchair-shaped edges. The Co atom is embedded in the divacancy defects of AGNRs, and the pristine AGNRs has 104 atoms.The differences between the sites of Co atom and the configuration of the edge C atoms are used to study the stability and electronic structures. The calculation results show that doping with Co atom can induce magnetic in AGNRs. and gives rise to significant impacts on the electronic structure. This leads to the shift of Fermi level. The configurations of spin polarization at the edge of C atoms have influence the stability of structure. Compared to other configurations, the ferromagnetism (FM) coupled is more stable. The stability and electronic structures are strongly dependent on the doping sites and the edge configuration.