Study On Electron Transport Properties Of Graphene Nanoribbons Based On Defect Structure

With the continuous development of microelectronics,the use of molecular materials to construct electronic devices with logic functions and computational functions is expected to break through the limitations of traditional silicon devices and become the most likely development trend of microelectronics.In recent years,the majority of scholars have used extensive experimental research on organic electronics by using organic molecular beam epitaxy(OMBE)and other experimental techniques,and found that the molecules have important electrical properties such as rectification effect,switching effect,and negative differential resistance effect.The conclusion provides a solid theoretical basis for the realization of molecular device functionalization.Since its discovery,graphene has been designed and measured by scholars as an excellent electrode material for molecular devices.It has been concluded that the properties of graphene can be adjusted by chemical modification or introduction of doping and defects.Here,the zigzag graphene nanoribbons(ten zigzag-type carbon chains)with a width of 10 are studied.The two-electrode model is established by using four-atom,six-atom edge diamonds and five-atom and six-atom edge squares as defect structures.The whole system is divided into three parts: the left and right half-infinite electrode and the central scattering region.All the band boundary carbon atoms are saturated with hydrogen atoms to ensure the perfect structure and electron stability.The first-principles calculation theory combined with density functional and non-equilibrium Green's function is used to systematically analyze the effects of different shapes(diamonds and squares)and defects of different side lengths on the electrical transport properties of graphene nanoribbons.And the main influencing factors.Based on the conclusions,the influence of the number of edge atoms in the defect structure on the electrical transport properties of graphene nanoribbons is further studied.The results show that the defects have a significant modulation effect on the electrical transport properties of graphene nanoribbons.This paper mainly includes the following five chapters:The first chapter is the introduction part,which mainly introduces the structural characteristics and physical and chemical properties of graphene and its nanoribbons,the generation and classification of defect structures,the research background of molecular electronics and the experimental and theoretical research progress of molecular devices.Finally,the main research contents,purpose and significance of this thesis are given.The second chapter is the software description part of the relevant calculation theory and research.It explains in detail the density-functional theory for electronic structure calculation,the non-equilibrium Green's function method for the calculation of the transport characteristics of molecular devices.At the same time,the first principle calculation theory of the combination of the two is introduced,and several core softwares designed for the whole research are given.In the third chapter,zGNRs with width 10 is used as the electrode of the molecular device.Two two-electrode models are constructed by cutting out the four-atom edge diamond and the five-atom edge square in the central region.The sawtooth with different shape defect structures is systematically studied.The effect of the electrical transport properties of graphene nanoribbons.The results show that the existence of defect structure has a significant effect on the electrical transport properties of sawtooth graphene nanoribbons: the current of perfect graphene nanoribbons at low bias is higher than that of graphene nanoribbons with defective structures.The graphene nanoribbons with defective structures at high bias have higher currents than the perfect graphene nanoribbons.At the same time,the graphene nanoribbons with diamond-shaped defects at the edge of the four atoms show a significant negative differential resistance effect in the range of 1.0V to 1.5V.In the fourth chapter,zGNRs with a width of 10 are also used as the electrodes of the molecular device.Two two-electrode models are constructed by further cutting out the fiveatom edge diamond and the six-atom edge square in the central region,and respectively study the diamond defect and the square defect.The effect of the number of edge atoms on the transport properties of graphene nanoribbons.The results show that when the shape of the defect is a diamond,the more the number of edge atoms,the larger the current passing through the system,and when the shape of the defect is square,the more the number of edge atoms,the smaller the current passing through the system.The fifth chapter summarizes the work carried out in the full text and looks forward to the development of molecular devices.Figure 20,reference 88.