The Study On Devices And Transport Properties Of P-AP Implanted Graphene Nanoribbons

In this thesis,electron doping and hole doping are studied by density functional theory combined with non-equilibrium Green's function.The effect of electron doping on the properties of graphene nanoribbons was studied by using sp~3-N as an example.The effect of hole doping on the graphene nanobelts of armchair was studied by taking B-doping as an example.Recently,the covalent functionalization of graphene has evolved from the formation of sp~3 hybrid carbon atoms(sp~3-C)at anchor sites to the formation of sp~3hybrid nitrogen(sp~3-N)at anchor sites.Here,we systematically investigated the transport properties and electronic structures of graphene nanoribbons(GNRs)functionalized by covalently bonding of p-aminophenol(p-AP)molecule.And we also explored the feasibility of using p-AP functionalized graphene nanoribbons to fabricate molecular devices.We studied the effects of p-AP molecules on armchair graphene nanoribbons(AGNRs)and zigzag graphene nanoribbons(ZGNRs).The study found that the p-AP molecule did not change the ground state of AGNRs and ZGNRs.By analyzing the electronic structure of the three configurations of p-AP-AGNRs,we found that the electronic properties of AGNRs are almost unaffected by p-AP molecules,so it is expected that the transport current is extremely weak.The transport calculation results for p-AP-ZGNR show that the p-AP-ZGNR system exhibits a strong current polarization effect(100%)and significant spin splitting under low bias voltage.In order to investigate the mechanism of p-AP-ZGNR high current polarization,we constructed several sub-structure doping models of p-AP molecules and N-doping models,and calculated their band structure,projected density of states(PDOS).and molecular orbital maps,etc.From the above research results,the spin filtering(ie,strong current polarization)performance of p-AP-ZGNR is insensitive to the substructure of p-AP molecules,and the formed sp~3-N plays a crucial role in determining the electronic structure and transport of the system.Our findings reveal the importance of sp~3-N and suggest a new mechanism for realizing high-performance spin-filter devices with functionalized graphene.We studied the effect of boron atom(B)doping on the electronic properties of7-AGNRs.We calculated the ground state,energy band and PDOS of seven length B-doped 7-AGNRs.It is found that B-doping changes the ground state of the 7-AGNRs system and causes a significant splitting of their energy bands.The lower the concentration,the greater the degree of band splitting.Unlike previous studies(B-7-AGNRs exhibit energy splitting mainly from their interaction with the substrate),our results show that the energy splitting is the eigenstate of the B-7-AGNRs system.Our research is important for modulating the electronic properties of AGNRs and expanding their applications in molecular electronics.