Theoretical Study On The Electronic Properties And Magnetic Properties Of Graphene

Graphene, the single-layer hexagonal carbon network of carbon atoms with sp2 hybridization, has attracted great attention due to its exceptional physical and chemical properties. However, two crucial issue regarding the application in electronics and spintronics, a band gap with big on/off ratio and magnetic moment, has become the heat subject of theoretical and experimental researchers,so tuning the electronic and magnetic properties of graphene is the key step to improve its performance.Using first principles calculations, we systematically investigated the structural, electronic and magnetic properties of half-sandwiched organo-ligand (OL)-transition metal(TM) functionalized single-layer graphene (SLG) with different arrangement patterns. Most stable structures have the TM atoms sitting on the hollow site of hexagons of graphene, few structures are favored to have TM atoms on top sites. On one hand, all the half-sandwiched OLTMn- and [TMC4H2]?>-/[TMC6H2]oo- ligands can covalently bonded with graphene with high chemical stability. On the other hand, most OLTM?@SLG are ferromagnetic with the largest magnetic moment of 2.96 ub for Cr3Ant@G77. In contrast, ferri-ferromagnetic properties are found for Fe2Np@G77 and Fe3Ant@G77 and antiferromagnetic properties are found for Ti3Ant@G77. Besides, varies electronic properties are found. All the TMBz@G33 and TMBz@G33 are semiconductors, particularly, the band gaps of CrBz@G33 and MnBz@G33 are rather large (>leV). Differently, the band gaps of TM2Np@G77 and TM3Ant@G77, which band gaps are largely reduced due to the increase of coverage concentrations of TM atoms. Moreover, robust magnetic properties are found for the one dimensional infinite molecule wires functionalized graphene, [TMC4H2]n@G and [TMC6H2]@G, which the magnetic moment of [MnC4H2]oo@G and [FeC6H2]@G per unit cell is up to 2.36 ub and 4.43 (ib. Besides, most one dimensional molecular wires adsorpted graphene are metals, except [MnC4H2]oo@G is semiconductor with a band gap of 0.20 eV.Using first principles calculations, we systematically investigated the electronic and magnetic properties of half-sandwiched cyclopentadienyl-ligand-transition metal(TMCp) functionalized single-layer graphene (SLG), (FeCp)n@SLGs, (n=1,2) with different adsorption sites and adsorption densities. The calculation results show that the (FeCp)?@SLGs are chemically stable based on the covalent d-π interaction between TMCp ligand and graphene except FeCp@G44, FeCp2-B@G44-D5,Fe2Cp2@G44-B2-D5, all the other (FeCp)n@SLGs are ferromagnetic, which the magnetic moments of Fe2Cp2@G33-D1, Fe2Cp2@G33-D2 and Fe2Cp2@G33-D3 are 2.00 μB, 1.43 μB and 1.26 μB, respectively. For the 3×3 graphene supercell, all the (FeCp)n@G33S are semiconductors with the energy gaps of FeCp@G33, Fe2Cp2@G33-D1, Fe2Cp2@G33-D2 and Fe2Cp2@G33-D3s are 1.03 eV, 0.55 eV, 0.14 eV and 1.13 eV, respectively. Different electronic properties are found for 4×4 supercell, the electronic properties of which are metallic with an exception of semiconducting Fe2Cp2@G44-B2-D1. Interestingly,the gap at the dirac point of Fe2Cp2@G44-S1,Fe2Cp2@G44-S2, Fe2Cp2@G44-D3 and Fe2Cp2@G44-D5, Fe2Cp2@G44-B2-D5 are largely opened with the gaps of 0.16 eV, 0.09 eV, 0.12 eV, 0.25 eV, 0.36 eV, respectively. Substituting the Fe with Ni can help enhance the magnetic moments, which the magnetic moments of Ni2Cp2@G44-S1, Ni2Cp2@G44-D5, Co2Cp2@G44-S1 and Co2Cp2@G44-D1 are as large as 2.00 μB, 2.00 μB, 3.48 μB and 3.37 μB,respectively. Besides, NiCp@G44, Ni2Cp2@G44-S1 and Ni2Cp2@G44-D5 are semiconductors with energy gaps of 0.17 eV, 0.13 eV and 0.29 eV, respectively. Our finding show the functionalization of graphene with TMCp-ligands are effectively tune their electronic and magnetic properteis, which can be regarded as promising candidates for graphene-based nanoelectronic devices.The structural, electronic and magnetic properties of transition metal intercalated bilayer graphene, [GTMG]x:ys, x,y is integer, TM=Ti, Cr, Mn, Fe, with different intercalation ratios of TM atoms and intercalation patterns, are systematically studied by density functional theory calculations. Except [GCrG]1:9 and [GMnG]1:9, all the other studied systems are found to be thermodynamically stable with large binding energies (>0.80 eV per TM atom), due to the charges transferring from TM atoms to two-side graphene layers. Most studied systems are ferromagnetic, of which, [GFeG]1:6 has the largest magnetic moment of 7.02 μB. In contrast, two systems of [GCrG]1:8 and [GFeG]1:8 are ferrimagnetic and eight other intercalated structures are nonmagnetic. Interestingly, six intercalation structures of [GTMG]1:18, [GTMG]1:9 and [GTMG]1:6 for TM=Ti, Mn, are semiconductors with the gaps of [GTMG]1:18 are 0.14 eV/0.82 eV, 0.41 eV/0.67 eV, and 0.09 eV/0.06 eV, respectively. By comparison of the effect of intercalation patterns to [GTMG]1:6s at same intercalation ratios, the electronic and magnetic properties of [GTMG]x:ys are found to be sensitive to the TM patterns. For thus, intercalating TM atoms into BLGs are an effective method to tune the electronic and magnetic properties of graphene, and the promising way to design the electronic/spintronic devices are provided.