石墨烯纳米片电子结构和量子输运特性第一原理研究

First-principles study on electronic structure and quantum transport property of graphene nanoplatelets

用基于密度泛函理论的原子紧束缚方法计算研究单层石墨烯纳米圆片和纳米带的电子结构,并结合第一原理和非平衡函数法计算量子输运特性.通过电子能态和轨道密度分布研究纳米碳原子层的电子成键状态,结合电子透射谱、电导和电子势分布分析电子散射与输运机制.石墨烯纳米带和纳米圆片分别呈现金属和半导体的能带特征,片层边缘上电极化分别沿垂直和切向方向,电子电导出现较大的差异,来源于石墨烯纳米圆片边缘的突出碳原子环对电子的强散射.石墨烯纳米带的电子透射谱表现为近似台阶式变化并在费米能级处存在弹道电导峰,而石墨烯纳米圆片的电子能带和透射谱在费米能级处开口并且因量子限制作用呈现更加离散的多条高态密度窄能带和尖锐谱峰.

The electronic structures and quantum transport properties of graphene circle nanoplatelet and nanoribbon are theoretically studied by density-functional-based tight binding method combined with non-equilibrium Green's function.The electron eigen energy and orbital spacial distribution are analyzed to investigate the electronic bonding states of carbon atomic layer,and the transmission spectrum and electrical conductivity are calculated to explore electron scattering and transport mechanism based on the electronic potential field.The graphene nanoribbon and circle nanoplatelet represent metallic and semiconductor characteristics of electron energy bands respectively with normal and tangential electric polarizations at carbon layer edge.Graphene circle nanoplatelet exhibits remarkably smaller electrical conductivity compared with graphene nanoribbon,due to the substantial electron scattering by unsaturated chemical bonds of carbon atoms at the edge of circle nanoplatelet.Graphene nanoribbon presents step like transmission spectrum and characteristic impact peak at Fermi level,while the electron energy states and transmission function of circle nanoplatelet are respectively discrete to higher density energy bands and sharper spectral peaks resulting from specific quantum confinement.