B/N掺杂对于石墨烯纳米片电子输运的影响

选用锯齿(zigzag)型石墨烯纳米片为研究对象, Au作为电极, 分子平面与Au的(111)面垂直, 并通过末端S原子化学吸附于金属表面, 构成两种分子器件: 一种是在纳米片的边缘掺杂N(B)原子, 发现电流-电压具有非线性行为, 但是整流系数较小, 特别是掺杂较多时, 整流具有不稳定性; 另一种是用烷链把两个石墨烯片连接, 在烷链附近和石墨烯片的边缘进行N(B)掺杂, 发现在烷链附近掺杂具有较大的整流, 但是掺杂的原子个数和位置会影响整流性能. 研究表明: 整流主要为正负电压下分子能级的移动方向和空间轨道分布不同导致. 部分体系中的负微分电阻现象主要由于偏压导致能级移动和透射峰形态的改变, 并且在某些偏压下主要透射通道被抑制而引起. 关键词： 石墨烯纳米片 电子输运 整流行为 非平衡格林函数方法

The electronic transport properties affected by B/N doping in graphene-based molecular devices

The electron transport properties of the system consisting of the zigzag graphene nanoflake doped with nitrogen and boron atoms connected to two Au electrodes through S-Au bonds are investigated theoretically. The results show that a nanoflake doped with nitrogen and boron atoms at edges has poor rectifying performance. While the system consisting of two pieces of graphene flakes doped by boron and nitrogen atoms, respectively, and linked with an alkane chain, shows good performance. And the significant effects of the doped sites on the current-voltage characteristics are observed. The mechanisms for these phenomena are explained by the different shifts of transmission spectra, the different spatial distributions of the molecular projected self-consistent Hamiltonian eigenstates. The negative differential resistance behavior results from the biase induced shifts of the energy level and change of the resonance transmission spectra, and the suppression of the relevant channels at some bias voltages.
Keywords： graphene nanoflake electronic transport rectifying performance non-equilibrium Green’s function method