By applying the nonequilibrium Green function method, we have theoretically investigated the quantum transport properties of armchair and zigzag graphene nanoribbons (GNRs), with defects (vacancies) appearing at the edges or in the inner part. Effects of the defects on the electronic conductance and local density of states are comprehensively studied. It is found that both edge and inner defects reduce the electronic conductance in general, while in detail they have different effects on the transport properties for different combinations of defect location and GNR edge type. Under the same theoretical framework, we have also studied the effects of dephasing scattering processes in the GNRs, employing two specific choices of self-energy that provide momentum-conserving or momentum-relaxing dephasing processes. The momentum-relaxing dephasing processes not only relax momentum but also add an additional resistance to the channel, while the momentum- conserving dephasing processes only break the phase and have much less effect on the resistance. It is found that the transport properties of metallic zigzag GNRs are much more strongly modified by the dephasing scattering processes than are those of semiconducting armchair GNRs.

通过应用非平衡格林函数方法，我们从理论上研究了扶手椅形和曲折形石墨烯纳米带（GNR）的量子传输性质，在边缘或内部出现了缺陷（空位）。全面研究了缺陷对电子电导率和态局部密度的影响。发现边缘缺陷和内部缺陷通常都会降低电子电导率，而对于缺陷位置和GNR边缘类型的不同组合，它们对传输特性的影响不同。在相同的理论框架下，我们还研究了GNR中相移过程的影响，采用两种特定的自能选择，它们提供了动量守恒或动量松弛相移过程。减小动量的移相过程不仅使动量松弛，还给通道增加了额外的阻力，而保持动量的相移过程仅破坏了相位并且对阻力的影响小得多。已发现，金属之字形GNR的传输特性比相变扶手椅GNR的迁移特性受到相移散射过程的影响更大。