摘要:
运用第一性原理密度泛函理论(DFT)和非平衡格林函数(NEGF)方法,研究了[111]Au纳米线与1,4-二硫苯酚(DTB)构成的分子结的电子输运性质.构建并优化不同的Au-DTB接触构型,计算发现：尖端顶位构型最利于电流输运；非对称构型大多具有很好的整流特性(最大整流比为25.6)；部分结构出现双重负微分电阻(NDR)效应.分析表明,整流效应主要源于非对称接触构型两端S-Au键的稳定性差别；尖端金原子与硫原子的耦合能级中,近费米面的能级对低压区电子传输起主要作用；电压增大,离费米面较远的能级对输运起主导作用, DTB的本征能级也逐渐参与,这一转变致使电流出现两峰一谷的双重NDR效应.
Abstract:
Electron transport properties of molecular junctions formed by 1, 4-dithiolbenzene(DTB) coupled to [1,1,1] Au nanowires are investigated by using the method of non-equilibrium Green’s functions based on first-principle density functional theory. Different S-Au contact configurations are constructed and optimized. The junction with tip-type Au electrode top binding to a thio (S) atom is illustrated by the best configuration for electron transport. Juntions with asymmetric electrode-DTB contact show excellent rectifying performance (the largest rectification ratio being 25.6). Other junctions display negative differential resistance (NDR) effect twice. Analysis shows that the rectifying effect may originate from the difference between the stabilities of S-Au contact modes at both sides. Molecular orbitals including the tip Au atoms are calculated. In low bias region, the orbitals near the Fermi energy dominate the electrons transmission;while, as the bias increases, those apart from the Fermi energy contribute to the transport, along with the DTB eigen-level. During the whole process, the locations and amplitude of transmission vary with bias voltage and I/V curves show two peaks, resulting in twice-NDR effect.
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