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中国物理学会期刊

4, 4'-(芘–1, 6-二基)二苯胺分子器件的大峰谷比负微分电阻效应实现与调控

Implementation and regulation of large peak-to-valley ratio negative differential resistance effect in PDE molecular junction

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  • 负微分电阻器件, 因其在高速开关、存储及多值逻辑电路中的应用潜力而受到广泛关注. 采用密度泛函理论结合非平衡格林函数的第一性原理计算方法, 研究了4, 4'-(芘-1, 6-二基)二苯胺(PDE)分子器件的电子输运性质, 探索电极材料与锚定基团对负微分电阻效应的调控机制. 研究结果表明: 采用金电极的PDE分子器件呈现单调递增的电流-电压特性, 而采用锯齿型石墨烯纳米带电极的PDE分子器件呈现显著的低偏压负微分电阻效应, 其峰谷电流比可高达3.9×103. 此外, 酰胺锚定基团增强分子与电极的π共轭界面耦合, 从而产生高电流密度. 与之相反, 胺基锚定基团引发分子与电极耦合界面的相消干涉, 显著降低器件的电导. 本工作为高性能负微分电阻器件的开发提供了有价值的理论基础和设计策略.

     

    Developing negative differential resistance (NDR) devices that simultaneously exhibit high conductance and a large peak-to-valley current ratio (PVCR) remains a critical challenge for the realization of molecular-scale logic circuits. The electronic transport properties of 4,4'-(pyrene-1,6-diylbis(ethyne-2,1-diyl)) dianiline (PDE) molecular devices were studied using density functional theory combined with first-principles calculations using non-equilibrium Green’s functions, exploring the regulatory mechanism of electrode materials and anchoring groups on NDR effects. We first fully optimized the geometric structure of isolated molecules and electrode cells, with the convergence criterion for the residual force on each atom set to less than 0.02 eV/Å. Exchange and correlations were described by the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). The research results indicate that PDE molecular devices using gold electrodes have a continuous and high density of states, and strong hybridization with molecular orbitals leads to broadening of the transport peak, resulting in only monotonically increasing current-voltage characteristics. Due to the low density of states near the Fermi level, PDE molecular devices using zigzag graphene nanoribbon (ZGNR) electrodes do not induce hybridization or broadening of molecular orbitals, maintaining a sharp resonance state and achieving significant NDR effects. Changes in interface coupling caused by anchoring groups can regulate the alignment relationship between frontier molecular orbitals and the electrode Fermi level, playing a decisive role in the NDR effect. The amide group forms strong π-π conjugated coupling with the molecular skeleton and the ZGNR electrode through carbonyl groups, constructing efficient and continuous electron transport channels. In contrast, the amino anchoring group triggers destructive interference at the coupling interface between the molecule and the electrode, significantly reducing the device conductivity and resulting in substantial attenuation of the peak current. These findings deepen our understanding of the quantum transport mechanism at carbon-based molecular interfaces and provide clear theoretical guidance and material design paradigms for the future development of low-power, high-performance molecular switches, logic gates, and high-frequency oscillators.

     

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