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利用自恰tight-binding 理论,对由phenalenyl分子构成的全对称三电极纳米单分子器件的电子传导特性进行了理论研究. 通过改变电极与分子界面上的耦合,得出了分子与原子线电极间耦合强度变化对电子传输的影响. 结果显示电子通过phenalenyl分子器件的概率随着分子与电极的耦合强度变弱而减小. 当耦合强度变大时,不仅电子通过phenalenyl分子器件的概率变大,而且在较宽的能带内电子都可以通过phenalenyl分子. 所得结果还揭示出在特定的能区,对称三电极phenalenyl分子可以构成一个无源正负能量开关器件的新特性. 相似文献
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利用基于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,开展了氧气分子吸附对以石墨烯纳米带为电极的单蒽分子器件自旋极化输运性质的调控物理机理探索研究.计算结果显示,在未吸附氧气分子时,单蒽分子以横向方式连接石墨烯纳米带要比单蒽分子以纵向方式连接石墨烯纳米带具有更优异的自旋过滤效应.当氧气吸附单蒽分子后,两种构型器件的自旋电流都会大幅度降低,但是自旋过滤效应会有所增强.尤其是单蒽分子以横向方式连接石墨烯纳米带的器件在±0.5 V区间始终保持了近100%的自旋过滤效率.通过分析器件的自旋极化输运谱、输运本征态和自旋过滤效率等,详细地解释了氧气分子吸附调控器件的自旋输运性质以及改善器件的自旋过滤行为的物理机理. 相似文献
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在磁电子学领域,自旋极化输运与分子器件的结合是一个热门研究方向.最近,来自美国康奈尔大学的Pasupathy等,采用纳米加工技术,将单个C60分子吸附在一对Ni电极之间,构成了“铁磁电极-C60量子点”器件.量子点的Kondo效应和铁磁性交换耦合,原本是相互排斥的,在Pasupathy的实验中,两者被首次结合在一个器件中并加以观察.研究结果表明,如果器件的质量能够保证两种效应之间的竞争得到有效控制, 相似文献
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在磁电子学领域,自旋极化输运与分子器件的结合是一个热门研究方向.最近,来自美国康奈尔大学的Pasupathy等,采用纳米加工技术,将单个C60分子吸附在一对Ni电极之间,构成了“铁磁电极-C60量子点”器件.量子点的Kondo效应和铁磁性交换耦合,原本是相互排斥的,在Pasupathy的实验中,两者被首次结合在一个器件中并加以观察.研究结果表明,如果器件的质量能够保证两种效应之间的竞争得到有效控制, 相似文献
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分子尺度上的光电相互作用研究可以为发展未来信息和能源技术提供科学基础.扫描隧道显微镜不仅可以用来观察和操纵纳米世界中的原子和分子,而且其高度局域化的隧穿电流还可以被用来激发隧道结中的分子,使之发光,以研究局域场下的分子光电特性.本文综述了中国科学技术大学单分子光电研究组近期在锌酞菁分子电致发光方面取得的科学进展,包括:1)利用有效的电子脱耦合与纳腔等离激元调控技术,实现了隧穿电子激发下的单个锌酞菁分子的电致荧光,并通过发展相关的光子发射统计测量方法,表征了单个分子在隧穿电子激发下的电致荧光具有单光子发射特性;2)发展了具有亚纳米空间分辨的荧光光谱成像技术,实现了对酞菁分子间相干偶极相互作用特征的实空间观察;3)对分子与纳腔等离激元之间的相干耦合作用进行了亚纳米精度的操控,在单分子水平上观察到了法诺共振和兰姆位移效应.这些研究结果不仅为研发基于有机分子的电泵纳米光源与单光子光源等分子光电器件提供了新的思路,而且为在单分子尺度上研究分子光电特性、分子间能量转移以及场与物质之间的相互作用规律等提供了新的表征方法. 相似文献
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Based on the density functional theory and nonequilibrium Green's function methods, we investigate the spin transport properties of the molecular junctions constructed by a homologous series of 3d transition metal(II) salophens (TM-salophens, TM = Co, Fe, Ni and Mn) sandwiched between two gold electrodes. It is found that among the four molecular junctions only Co-salophen junction can act as an efficient spin filter distinctively. The conductance through Co-salophen molecular junction is dominated by spin-down electrons. The mechanism is proposed for these phenomena. 相似文献
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Non-equilibrium Green's functions (NEGF) formalism combined with extended Hückel (EHT) and charging model are used to study
electrical conduction through single-molecule junctions. The analyzed molecular complex is composed of the asymmetric 1,4-Bis((2′-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitrobenzene molecule symmetrically coupled to two gold electrodes. Owing to this
model, the accurate values of the current flowing through such junctions can be obtained by utilizing basic fundamentals and
coherently deriving model parameters. Furthermore, the influence of the charging effect on the transport characteristics is
emphasized. In particular, charging-induced reduction of conductance gap, charging-induced rectification effect and charging-generated
negative value of the second derivative of the current with respect to voltage are observed and examined for the molecular
complex. 相似文献
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运用密度泛函理论对Si60团簇的结构进行几何优化,得到基态结构是一个直径为1.131 nm,平均键长为0.239 nm,分子最低未占据轨道与最高占据轨道能量差即能隙值为0.72 eV,具有C1点群的空心笼状结构.然后把它与两半无限的Au(100)-4×4电极相连构成Au-Si60-Au三明治结构分子结点,运用密度泛函理论结合非平衡格林函数的方法对其电子输运性质进行了第一性原理计算.当两电极的距离为1.74 nm时,分子结点的平衡电导为1.93G0(G0=2e2/h),然后在-2.0—2.0 V的电压范围内,计算了不同电压下的电导与电流,得到其I-V曲线成近线性关系,从分子前线轨道与透射谱分析了Si60分子的电子输运特性,讨论了电荷转移量与电导之间的关系. 相似文献
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结合密度泛函理论和非平衡格林函数方法计算了溶液酸碱性对低聚苯亚乙炔基分子结电输运性质的影响,此低聚苯亚乙炔基分子中两个不同位置的H原子被氨基和羧基取代.通过质子化和去质子化模拟酸性溶液和碱性溶液对分子结构的影响.计算结果表明:中性环境下分子器件具有良好的导电性和微弱的整流效应;碱性溶液中羧基去质子化后,分子器件电流值增长近一倍,但整流效应变化不明显;酸性溶液中氨基质子化后,分子器件正向偏压导电性能略微降低,但整流方向发生明显反转,且与中性环境下的情况相比,整流比提高了近三倍.提出了一种利用化学手段控制分子结导电能力和整流性能的方法. 相似文献
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Carbon nanomaterials (CNMs) are prompting candidates for next generational electronics. In this review we provide a mini overview of recent results on the conductivity of carbon-based molecular junctions obtained from ab-initio methods. CNMs used as nanoelectrodes and molecular materials in molecular junctions are discussed. The functionalities that include the nanomechanically controlled molecular conductance switches, negative differential resistance devices, and electronic rectifiers realized by using CNMs have been demonstrated. 相似文献
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Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions
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A first-principles computational method based on the
hybrid density functional theory is developed to simulate the
electronic transport properties of oligomeric phenylene ethynylene
molecular junctions with H2O molecules accumulated in the
vicinity as recently reported by Na {\it et al.}
[\wx{Nanotechnology}{18} 424001 (2007)]. The numerical results show
that the hydrogen bonds between the oxygen atoms of the oligomeric
phenylene ethynylene molecule and H2O molecules result in the
localisation of the molecular orbitals and lead to the lower
transition peaks. The H2O molecular chains accumulated in the
vicinity of the molecular junction can not only change the
electronic structure of the molecular junctions, but also open
additional electronic transport pathways. The obvious influence of
H2O molecules on the electronic structure of the molecular
junction and its electronic transport properties is thus
demonstrated. 相似文献
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Jing Ning Xin Shen Zi-yong Shen Xing-yu Zhao Shi-min Hou 《Frontiers of Physics in China》2009,4(3):398-402
The conductance of a family of ruthenium-quasi cumulene-ruthenium molecular junctions including different numbers of carbon
atoms, both in even numbers and odd numbers, are investigated using a fully self-consistent ab initio approach which combines
the non-equilibrium Green’s function formalism with density functional theory. Our calculations demonstrate that although
the overall transport properties of the Ru-quasi cumulene-Ru junctions with an even number of carbon atoms are different from
those of the junctions with an odd number of carbon atoms, the difference between the corresponding current-voltage (I–V) characteristics of these molecular junctions declines to lesser than 16% when the voltage goes up. In each group, the molecular
junctions give a large transmission around the Fermi level since the Ru-C π bonds can extend the π conjugation of the carbon chains into the Ru electrodes, and their I–V characteristics are almost linear and independent of the chain length, illustrating potential applications as conducting
molecular wires in future molecular electronic devices and circuits.
相似文献
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利用弹性散射格林函数方法,对4,4-二羧基1,2-二苯乙烯分子的两种异构体与金电极构成的单分子结进行了研究. 研究表明,该类分子是通过末端羧基化学吸附于金表面的,两种分子结电导特性的差异主要是因为分子与电极的相互作用所致. 对每一种分子来说,都存在三种不同的稳定电导值,分别对应着分子末端与金表面的不同接触方式. 分子与金表面的相互作用导致分子结电子结构的变化是其电导差异的主要原因. 理论结果与实验测量结果符合得较好.
关键词:
光致异构体
伏安特性
电子输运
分子电子学 相似文献
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Effect of crystallographic orientations on transport properties of methylthiol-terminated permethyloligosilane molecular junction
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Ming-Lang Wang 《中国物理 B》2022,31(7):77303-077303
The understanding of the influence of electrode characteristics on charge transport is essential in the field of molecular electronics. In this work, we investigate the electronic transport properties of molecular junctions comprising methylthiol-terminated permethyloligosilanes and face-centered crystal Au/Ag electrodes with crystallographic orientations of (111) and (100), based on the ab initio quantum transport simulations. The calculations reveal that the molecular junction conductance is dominated by the electronic coupling between two interfacial metal-S bonding states, which can be tuned by varying the molecular length, metal material of the electrodes, and crystallographic orientation. As the permethyloligosilane backbone elongates, although the σ conjugation increases, the decreasing of coupling induced by the increasing number of central Si atoms reduces the junction conductance. The molecular junction conductance of methylthiol-terminated permethyloligosilanes with Au electrodes is higher than that with Ag electrodes with a crystallographic orientation of (111). However, the conductance trend is reversed when the electrode crystallographic orientation varies from (111) to (100), which can be ascribed to the reversal of interfacial coupling between two metal-S interfacial states. These findings are conducive to elucidating the mechanism of molecular junctions and improving the transport properties of molecular devices by adjusting the electrode characteristics. 相似文献