Electron transport through extended metal atom chains

通过延长的金属原子链进行电子传输

• 批准号: EP/F019327/2
• 负责人: John McGrady
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF019327%2F2
• 关键词: Electron; transport; through; extended; metal

The dramatic expansion of the electronics industry over the past 40 years has been based on the progressive reduction in size of the silicon-based semiconductor components of integrated circuits. Indeed, Moore anticipated this trend in his much-quoted 1965 paper, where he predicted an approximate 2-fold increase in the performance of such circuits every 12 months ('Moore's law'). The minituarisation of semi-conductor circuits cannot, however, continue indefinitely, and we are rapidly approaching the stage where quantum effects will prevent further dramatic improvements in computer performance using existing technology. As a result, the field of molecular electronics, which seeks to identify and develop much smaller molecular analogues of the transistors that make up integrated circuits, has expanded rapidly over the past few years.At a simplistic level, the key property of any component of an electronic circuit is its ability to control the flow of electric current. As a result, most work has focussed on conjugated carbon-based materials, where the delocalised pi system provides an obvious electron transport pathway. Very recently, however, an alternative strategy based on extended chains of metal atoms surrounded by an insulating sheath of organic material has been developed independently by two experimental groups (Peng, Taipei and Cotton, Texas). The superficial resemblance between these Extended Metal Atom Chains (EMACs) and macroscopic wires is very appealing, but, at a more subtle level, the inate flexibility of the metal-metal bonds that define the core offers a range of possibilities for controlling electron transport.The initial inspiration for this proposal came from our exploration of the electronic structure of a rather simple EMAC, containing a metal core of just three cobalt atoms. The remarkable structural chemistry of this species had been a long-standing mystery: the molecule could apparently exist in at least two distinct forms, whose structures were markedly dependent on temperature. Using density functional theory, we showed that the unique properties of this system arise through a bi-directional redistribution of electron density within the molecule: electrons move in one direction through the sigma framework and in the other through the manifold of delta orbitals in response to subtle changes in temperature. This discovery prompted us to ask a very simple question: if this bi-directional flow of electrons occurs in response to such subtle environmental changes , what might happen if the system is placed under an applied voltage, as it would be in an integrated circuit? The most exciting possibility is that the molecule might act as a molecular rectifier, allowing current to flow more easily in one direction (through the sigma framework, for example) than the other. Rectification of current in junction diodes was perhaps the single most important discovery that led to the development of the transistor in the 1950's, and the discovery of molecular analogues is likely to have a similar impact in the next generation computer architecture. Aviram and Ratner set out the basic features of a molecular rectifier (based on conjugated aromatics) as early as 1974, but the possibility that metal chains may act in a similar way, albeit through a completely different mechanism, has not yet been considered. We aim to use our detailed understanding of the electronic structure of the isolated EMACs as a platform to explore how they behave when placed under an applied voltage. Ultimately, we hope to use the knowledge gained from our theoretical study to construct a rational framework for the future design of components for molecular electronics.

电子工业在过去40年中的急剧扩张是基于集成电路的硅基半导体元件尺寸的逐步减小。事实上，摩尔在他1965年的论文中预测了这一趋势，他预测这种电路的性能每12个月大约增加2倍（“摩尔定律”）。然而，半导体电路的微型化不可能无限期地持续下去，我们正在迅速接近量子效应将阻止使用现有技术的计算机性能进一步显著改善的阶段。因此，分子电子学领域在过去几年里迅速发展，该领域旨在识别和开发构成集成电路的晶体管的更小分子类似物。简单地说，电子电路中任何元件的关键特性都是控制电流流动的能力。因此，大多数工作都集中在共轭碳基材料上，其中离域π系统提供了明显的电子传输途径。然而，最近，两个实验小组（台北的彭和德克萨斯州的科顿）独立开发了一种替代策略，该策略基于由有机材料绝缘鞘包围的金属原子延伸链。这些扩展金属原子链（EMAC）和宏观线之间的表面相似性非常吸引人，但是，在更微妙的水平上，定义核心的金属-金属键的内在灵活性提供了一系列控制电子传输的可能性。这个提议的最初灵感来自于我们对相当简单的EMAC的电子结构的探索，它的金属核只有三个钴原子这个物种的非凡结构化学是一个长期存在的谜团：分子显然可以以至少两种不同的形式存在，其结构明显依赖于温度。使用密度泛函理论，我们表明，该系统的独特性质是通过分子内电子密度的双向重新分布而产生的：电子在一个方向上通过sigma框架移动，而在另一个方向上通过delta轨道的歧管响应于温度的微妙变化。这一发现促使我们提出一个非常简单的问题：如果这种电子的双向流动是为了响应这种微妙的环境变化，那么如果将系统置于外加电压下，就像集成电路中那样，会发生什么？最令人兴奋的可能性是，这种分子可能充当分子整流器，使电流更容易沿一个方向流动（例如，通过sigma框架）。结型二极管中电流的整流可能是导致20世纪50年代晶体管发展的最重要的发现，而分子类似物的发现可能会对下一代计算机体系结构产生类似的影响。Aviram和Ratner早在1974年就提出了分子整流器（基于共轭芳烃）的基本特征，但金属链可能以类似的方式起作用的可能性，尽管是通过完全不同的机制，尚未被考虑。我们的目标是利用我们对隔离EMAC电子结构的详细了解作为平台，探索它们在施加电压时的行为。最终，我们希望利用我们的理论研究所获得的知识，构建一个合理的框架，为未来的分子电子学组件的设计。

项目成果

Can heterometallic 1-dimensional chains support current rectification?

• DOI: 10.1039/c3cc45063e
• 发表时间: 2013-09
• 期刊: Chemical communications
• 影响因子: 4.9
• 作者: Daniel DeBrincat;Oliver Keers;J. McGrady

Influence of Low-Symmetry Distortions on Electron Transport through Metal Atom Chains: When Is a Molecular Wire Really "Broken"?

• DOI: 10.1021/ja2028475
• 发表时间: 2011-08-17
• 期刊: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
• 影响因子: 15
• 作者: Georgiev, Vihar P.;McGrady, John E.
• 通讯作者: McGrady, John E.

Attenuation of Conductance in Cobalt Extended Metal Atom Chains

钴延长金属原子链中的电导衰减

• DOI: 10.1021/jp304807w
• 发表时间: 2012
• 期刊: The Journal of Physical Chemistry C
• 作者: Georgiev V

Periodic trends in electron transport through extended metal atom chains: comparison of Ru3(dpa)4(NCS)2 with its first-row analogues

• DOI: 10.1039/c2sc01024k
• 发表时间: 2012-03
• 期刊: Chemical Science
• 影响因子: 8.4
• 作者: P. Mohan;V. Georgiev;J. McGrady

Redox-Dependent Metal-Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling.

• DOI: 10.1002/chem.201704727
• 发表时间: 2018-04
• 期刊: Chemistry
• 作者: Mohammed Obies;N. Perkins;V. Arcisauskaite;G. Heath;A. Edwards;J. McGrady