Single-Molecule Plasmoelectronics

计算机芯片中电子元件的不断小型化最终将导致元件尺寸达到分子级。在这些长度尺度上的传统半导体纳米结构将遭受由于隧道效应而增加的漏电流，以及由于更高的功率密度而增加的热效应。在过去的二十年里，对开发替代方法的需求创造了分子电子学领域，在分子电子学领域中，电子元件是用单分子实现的。使用单个分子的二极管、存储元件和晶体管等典型器件的许多例子已经被证明。其中最重要的功能之一是控制通过具有外部刺激的器件的电流，即门控。已经使用的刺激包括静电和电化学势、温度和光。光是最有吸引力的选择之一，因为它有可能将单分子设备与未来的光电子电路连接起来，有望实现终极速度和小型化。使用等离子体纳米结构可以实现光与纳米级物体的有效耦合，等离子体纳米结构可以聚集和聚焦超过衍射极限的光。与电子设备相结合，人们谈到了等离子体电子学。这种高效的、空间受限的耦合是在100 nm以下的光学栅级分子器件紧密集成的先决条件。这项研究旨在实现单分子等离子体电子器件，其中通过耦合到等离子体纳米结构的单个分子的电流通过外部照明来选通。设想的器件结构将利用贵金属纳米颗粒的等离子体性质，作为单分子结的电极。这项研究将为光电子器件的小型化、集成化和单分子水平的控制开辟新的机遇。研究是跨越物理、化学、分子电子学和等离子体的交叉学科。这反映在研究小组汇集了单分子导体有机合成(Beeby，Durham)、单分子传导测量(Nichols，Higgins，利物浦)和纳米等离子体(Jaeckel，利物浦)方面的专业知识。这种广泛的专业知识将允许系统地改变分子导体的化学性质，并使其与单分子结的等离子体性质相匹配。这将允许详细描述诸如结中的光谱重叠和电子耦合等参数，以及它们与器件中的光学门控效应的关系。单分子方法将消除可以掩盖宏观测量中的重要影响的系综平均效应和使结果解释更加复杂的样品异质性。该项目将提供对等离子体电子单分子结的基本理解，并为未来的设备制定设计规则。这一成果还将在光伏、有机电子学和催化等相关研究领域开辟新的机遇。

Continuing miniaturization of electronic components in computer chips will eventually lead to component sizes on the molecular scale. Conventional semiconductor nanostructures at these length scales will suffer from increased leakage currents due to tunnelling as well as increased thermal effects due to higher power densities. The need for developing alternative approaches has created over the last two decades the field of molecular electronics, in which electronic components are realized using single molecules. Numerous examples of prototypical devices such as diodes, memory elements and transistors employing individual molecules have been demonstrated.One of the most important functions is the control of the current through a device with an external stimulus, i.e. gating. Stimuli which have been employed include electrostatic and electrochemical potentials, temperature, and light. Light is one of the most attractive options since it potentially allows coupling single-molecular devices with future optoelectronic circuitry, holding the promise of ultimate speed and miniaturization. Efficient coupling of light with nanoscale objects can be achieved using plasmonic nanostructures that concentrate and focus light beyond the diffraction limit. In combination with electronic devices one speaks of plasmoelectronics. Such efficient and spatially confined coupling is a pre-requisite for the tight integration of optically gate-able molecular devices on the sub-100 nm scale. The proposed research aims at realizing single-molecular plasmoelectronic devices in which the current through a single molecule coupled to a plasmonic nanostructure is gated by external illumination. The envisaged device structures will take advantage of the plasmonic properties of noble metal nanoparticles that serve as the electrodes of the single-molecule junction. This research will open new opportunities for miniaturization, integration, and control of optoelectronic devices to the single-molecule level.The research is interdisciplinary spanning physics, chemistry, molecular electronics and plasmonics. This is reflected in the research team which brings together expertise in organic synthesis of single-molecular conductors (Beeby, Durham), single-molecule conduction measurements (Nichols, Higgins, Liverpool), and nanoplasmonics (Jaeckel, Liverpool). This broad expertise will allow for a systematic approach varying the chemical nature of the molecular conductor and matching it with the plasmonic properties of the single-molecule junction. This will allow detailed characterization of parameters such as spectral overlap and electronic coupling in the junction and their relation to the optical gating effect in the device. The single-molecule approach will eliminate both ensemble averaging effects which can mask important effects in macroscopic measurements and sample heterogeneity which makes interpretation of results more complex. The project will deliver a fundamental understanding of plasmoelectronic single-molecule junctions and formulate design rules for future devices. The results will also open new opportunities in related research areas such photovoltaics, organic electronics, and catalysis.