Mechanically controllable strain junctions: targeting quantum effects and strong plasmonic coupling in ultra-narrow gaps

机械可控应变结：针对超窄间隙中的量子效应和强等离子体耦合

• 批准号: 287911648
• 负责人: Dr. Kai Braun
• 金额: --
• 依托单位: Institut für Physikalische und Theoretische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/287911648?language=en
• 关键词: Mechanically; controllable; strain; junctions; targeting

Within the last decade gap antennas have been widely studied and are commonly used due to the strongly enhanced coupled electrical fields within their gap, which can be spectrally tuned over a wide range. Many emerging nano-photonic technologies depend on the careful control of this plasmonic coupling, including optical nanoantennas for high-sensitivity sensors in chemical and biological applications and improved photovoltaic devices. Typically the distances between the metallic nanostructures range from several tens of nm down to a few nm. Only recently several groups managed to produce and measure sub-nanometer gaps, which show new phenomena such as coherent quantum tunnelling. These effects could become crucial in nanoscale optoelectronics and may pave the way to single molecule opto-electronics.Nevertheless, achieving reproducible and stable experimental conditions with sub-nanometer sized gaps remains a challenging task in high demand. In addition, the methods demonstrated so far are in many cases not suitable for preparing resonant plasmonic coupling with a preselected optical frequency, since their plasmonic properties are not very well-controllable due to a strong dependence on the random preparation processes. In the present work, the approach of using mechanically controllable break junctions (MCBJs) will be revised by developing mechanically controllable strain junctions (MCSJs). MCBJs have shown great performance in measuring tunneling effects and single molecule conductance even at ambient conditions, but unfortunately exhibit poor control of the formed electrode gap geometry itself. The shape of the plasmonic tips in the gap region of a MCSJ is lithographically pre-defined on a pre-stretched substrate, which afterwards will be controllably released to approach the tips.The initial part of this work is dedicated to test measurements on MCBJs. These experiments are used to validate the stretching control setup and establish a link to literature results. The objectives of this project are to develop a well-defined, tunable experimental setup for investigating the interplay between the optical and electronic properties of a nano-gap between metal antennas under wide parameter variation, both for pure gaps and for gaps bridged by molecules, with sub-nanometer control under ambient conditions. With this setup the regime of strong coupling and quantum plasmonics will be addressed. The results from luminescence, electronic transport and Raman studies, all on exactly the same system under variation of antenna geometry, gap size, bias voltage, and molecular bridging will be collected. The project thus aims at gaining new insight into the plasmonic mode distribution, role of the evanescent near-field, electrical biasing, and molecular conductivity in the strong coupling regime.

在过去的十年中，由于间隙内的耦合电场强烈增强，因此可以广泛研究间隙天线，并经常使用。许多新兴的纳米光子技术取决于对这种等离子耦合的仔细控制，包括用于化学和生物学应用中高敏感性传感器的光学纳米annoantennas以及改进的光伏设备。通常，金属纳米结构之间的距离范围从几十nm到几个nm。直到最近，几个小组才能产生和测量亚纳米间隙，这些间隙显示了新现象，例如相干量子隧道。这些效果在纳米级光电学中可能至关重要，并且可能为单分子光电子学铺平道路。不过，实现了可再现和稳定的实验条件，并具有次纳米尺寸的间隙，这在高需求中仍然是一项艰巨的任务。此外，到目前为止所证明的方法在许多情况下不适合以预选的光学频率制备等离子等离子耦合，因为由于其对随机制备过程的强烈依赖性，因此它们的等离子性能不能很好地控制。在目前的工作中，将通过开发机械可控的应变连接（MCSJ）来修改使用机械控制的断裂连接（MCBJ）的方法。 MCBJ即使在环境条件下，MCBJ在测量隧道效应和单分子电导率方面表现出色，但不幸的是，对形成的电极间隙几何本身的控制不良。 MCSJ间隙区域中的等离子尖端的形状是在预伸拉伸的底物上预先定义的，后来将被控制释放以接近尖端。这项工作的初始部分专门用于MCBJS上的测试测量。这些实验用于验证拉伸控制设置并建立与文献结果的链接。该项目的目的是开发一个明确的，可调的实验设置，以研究在较大的参数变化下金属天线之间纳米间隙的光学和电子特性之间的相互作用，包括用于纯间隙，以及在环境条件下与子纳米计的分子桥接的间隙。通过这种设置，将解决强耦合和量子等离子间的策略。发光，电子传输和拉曼研究的结果，所有这些都将收集天线几何形状，间隙尺寸，偏置电压和分子桥接的完全相同系统。因此，该项目旨在获得对等离激元模式分布的新见解，evanevencent近场的作用，电气偏置和在强耦合方案中的分子电导率。