Noise and High Frequency Properties of Single-Molecule Transistors

*非技术摘要*晶体管是信息时代的支柱。在过去的60年里，晶体管已经从几厘米减少到几十纳米，现在每个器件的直径都比人类头发的直径小1000多倍。随着尺寸的进一步缩小，量子效应在决定器件性能方面变得至关重要。与此同时，获取有关设备的详细几何形状和材料质量的信息变得越来越困难。在过去的十年中，随着单分子晶体管(SMT)的发展，这种规模化的极限已经达到了极限，其中电流的关键通道是尺寸为1-2 nm的小分子。这些设备是在纳米尺度上研究传导物理的极佳工具，包括耗散的起源和电子-电子相互作用的重要性。该奖项支持一个项目，其目标是将SMT研究扩展到电导以外的领域，以包括电噪声的测量。以流经该器件的电流波动形式的噪声预计将提供有关SMT内的振动和磁过程的有价值的信息。两名研究生将接受最先进的纳米制造方法培训，并将使用低频和高频技术在不同条件下测量SMT中的噪音，从而为他们未来的学术或工业职业做好准备。如果成功，研究结果将为与未来技术相关的物理学提供新的见解，而工作本身将为进一步的新测量打开大门，包括探测和操纵单电子自旋。技术摘要单分子晶体管(SMTs)是近十年来发展起来的，是在纳米尺度上研究导电物理的优秀工具。SMT是高度量子力学系统，其中电子-电子、电子-振动和基于自旋的相互作用都可以很强。理解这种结构的一个长期挑战是通过电子传导的直流表征可获得的信息有限。对传导和散粒噪声的高频测量可以更深入地了解电子振动和强关联效应的作用。尤其是散粒噪声提供了有关电子隧穿事件之间的相关性的信息。该奖项支持一个项目，该项目使用低频和高频方法在各种条件下测量SMT中的散粒噪声。在含有未配对电子的SMT中，散粒噪声将被用来检验理论预测，即当电子通过近藤过程发生输运时，电子的有效电荷被修正为分数。这些测量结果将为高频射频SMT的最终发展奠定基础。以及可能的单分子电子自旋共振。该计划将为两名纳米科学制造和测量技术的研究生提供最先进的培训，从而为他们未来在学术或工业研究中的职业生涯做好准备。

****NON-TECHNICAL ABSTRACT****The transistor is the underpinning of the Information Age. Over the last sixty years, the transistor has been reduced from several centimeters to a few tens of nanometers, with each device now more than 1000 times smaller than the diameter of a human hair. As sizes are reduced further, quantum effects become critically important in determining device properties. At the same time, it becomes increasingly difficult to acquire information about the detailed geometry and material quality of the devices. In the last decade the ultimate limit of this scaling has been reached with the development of single-molecule transistors (SMTs), where the critical channel for current is a small molecule 1-2 nm in size. These devices are excellent tools for examining the physics of conduction at the nanoscale, including the origins of dissipation and the importance of electron-electron interactions. This award supports a project with the goal of extending SMT studies beyond electrical conduction to include measurements of electrical noise. Noise, in the form of fluctuations in the current through the device, is predicted to provide valuable information about both vibrational and magnetic processes within SMTs. Two graduate students will be trained in state-of-the-art nanofabrication methods and will use both low- and high-frequency techniques to measure the noise in SMTs under various conditions, thus preparing them for future academic or industrial careers. If successful the research results will provide new insights into the physics relevant to future technologies, while the work itself will open the door to further new measurements, including the detection and manipulation of single electron spins. ****TECHNICAL ABSTRACT****Single-molecule transistors (SMTs) have been developed over the last decade, and have been outstanding tools for examining the physics of conduction at the nanometer scale. SMTs are highly quantum mechanical systems where electron-electron, electron-vibrational, and spin-based interactions can all be strong. One persistent challenge in understanding such structures is the limited information available through DC characterization of electronic conduction. Higher frequency measurements of conduction as well as shot noise can provide much deeper insight into the roles of electron-vibrational and strong correlation effects. Shot noise in particular gives information about the correlations between electron tunneling events. This award supports a project to use both low- and high-frequency methods to measure shot noise in SMTs under various conditions. In SMTs containing unpaired electrons, shot noise will be used to test the theoretical prediction that the effective charge of the electron is modified to a fractional value when transport takes place via the Kondo process. These measurements will lay the groundwork for the eventual development of high frequency ?RF-SMTs? and possible single-molecule electron spin resonance. This program will provide state-of-the-art training of two graduate students in nanoscale science fabrication and measurement techniques thereby preparing them for future careers in academic or industrial research.