Effect of the Electrodynamic Environment on Electrical Transport in Nanoscale Structures

电动力环境对纳米结构电传输的影响

• 批准号: 9974365
• 负责人: Alexander Rimberg
• 金额: --
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9974365&HistoricalAwards=false
• 关键词: Effect; Electrodynamic; Environment; Electrical; Transport

9974365RimbergThis project focuses on the investigation of the tunneling process in the presence of a tunable source of radiation. In many nanoscale systems, quantum mechanical tunneling is a fundamentally important process in electrical transport. In condensed matter systems, when considering tunneling attention must be paid not only to the electrons (or other particles) which are themselves tunneling, but also the electromagnetic environment to which they are coupled. In many cases the environment is fixed and not well characterized. In this project a model system consisting of a tunneling structure coupled to a tunable environment has been fabricated. The system consists of an Al/AlOx single-electron transistor (SET) coupled to a quantum dot in a GaAs/AlGaAs heterostructure. The Al/AlOx tunnel junctions form nearly ideal tunneling elements due to their high barriers and lack of defects. The quantum dot forms an extremely flexible environment, since its impedance and energy level structure are tunable over a physically interesting range. By measuring the dc I-V characteristics of the SET as the degree of confinement of the quantum dot is varied, one is able to observe how changes in the environment affect transport through the SET. Furthermore, since the SET I-V characteristics are naturally sensitive to the impedance of the environment and to frequencies eV/h where V is the applied voltage, one may also obtain information about the impedance of the dot at frequencies in the gigahertz range. The research in this project will also serve as an opportunity for students, both graduate and undergraduate, as well as post doctoral research associates to acquire state-of-the-art experimental skills in an area of great technological importance during the next few decades of the 21st Century.%%% In many very small physical systems (ones which measure only a few tens of billionths of a meter on a side), electrons facing a barrier can "tunnel" through the barrier instead of going over it. This kind of process is the dominant form of electrical conduction in many tiny structures. The environment surrounding an electron, including the presence of other electrons or of vibrations, can affect its ability to tunnel. In many cases, however, it is unclear what in the environment is affecting the tunneling, and it is usually impossible to change it. This research proposes to use two specialized devices to approach this problem. One, known as a single electron transistor, allows great control over tunneling; in fact electrons in this device can be used to tunnel one at a time. The second device, known as a quantum dot, consists of a small number (only a few hundred) of electrons confined in a very small area by energy barriers. By controlling the height of the barriers it is possible to control how easy or difficult it is for electrons to enter or leave the dot. This variability will allow the dot to serve as an artificial environment that is well understood and tunable. By fabricating the single electron transistor very close to the dot, one is able to observe how changes in the dot affect the tunneling in the transistor. The goal of this research is then to obtain a clearer understanding of how electrical conduction works in extremely small structures and thereby guide further advances in the technological realization of quantum structures in subnano-technology. Undergraduate and graduate students, as well as post doctoral research associates will participate in this research. They will thereby acquire state-of -the-art skills that will prepare them for employment in forefront areas of science and technology during the 21st Century.

9974365 Rimberg这个项目的重点是在一个可调的辐射源存在的隧道过程的调查。在许多纳米系统中，量子力学隧穿是电输运中的一个基本重要过程。 在凝聚态系统中，当考虑隧穿时，不仅要注意电子（或其他粒子）本身的隧穿，还要注意它们所耦合的电磁环境。 在许多情况下，环境是固定的，没有很好的特点。 在这个项目中，一个模型系统组成的隧道结构耦合到一个可调的环境已经制造。 该系统由Al/AlOx单电子晶体管（SET）耦合到GaAs/AlGaAs异质结中的量子点组成。 Al/AlOx隧道结由于其高势垒和缺乏缺陷而形成接近理想的隧穿元件。量子点形成了一个极其灵活的环境，因为它的阻抗和能级结构可以在物理上有趣的范围内调节。 通过测量SET的直流I-V特性，随着量子点的限制程度的变化，人们能够观察到环境的变化如何影响通过SET的传输。 此外，由于SET I-V特性对环境的阻抗和频率eV/h（其中V是所施加的电压）自然敏感，因此还可以获得关于千兆赫范围内的频率处的点的阻抗的信息。 该项目的研究也将为研究生和本科生以及博士后研究人员提供一个机会，使他们在21世纪世纪的未来几十年里，在一个具有重要技术意义的领域获得最先进的实验技能。在许多非常小的物理系统中（边长只有几十亿分之一米的系统），面对势垒的电子可以“隧穿”势垒，而不是越过它。这种过程是许多微小结构中导电的主要形式。 电子周围的环境，包括其他电子或振动的存在，会影响其隧穿能力。 然而，在许多情况下，不清楚环境中的什么影响了隧道效应，并且通常不可能改变它。本研究提出使用两种专门的设备来解决这个问题。 其中一种称为单电子晶体管，可以很好地控制隧穿;事实上，这种器件中的电子可以一次只隧穿一个。 第二种装置称为量子点，由少量（只有几百个）电子组成，这些电子被能量势垒限制在一个非常小的区域内。 通过控制势垒的高度，可以控制电子进入或离开点的难易程度。这种可变性将允许点作为一个人工环境，这是很好地理解和可调。 通过制造非常靠近点的单电子晶体管，人们能够观察到点的变化如何影响晶体管中的隧穿。 这项研究的目标是更清楚地了解导电如何在极小的结构中工作，从而指导亚纳米技术中量子结构的技术实现的进一步进展。 本科生和研究生，以及博士后研究助理将参与这项研究。 他们将因此获得国家的最先进的技能，将为他们准备就业的前沿领域的科学和技术在21世纪世纪。