Scanned Probe Microscopy using Single-Electron Device Arrays

使用单电子器件阵列的扫描探针显微镜

• 批准号: 1509087
• 负责人: Gregory Snider
• 金额: $ 38万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1509087&HistoricalAwards=false
• 关键词: Scanned; Probe; Microscopy; using; Single

This project will use ultra-sensitive charge detectors coupled to a scanning needle, similar to an Atomic Force Microscope, to make nanoscale-resolution maps of the electrical potential of a surface of solid or soft materials. A novel sensor, based on high-speed version of the most sensitive charge detector, single-electron transistor (SET), will be used. This sensor employs arrays of SETs and radio-frequency reflectometry to give information on fast charging processes, occurring in a microsecond time frame. The capabilities of this technique enable experiments that cannot be performed using traditional measurements of surface potentials. For instance, in existing measurements the scanning probe disturbs the surface that is being measured, making it difficult to measure charges, such as electrons, that are only weakly confined to an area of the surface. In contrast, the measurements made in this project will be much less disruptive to the surface, making it possible to observe phenomena such as Wigner localization of electrons. The project also involves an outreach program that will target middle school students in South Bend Schools through classroom activities involving faculty and graduate students, and field trips to bring students to the Notre Dame labs. These activities will contact 50 - 100 students per year. Middle school aged children are an excellent group for outreach since they are advanced enough to understand science, but are still making choices about their areas of interests. South Bend public schools have a diverse student population with a large number of students from groups underrepresented in the areas of science and technology.This project will use ultra-sensitive electrometers coupled to a scanned probe system to map the potential of material surfaces. In surface potential measurements, two methods dominate: Kelvin Probe Force Microscopy (KPFM) and Electrostatic Force Microscopy (EFM). Kelvin probe is the more popular technique because it produces a quantitative measurement of the contact potential difference (CPD) while EFM can measure only qualitative changes in CPD. This project design and fabricate scanning single-electron transistor probes (S-SETs) and use them to characterize the surface charge and potential of semiconductor surfaces. The S-SET probes will use radio-frequency reflectometry to enable measurements of the CPD with high charge and potential sensitivity, as well as high spatial and temporal resolution. Arrays of SETs will be used to provide improved immunity to random background charge fluctuations, and to provide improved matching to the RF circuit, eliminating the need for a complicated resonant network. In addition, the use of an RF SET will enable a Kelvin force measurement, not yet reported in the literature, that will be less invasive than those made by conventional KPFM. With the scanned probe system it will be possible to characterize a variety of surfaces including semiconductors and insulators. In particular, the system will be used to investigate Wigner localization of electrons within semiconductor quantum dots.

该项目将使用与扫描针耦合的超灵敏电荷探测器（类似于原子力显微镜）来绘制固体或软材料表面电势的纳米级分辨率图。 将使用基于最灵敏电荷检测器高速版本的单电子晶体管（SET）的新型传感器。该传感器采用 SET 阵列和射频反射计来提供有关在微秒时间内发生的快速充电过程的信息。 该技术的功能使得能够进行使用传统表面电势测量无法进行的实验。 例如，在现有的测量中，扫描探针干扰了正在测量的表面，使得难以测量仅仅微弱地限制在表面区域内的电荷，例如电子。 相比之下，该项目中进行的测量对表面的破坏要小得多，从而可以观察电子维格纳局域化等现象。 该项目还涉及一项外展计划，该计划将针对南本德学校的中学生，通过教师和研究生参与的课堂活动以及带学生参观圣母大学实验室的实地考察。这些活动每年将接触 50 - 100 名学生。中学生是一个很好的外展群体，因为他们已经足够了解科学，但仍在选择自己感兴趣的领域。南本德公立学校拥有多元化的学生群体，其中大量学生来自科学技术领域代表性不足的群体。该项目将使用与扫描探针系统耦合的超灵敏静电计来绘制材料表面的电位图。 在表面电位测量中，主要有两种方法：开尔文探针力显微镜 (KPFM) 和静电力显微镜 (EFM)。开尔文探针是更流行的技术，因为它可以定量测量接触电位差 (CPD)，而 EFM 只能测量 CPD 的定性变化。该项目设计和制造扫描单电子晶体管探针（S-SET），并用它们来表征半导体表面的表面电荷和电势。 S-SET 探头将使用射频反射仪来实现具有高电荷和电位灵敏度以及高空间和时间分辨率的 CPD 测量。 SET 阵列将用于提高对随机背景电荷波动的抗扰度，并改善与 RF 电路的匹配，从而消除对复杂谐振网络的需要。 此外，使用 RF SET 将能够进行开尔文力测量（尚未在文献中报道），这比传统 KPFM 进行的测量侵入性更小。 通过扫描探针系统，可以表征包括半导体和绝缘体在内的各种表面。 特别是，该系统将用于研究半导体量子点内电子的维格纳局域化。