Strain Effects in Transition Metal Dichalcogenide Field-Effect Transistors

标题：单层过渡金属双硫化物场效应晶体管中的应变效应应变是电子器件设计和性能中的一个重要变量。它不仅在推动硅技术的发展方面发挥了核心作用，而且还在继续推动诸如应变电子学和电子皮肤等全新类型的设备。与块体半导体相比，单层过渡金属二硫族化合物（TMDs）由于其原子厚度而与应变具有相当丰富的关系。这不仅允许这些材料获得微机械Si无法实现的变形，而且还导致应变成为许多常见设备加工步骤的无意工件。该项目将研究应变对具有单层TMD通道的场效应晶体管（fet）的影响，这可以提高这些器件的性能极限，并解决与有害应变相关的主要集成和可靠性挑战。从该项目中提取的知识将通过位于研究者所在大学的教育中心卡鲁斯工程教育研究所（CIEE）支持该地区的K-12科学、技术、工程和数学（STEM）项目。这包括在CIEE举办的动手暑期校园的发展，以及为该地区的学区制定与stem相关的课程计划，以促进工程的多样性。本项目的目标是对应变对单层tmd及其接触处的低场和高场输运的影响进行严格的研究。该研究在电子器件领域具有变革性的潜力，因为应变可以显著调节能带结构，在低场输运中驱动创纪录的压阻效应，在高场输运中调节饱和速度。此外，新的定量知识在接触应变的影响，可以推进技术，如柔性设备，其中接触失败往往是经验描述。除了均匀应变外，短期应变波动对输运的影响也将被表征，并适用于新开发的输运模型。器件将在具有不同通道长度的柔性衬底上制造，这允许通道和触点的解耦。应变将通过机械变形传递，并使用拉曼光谱和光致发光进行表征。电特性将适合于低场（玻尔兹曼输运方程）和高场（多谷蒙特卡罗）输运模型，这些模型考虑了几种散射机制。这包括声子，中性和电荷缺陷，以及一些解释短期应变变化的第一个模型的发展。本项目产生的所有知识将通过出版物传播，并纳入研究者的课程，以达到尽可能广泛的受众。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Title: Strain Effects in Monolayer Transition Metal Dichalcogenide Field-Effect TransistorsStrain is a powerful variable in the design and performance of electron devices. Not only has it played a central role in boosting Si technology, but it continues to enable entirely new types of devices like straintronics and electronic skins. In comparison to bulk semiconductors, monolayer transition metal dichalcogenides (TMDs) have considerably richer relationships with strain due to their atomic thickness. This not only allows these materials to access deformations not possible with micromachined Si, but also results in strain being an unintentional artifact of many common device processing steps. This project will investigate the effects of strain on field-effect transistors (FETs) with monolayer TMD channels, which can advance the performance limits of these devices and solve major integration and reliability challenges associated with deleterious strain. Knowledge distilled from this project will support K-12 science, technology, engineering, and mathematics (STEM) programs in the region through the Caruth Institute for Engineering Education (CIEE), an educational center located at the investigator's university. This includes the development of hands-on summer campus hosted at CIEE, and the development of STEM-related lesson plans for school districts around the region that promote diversity in engineering.The goal of this project is to provide a rigorous investigation of the effect of strain on the low-field and high-field transport in monolayer TMDs and at their contacts. The proposed research has potential to be transformative in the field of electronic devices as strain can dramatically modulate the band structure, driving record piezoresistive effects in the low-field transport and tuning saturation velocity in the high-field transport. Furthermore, new quantitate knowledge on the effects of strain at contacts can advance technologies such as flexible devices, where contact failure is often described empirically. In addition to the uniform strain, the effects of short-range strain fluctuations on the transport will be characterized and fit to newly developed transport models. Devices will be fabricated on flexible substrates with varying channel lengths, which allows for a decoupling of the channel and contacts. Strain will be imparted using mechanical deformations, and characterized using Raman spectroscopy and photoluminescence. Electrical characterizations will be fit to low-field (Boltzmann Transport Equation) and high-field (multivalley Monte Carlo) transport models that account for several scattering mechanisms. This includes phonons, neutral and charge defects, and the development of some of the first models to account for short-range strain variation. All knowledge generated by this project will be disseminated through publications and inclusions in the investigator's courses to reach the broadest possible audience.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.