CAREER: Strain-driven phase transitions in 2D van der Waals based devices

提案标题CAREER：二维范德华器件中的应变驱动相变非技术摘要传统上计算进步的焦点强烈依赖于组成几乎所有集成电路的场效应晶体管(FET)的持续缩小。由于晶体管定标的基本物理和经济极限现已达到，人们正在探索新的器件类型，以便在传统晶体管开关的基础上增加功能。该项目探索了应变在二维(2D)结合材料中的应用，因此施加拉伸或压缩可能会在这些系统中引起各种相变。由于这些相变并不像传统晶体管的导通/关断状态那样局限于导电和非导电，因此可以通过应变下材料属性的其他变化来实现额外的功能。这种类型的应变感应型相变器件不会在与传统晶体管相同的物理机制下工作，因此不会受到相同的限制。通过影响现代纳米电子的构建块，可能会对计算技术的各个方面产生巨大影响，而这些方面目前由于传统晶体管的各种功率、速度或效率限制而受到限制。该项目还试图利用研究框架，通过与罗切斯特大学伊士曼音乐学院的联系，向传统上代表性不足的社区推广科学、技术、工程和数学(STEM)。活动的例子包括为当地7-12年级的学生开设音乐和电子方面的暑期教育课程，以创造可用于现场音乐会表演的非传统乐器。技术摘要本项目旨在了解在二维(2D)结合材料中使用器件规模的栅极可控应变来制造新型相变晶体管的基本原理。通过探索一种使用应变的晶体管开关的新机制，可以克服与常规场效应晶体管操作相关的限制。由于二维材料类中的各种相接近应变可调相变，因此存在着为各种门可控的奇异物质状态奠定基础的机会。本项目中使用的设备平台使用铁电氧化物施加的动态应变与静态薄膜应力封顶层相结合来演示MO1-xWxTe2类二维材料的相变。以MoTe2从半金属到半导体的相变为起点，确定了可能仍然限制在2D系统中实施可靠的动态器件规模应变的关键问题，目标是将这种“紧致”概念扩展到更持久、更高成品率的操作，以及在Mo1-xWxTe2类材料中添加新的相来控制。此外，从单个2D系统的室温操作中学习的基本概念允许将这种动态应变工程概念转化为低温和van der Waals异质结构，广泛扩展了动态应变工程在2D系统中的适用性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Proposal TitleCAREER: Strain-driven phase transitions in two-dimensional van der Waals based devicesNon-technical AbstractThe conventional focus for advancements in computing have strongly relied on the continued shrinking of the field-effect transistors (FET) that makes up almost all integrated circuits. Since the fundamental physical and economic limits of transistor scaling are now being reached, new types of devices are being explored for added functionality beyond conventional transistor switching. This project explores the use of strain in two dimensionally (2D) bonded materials, such that applied stretching or compression may induce various phase-changes in these systems. Since these phase-changes are not limited to electrically conducting versus non-conducting as in on/off states of conventional transistors, additional functionality may be engineered through other changes in materials properties under strain. This type of strain-induced phase-change device would not operate under the same physical mechanism as conventional transistors, and therefore are not subject to the same limitations. By impacting the building blocks of modern nanoelectronics, there may be large impacts in various aspects of computing technology that are currently limited due to various power, speed, or efficiency limitations of conventional transistors. This project also seeks to use the research framework to promote science, technology, engineering and mathematics (STEM) to traditionally underrepresented communities by connecting with the Eastman School of Music at the University of Rochester. Examples of activities include running summer educational courses in music and electronics to local grade 7-12 students to create unconventional instruments that may be used in live concert performances.Technical AbstractThis project seeks to understand the foundational principles of using device-scale gate-controllable strain in two-dimensional (2D)-bonded materials to create new types of phase change transistors. By exploring a new mechanism of transistor switching using strain, limitations associated with conventional field-effect transistor operations may be overcome. With the wide variety of phases in the two-dimensional materials class close to strain-tunable phase transitions, the opportunity exists to set the basis for a wide variety of gate-controllable exotic states of matter. The device platform used in this project uses dynamic strain applied from ferroelectric oxides in combination with static thin film stress capping layers to demonstrate phase-switching in the Mo1-xWxTe2 class of two-dimensional materials. Using the MoTe2 semimetallic to semiconducting phase transition as a starting point, critical issues are identified that may still limit the implementation of reliable dynamic device scale strain in 2D systems, with the goal of expanding this "straintronic" concept to higher-endurance higher-yield operation as well as adding new phases to control within the Mo1-xWxTe2 class of materials. Additionally, learned foundational concepts from room-temperature operation in single 2D systems allow for the translation of this dynamic strain engineering concept to low temperatures and to van der Waals heterostructures, widely expanding the applicability of dynamic strain engineering in 2D systems.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.