Stress Modulated Phase Transition in 2D TMDC Materials

二维 TMDC 材料中的应力调制相变

基本信息

批准号：
2308163
负责人：
Wei Gao
金额：
$ 32.62万
依托单位：
Texas A&M Engineering Experiment Station
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-10-01 至 2023-10-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308163&HistoricalAwards=false
关键词：
Stress Modulated Phase Transition 2D

项目摘要

Two-dimensional transition metal dichalcogenide (2D TMDC) are atomically thin materials with a generalized formula of MX2, where M is a transition metal atom (Molybdenum or Tungsten) and X is a chalcogen atom (Sulfur, Tellurium, or Selenium). One layer of M atoms is sandwiched between two layers of X atoms. 2D TMDC can exist in two stable structural phases with different atomic arrangements: semiconducting 2H phase and conducting 1T' phase. The dynamic control of transitions between these two phases through applied mechanical stress can lead to revolutionary device applications such as memory devices, reconfigurable circuits and topological transistors at atomically thin limits. This project will provide fundamental knowledge of the role of the stress field on the atomistic mechanism of phase transitions of 2D TMDC, facilitating the application of phase engineering in next generation 2D electronics and optoelectronics, thereby advancing national health, prosperity, and welfare. Educationally, taking advantage of the large Hispanic student population at University of Texas at San Antonio, the major educational goal of the project is to broaden the participation of underrepresented groups in research, and train them through active research engagement. The mechanism of stress dependent phase transition is that the stress field can be applied to change transition energy barriers and pathways. The barriers determine phase transition rates and pathways reveal the atomistic transition process such as new phase nucleation and propagation. So far, the role of stress on transition behaviors of 2D TMDC is not clear. The central objective of this project is to determine transition barriers and pathways of 2D TMDC as a function of applied stress field, in order to build a mechanics foundation for phase engineering of 2D TMDC at the atomic level. A combined computational and theoretical approach will be employed to achieve this objective. However, it is noted that the existing methods cannot be readily used for this study when one considers the finite deformation of 2D materials. Hence, new methods will be developed. A new computation method, called Finite Deformation Nudged Elastic Band method, will be developed by adding nonlinear mechanics to conventional NEB method, for finding transition barriers and pathways under finite deformation. Meanwhile, since it is time consuming to simulate all possible stress states, there is a need to develop a theory that can predict the barriers. Hence, a new theoretical method, called Finite Deformation Bell Theory, will be developed based on the concept of original Bell theory and continuum mechanics. The methodologies developed in this project can be applied to study phase transitions of other crystalline materials, and more broadly to study mechano-chemical problems beyond phase transitions, such as diffusion, dislocation motion, fracture formation and so on, where the rate dependent transition behaviors in materials are coupled with stress and finite deformation.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.

二维过渡金属二甲化合物（2D TMDC）是原子上薄的材料，具有MX2的广义公式，其中m是过渡金属原子（钼或钨），X是chalcogen原子（硫，滴滴，滴滴，滴滴，或selenium）。一层M原子夹在两个X原子之间。 2D TMDC可以在两个具有不同原子排列的稳定结构相中存在：半导体2H相并进行1T相。通过应用机械应力在这两个阶段之间对过渡的动态控制可能会导致革命性的设备应用，例如记忆设备，可重新配置的电路和原子上较薄的拓扑晶体管。该项目将提供有关压力领域在2D TMDC相变的原子过渡机制中的作用的基本知识，从而促进了相位工程在下一代2D电子和光电子学中的应用，从而促进了国民健康，繁荣和福利。在教育上，该项目的主要教育目标是利用得克萨斯大学圣安东尼奥分校的大量西班牙裔学生群体，是扩大代表性不足的团体参与研究的参与，并通过积极的研究参与来培训他们。依赖压力相变的机理是，应力场可以应用于改变过渡能屏障和途径。屏障确定相变率和途径揭示了原子过渡过程，例如新的相成核和传播。到目前为止，压力对2D TMDC的过渡行为的作用尚不清楚。该项目的核心目的是确定2D TMDC作为应用应力场的函数的过渡障碍和途径，以在原子级建立2D TMDC相位工程的力学基础。将采用合并的计算方法和理论方法来实现这一目标。但是，注意到，当人们考虑2D材料的有限变形时，现有方法不能轻易用于本研究。因此，将开发新方法。将通过将非线性力学添加到常规的NEB方法中，用于在有限变形下找到过渡障碍和途径，将开发一种称为有限变形的弹性频带方法的新计算方法，称为有限变形。同时，由于模拟所有可能的压力状态已经很耗时，因此有必要开发一种可以预测障碍的理论。因此，将根据原始钟理理论和连续性力学的概念开发一种新的理论方法，称为有限变形铃理论。该项目中开发的方法可以应用于研究其他晶体材料的相过渡，更广泛地研究除了相位过渡之外的机械化学问题，例如扩散，脱位运动，断裂形成等，在材料中的速率转变行为与压力和有限的奖励相关。基金会的智力优点和更广泛的影响评论标准。