Conjugated Energy Transport and Hot Carrier Diffusion in 2D Transition Metal Dichalcogenides: Novel Characterization toward Fundamental Understanding

二维过渡金属二硫属化物（TMD）是具有极小厚度（低至几个原子水平）的材料。它们具有广泛的应用，包括柔性电路、传感器和低功率晶体管。它们的热物理性能和能量传输能力直接决定了它们的性能和耐久性。此外，它们的电子转移速率是直接决定器件功能的性质。本计画利用超快雷射与连续雷射激发与探测TMD分子振动模式（拉曼光谱信号），并利用此信号来区分与表征TMD的热物理性质、电子传递速率与界面能量传递能力。该项目的成果应建立关键的知识基础，需要在TMD结构剪裁，器件设计和热优化。此外，该项目通过课堂教学和新课程模块开发将研究活动融入教育，促进少数民族学生的研究培训，并通过各种外联活动，包括科学博览会，实验室参观，并提供高中教师研究经验。本项目的目标是进一步部署一种新的能量传输状态-解决了拉曼表征热载流子扩散率，声子热导率，界面热阻支持的TMD，和单层TMD的电子空穴非辐射复合系数。该项目研究了物理结构对三种输运过程的影响：热载流子扩散，面内声子输运和跨界面能量输运（对于支持的TMD），研究了衬底对性能的影响，并探索了温度（70 K至850 K）对性能的影响。这代表了二维材料中热载流子输运和辐射电子-空穴复合的第一个和高精度的考虑。该项目极大地促进了2D TMD缺陷工程领域的发展，并为这一新兴领域的挑战和机遇提供了前沿视角。该奖项反映了NSF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。

Two-dimensional transition metal dichalcogenides (TMDs) are materials that have an extremely small thickness (down to a few atoms level). They have broad applications including flexible circuits, sensors, and low power transistors. Their thermophysical properties and energy transport capability directly determine their performance and durability. Also, their electron transfer rate is a property that directly determines device functionality. This project uses ultrafast lasers and a continuous laser to excite and probe the molecular vibrations modes (Raman spectroscopic signal) of TMDs, and use such signals to distinguish and characterize the thermophysical properties, electron transfer rate, and interface energy transfer capability. The outcome of the project should establish the critical knowledge base needed in TMDs structure tailoring, device design, and thermal optimization. Furthermore, the project integrates research activities into education via classroom teaching and new class module development, fosters minority student research training, and stimulates research interests of K-12 students by various outreach activities including science fair, lab tour, and providing high-school teacher research experience.The goals of this project are to conduct further deployment of a novel energy transport state-resolved Raman to characterize hot carrier diffusivity, phonon thermal conductivity, interface thermal resistance for supported TMDs, and electron-hole nonradiative recombination coefficient for monolayered TMDs. The project investigates the effect of physical structure on the three transport processes: hot carrier diffustion, in-plane phonon transport, and cross-interface energy transport (for supported TMDs), studies the effect of substrate on properties, and explores the effect of temperature (70 K to 850 K) on properties as well. This represents the first and high precision consideration of hot carrier transport and radiative electron-hole recombination in 2D materials. This project significantly promotes the field of defect engineering in 2D TMDs, and provides frontier perspective on the challenges and opportunities in this emerging field.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.