范德华异质结微纳结构光电性能的多域分辨超快动力学研究

In recent years, the van der Waals heterojunction nanostructures featuring both structural and electronic diversities have attracted much attention. However, the existing investigations on the photoelectric properties and the relevant mechanisms of such materials under realistic working conditions remain meager. To this end, this project is aimed, on the basis of the multi-domain (time/energy/space) resolved ultrafast spectroscopy and dynamics platform that has been established in our group, to gain mechanistic insights into various processes/effects associated with charge carriers, excitons, and plasmons in several, selected model systems of van der Waals heterojunction nanostructures (e.g., those composed of graphene, molybdenum disulfide, and black phosphorus) under realistic working conditions (e.g., temperature and electric field). The tools we use will be a combination of optical spectroscopy (mainly including ultrafast transient absorption and steady-state/time-resolved fluorescence) and high-resolution local-space detections based on near-field scanning microscopy, with the assistance of some other routine characterizations (such as SEM, TEM, XRD, and XPS) and theoretical modeling/simulations. The fundamental understanding obtained through this project would provide valuable guidance for rational design of materials/devices based on van der Waals heterojunction nanostructures.

近年来，兼具结构多样性和电子多样性的范德华异质结引起了人们的广泛关注。然而，在实际器件工作条件下，范德华异质结光电性能的机理研究仍很匮乏。本项目拟在本课题组已建立和发展的多域（能域/时域/空间域）分辨谱学和动力学测试平台上，选择若干倍受关注的范德华异质结微纳结构（如石墨烯、二硫化钼、黑磷等新兴材料所形成的异质结）作为模型体系，通过调控其实际器件的不同工作条件（温度、电场等），采用超快瞬态吸收、稳态/瞬态荧光光谱与基于近场微区扫描的局域空间高分辨探测相结合的技术，并辅以其他表征手段（如SEM、TEM、XRD、XPS等）和理论建模，全面而深入地研究并理解与范德华异质结微纳体系光电性能密切相关的微观作用机制（如载流子、激子、等离激元等过程和效应的超快演化、空间分布、内在关联等），从而为该类材料体系的理性设计和优化提供来自机理层面的解读和指导。

本项目顺利完成了三年执行期的研究内容和研究目标。在技术层面上，我们自主设计和建立了集成了光谱和显微表征的多域（能量、空间、时间）高分辨率超快表征研究平台，为高效获取异质结材料谱学（能量）和空间映射以及时间演化方面的信息打下了良好的基础。我们已在该集成平台上实现了若干原理验证性实验，包括原位集成吸收、反射等检测模式的超快时间光谱、拉曼成像（高分辨拉曼、偏振拉曼、低波数拉曼）、时间分辨光致发光成像和光电性能成像等。在科学层面上，我们利用新建立的多域分辨超快表征平台，辅以其他测试手段和理论模拟，我们深入而系统地研究了若干模型体系（石墨烯、钌/二氧化钛、掺氢金属氧化物、酮类分子/聚合氮化碳、金属有机发光体等）所涉各种激发态行为效应和作用机制，获得了对异质结材料体系中载流子/表界面电荷转移动力学（如：载流子输运、光生缺陷电子、能量传递等）、光致发光的热淬灭和负热淬灭相关效应和元激发效应机制（如：激子动力学、声子/极化子/等离激元动力学等）的深层次理解，从而为相关材料体系的实用研发提供重要的来自微观机理层面的启发和指导。