单层/少层二维纳米薄片的可控组装与光电性能研究

Heterostructures formed by vertically stacking various two-dimensional nanosheets, such as graphene and transition metal dichalcogenides (TMDs), offer promising properties and functionalities for many electronic and optoelectronic applications. Interfacial interactions in heterostructures are assumed to play an important role in offering these novel properties and functionalities. The interfacial interaction is highly depended on the thickness, stacking angle and order of nanosheets. To date, many studies focus on the stacking angle and order of nanosheets with limited thickness. However, the influence of thickness on interfacial interaction remains largely unexplored. In this project, 2D nanosheets with various thickness, such as graphene and TMDs, will be prepared by mechanical exfoliation in the first step. Subsequently, nanosheets with desired thickness will be stacked under controlled angle and order by using a clean transfer technique. The influence of thickness, stacking angle and order on the interfacial interaction will be systematically investigated by using low-frequency Raman spectroscopy. Key factors for interfacial interaction will be found out. Devices will be made based on as-prepared heterostructures with desired interfacial interactions. Photoresponse of these devices will be measured to demonstrate the relationship between device performance and interfacial interaction. We hope to thoroughly understand the influence factors of interfacial interaction between nanosheets and control the optoelectronic performance of heterostructures based on our results. It will pave the way for the theoretical design and development of heterostructures for many electronic and optoelectronic applications.

两种或多种二维纳米薄片组装形成的异质结展现出许多不同于单种二维纳米薄片的新奇物理性质和优异器件性能，在光电器件领域有着广阔的应用前景。纳米薄片之间的层间相互作用受薄片厚度、组装角度和次序影响，并决定了异质结的性能。目前的研究局限在少数厚度二维纳米薄片的组装角度或次序方面，未能系统研究二维纳米薄片厚度的影响。本课题拟采用机械剥离法精确制备具有不同厚度的石墨烯和过渡金属硫族化合物二维纳米薄片，结合洁净纳米材料转移技术实现对纳米薄片的厚度、组装角度和次序的可控组装，运用超低波数拉曼光谱仪详细研究各种因素对层间相互作用的影响，深入探索影响层间相互作用的关键因素，阐述其对异质结光电性能的影响，揭示纳米薄片的组装结构与性能的内在关系。本研究不仅对理解异质结中各种二维纳米薄片的相互作用具有直接意义，而且有助于实现对异质结性能的精确调控，有望为设计并制备高性能的异质结光电器件提供新的理论依据和技术手段。

两种或多种二维纳米薄片组装形成的异质结展现出许多不同于单种二维纳米薄片的新奇物理性质和优异器件性能，在光电器件领域有着广阔的应用前景。纳米薄片之间的层间相互作用受薄片厚度、组装角度和次序影响，并决定了异质结的性能。目前的研究局限在少数厚度二维纳米薄片的组装角度或次序方面，未能系统研究二维纳米薄片厚度的影响。本课题以石墨烯与过渡金属硫属化合物（TMDCs，二硫化钼、二硒化钨和二硫化钨）的单层和少层纳米薄片形成的范德华异质结（vdWHs）为研究对象，利用超低频（ULF）拉曼光谱仪、原子力显微镜和光学显微镜等仪器，通过观察vdWHs中TMDCs纳米薄片的超低频拉曼呼吸模式的变化，系统地研究了纳米薄片厚度、叠放次序和叠放角度对石墨烯和TMDCs纳米薄片vdWHs的层间相互作用的影响。在二硫化钼和二硒化钨与石墨烯形成的异质结中，呼吸模式拉曼信号随石墨烯厚度的增加而发生红移，同时伴有新的呼吸模式出现，但是其剪切振动信号一直维持稳定。纳米薄片的堆叠次序不影响石墨烯/二硫化钼异质结的层间相互作用，而对石墨烯和WSe2异质结中的层间相互作用产生较大影响。二硫化钨和石墨烯异质结的拉曼信号不受石墨烯厚度的影响。此外，我们的研究结果表明，层间相互作用随堆叠角度变化并未发生明显的变化。本课题的研究结果对范德华异质结层间相互作用的理论研究和应用具有很好的指导意义。