基于瞬态吸收显微成像的一维半导体纳米材料的载流子超快动力学研究

Optical properties and ultrafast charge carrier dynamics of one-dimensional semiconducting nanomaterials need to be thoroughly understood before their practical applications in optoelectronic devices. In order to obtain extremely weak optical signals from these tiny nanomaterials, most researches were performed on a large amount of nanomaterials with certain size and/or structure distributions, making the experimental observations difficult to be analyzed and interpreted unambiguously and quantitatively with physical models. Base on the above considerations, individual one-dimensional semiconducting nanomaterials and their dimers (including single-walled carbon nanotubes and II-VI group compounds) with known sizes will be interrogated by transient absorption microscopy in the project. Transient absorption spectra near the band gap energies and charge carriers dynamics will be collected in individual one-dimensional semiconducting nanomaterials with known sizes. From the experiments, It is expected to quantitatively dig out the charge carriers decay and diffusion dynamics in these one-dimensional nanomaterials and the precise relations between the dynamics and the size/structure. Besides, the tuning of charge carriers dynamics by covalent and noncovalent modification will be investigated. Furthermore, individual dimers will be studied to clarify the interactions between the two adjant one-dimensional semiconducting nanomaterials and how the charge carriers transfer to and from each other.

一维半导体纳米材料的光电器件化应用需要深入理解其光学性质和载流子的超快动力学行为。为了克服纳米材料尺寸微小、光学信号微弱的缺点，大量的实验研究不得不对具有一定尺寸分布和结构分布的样品展开,使得研究结果很难用精确的和定量的物理模型给予分析和解释。基于以上研究现状和现实考虑，本项目以已知尺寸的单个一维半导体纳米单元和单个二聚体（包括单壁碳纳米管和Ⅱ-Ⅵ族化合物）为研究对象，以瞬态吸收显微成像技术为研究手段，获得已知尺寸的单个一维半导体纳米单元带隙能量附近的瞬态吸收光谱，定量研究载流子的弛豫动力学和扩散动力学，建立这些动力学行为与尺寸和结构的关系和模型，并通过共价和非共价修饰调控载流子的超快动力学行为。同时，我们还将研究一维半导体纳米单元的单个二聚体，定量阐明二聚体内部纳米单元之间的相互作用和载流子在两个纳米单元之间的转移动力学行为。

单层二维材料具有其纵向的量子尺寸效应，以及超高表面原子比例，呈现出与众不同的光学性质和谱学性质，并有望成为未来电学器件和光电器件的重要材料。研究二维材料的激发态动力学和光学性质，可以为其应用提供坚实的基础，并为材料制备指明方向。本项目先后搭建了瞬态吸收显微成像系统和扫描偏振调制显微成像扫描偏振调制显微成像系统；利用瞬态吸收显微成像研究了黑磷、石墨烯等二维材料的激发态动力学，发现基底可以调控二维材料的激发态动力学，并且黑磷的激发态动力学和声学声子都呈现出各向异性；利用扫描偏振调制显微成像系统研究了黑磷、ReS2、MoTe2等各向异性二维材料的光学各向异性，发现二维材料的光学各向异性具有明显的厚度依赖和波长依赖，同时扫描偏振调制技术是一种快速确定二维材料晶格的方法。在样品制备过程中，我们开发了一种基于热化学反应修饰和调控纳米材料的光学性质的方法，并发现通过调控费米能级，可以实现对纳米材料化学修饰的调控；同时，我们还制备了一维有机/无机钙钛矿微米线，研究了其环境稳定性和相变行为，为其未来的器件应用提供了重要的参考。