相互扩散和晶格失配对核/壳结构半导体纳米复合颗粒光谱和动力学性质的影响

Due to their high fluorescent quantum yield and good photostability, semiconductor nanocrystals with a core/shell structure have been extensively investigated. However, owing to the difference in the lattice mismatch between core and shell materials, the growth of shell would greatly change the dimensions of the core and shell materials. Additionally, because the core/shell semiconductor nanocrystals are usually synthesized at the relatively high temperatures, which will induce the occurrence of interdiffusion of the core/shell materials and change the composition of the core/shell materials along their radial direction. The spectroscopic and dynamic properties of the core/shell semiconductor nanocrystals are greatly dependent upon their dimension and composition, due to the quantum confinement effect. In this sense, the lattice mismatch and the interdiffusion will change the spectroscopic and dynamic properties of the core/shell semiconductor nanocrystals. Up to now, although the lattice mismatch and interdiffusion have been noticed in the core/shell semiconductor nanocrystals, the detailed investigation of their effects on the spectroscopic and dynamic properties of the core/shell semiconductor nanocrystals have been less reported in the literatures. The present project is therefore proposed to investigate the effects of the lattice mismatch and interdiffusion on the spectroscopic and dynamic properties of the core/shell semiconductor nanocrystals. The influence of the lattice mismatch and interdiffusion on the distribution of electron and hole wave functions and the positions of conduction and valence band edges will be studied, which is of great significance for designing and controlling of the properties of the core/shell semiconductor nanocrystals and improving the performance of semiconductor quantum devices.

核/壳结构半导体纳米复合颗粒具有荧光量子产率高和稳定性高等优点，是纳米材料领域的研究热点。但由于组成核/壳结构纳米复合颗粒的核和壳材料之间存在晶格参数的差异，壳的生长将改变核和壳材料的尺寸。另外，由于这种半导体纳米复合颗粒通常在高温下合成。高温容易导致核和壳材料的相互扩散。相互扩散将改变纳米复合颗粒沿径向的组成。半导体纳米复合颗粒的光谱和动力学性质与其尺寸和组成密切相关。由此可见，晶格失配和相互扩散将影响核/壳结构半导体纳米复合颗粒的光谱和动力学性质。到目前为止，尽管晶格失配和相互扩散对核/壳结构半导体纳米复合颗粒的影响已受到科技工作者的注意，但晶格失配和相互扩散影响其光谱和动力学性质的详细研究相对较少。因此，本项目将着重研究晶格失配和相互扩散对核/壳结构半导体纳米复合颗粒光谱和动力学性质的影响，这对设计和调控颗粒的性质、提高半导体量子器件的性能具有十分重要意义。

核/壳结构的半导体纳米颗粒具有荧光量子产率高、稳定性高、吸光范围可调等优点，是半导体纳米材料领域和半导体量子器件领域的研究热点。但由于核/壳结构半导体纳米颗粒通常在高温有机溶液中合成，核和壳材料之间易发生相互扩散，从而改变纳米颗粒组成、光学性质以及光生载流子的动力学过程。此外，由于组成纳米颗粒的核和壳材料之间存在晶格失配，晶格失配易引起核和壳之间的界面应力,从而进一步影响纳米颗粒的光学和光生载流子的动力学过程。本项目主要研究了相互扩散和晶格失配对核/壳结构半导体纳米颗粒组成、光学性质、电子/空穴的波函数分布和光生载流子动力学过程的影响，具体研究内容包括：1）反应温度对相互扩散速度和核/壳结构半导体纳米颗粒沿粒子径向组成的影响；2）晶格失配引起的应变能的大小以及应变能对纳米颗粒壳均匀性的影响；3）相互扩散和晶格失配对纳米颗粒的光谱性质、电子和空穴的波函数分布、以及能量最高价带和能量最低导带电位的影响；4）晶格失配和相互扩散对电子和空穴的动力学过程的影响。通过研究，获得了核/壳结构半导体纳米颗粒核和壳材料之间相互扩散速率和纳米颗粒沿径向的组成随温度变化的规律，并获得了核/壳结构半导体纳米颗粒由晶格失配引起的应变能的大小、以及应变能与壳均匀性的关系。建立了数学模型，准确预测了相互扩散和晶格失配对核/壳结构半导体纳米颗粒的光谱性质、电子和空穴的波函数分布、以及能量最高价带和能量最低导带电位的影响规律，并在实验上得到了验证。研究发现，晶格失配的存在将影响纳米颗粒壳的均匀性，从而影响光生载流子的转移动力学，高温热处理可以促进核和壳材料之间的相互扩散，从而改变壳的均匀性。这些研究成果对可控制备半导体纳米颗粒和调控颗粒的光学性质和光生载流子动力学过程具有重要意义，有利于促进核/壳结构半导体纳米颗粒在半导体量子器件中的应用。