表面依赖的半导体量子点非线性光学性质研究

The experimental and theoretical studies clearly demonstrate the effect of the surface states on the steady-state and time-resolved PL spectra of colloidal quantum dots (QDs) in multifarious situations, but comparatively little is concerned about the two-photon absorption and refraction involved in the surface traps. To explore the origin of the QDs’ surface-dependent nonlinear optical (NLO) process is a challenging task and has great significance to describe the surface structures of these colloidal nanostructures as well as to improve the performance of QDs’ devices. The surface states can be modified by overcoating the QDs with large-bandgap semiconductor layers, so it is convenient to study how the surface states affect the NLO properties by using the core/shell NCs. In this project, the surface-dependent NLO absorption and refraction of the QDs will be investigated by Z-scan technology and other nonlinear optical measurements. The QDs’ surface will be modified by using the size control and overcoating CdS monolayers (MLs) on cores, and the surface states will be characterized by transmission electron microscopy (TEM)/ high-resolution transmission electron microscopy (HRTEM)/ X-ray diffraction (XRD) and absorption/fluorescence spectrum. This work will shed light on comprehending the physical mechanism of the surface states and surface-related optical nonlinearity of semiconductor QDs.

现有的实验和理论研究清晰地证明了半导体量子点的表面态在稳态和时间分辨荧光谱中的作用，然而相比而言，很少关心涉及表面态的非线性吸收和折射。研究量子点表面依赖的非线性光学过程的机制是一个富有挑战性的工作，在描述表面结构和提高量子点器件性能都非常重要。除了裸核量子点具有不同的表面态以外，在量子点外包覆大带隙半导体层可以修饰表面态，因此利用核壳结构量子点也可以方便的研究表面态是如何影响光学非线性性质的。本项目中拟通过调控尺寸和包覆相同层数的壳来改变量子点的表面，用形貌、结构、光谱和动力学等多种手段表征量子点表面结构，用Z扫描等多种非线性技术测量表面依赖的量子点非线性光学性质，理论拟合结合实验分析机制。为深入揭示量子点表面结构与非线性光学机制提供重要实验手段和理论依据。

现有的实验和理论研究清晰地证明了半导体量子点的表面态在稳态和时间分辨荧光谱中的作用，然而相比而言，很少关心涉及表面态的非线性吸收和折射。研究量子点表面依赖的非线性光学过程的机制是一个富有挑战性的工作，在描述表面结构和提高量子点器件性能都非常重要。除了裸核量子点具有不同的表面态以外，在量子点外包覆大带隙半导体层可以修饰表面态，因此利用核壳结构量子点也可以方便的研究表面态是如何影响光学非线性性质的。本项目中拟通过调控尺寸和包覆壳来改变量子点的表面，用形貌、结构、光谱等多种手段表征量子点表面结构，用Z扫描等多种非线性技术测量表面依赖的量子点非线性光学性质，理论拟合结合实验分析机制。为深入揭示量子点表面结构与非线性光学机制提供重要实验手段和理论依据。