Exciton Dynamics and the Electronic Structure of CdSe/ZnSe Quantum Dots

这个凝聚态物理项目利用时间分辨光谱仪以及高空间和能量分辨光谱仪来探测单个CdSe/ZnSe自组装量子点的电子态的静态和动态特性。用共振光谱、拉曼光谱和光致发光光谱研究了电子能级的激发态结构。偏振光致发光和磁场效应将被用来识别状态的对称性。用时间分辨光致发光或抽运探测皮秒/飞秒激发研究了量子点电子态之间的跃迁动力学。特别令人感兴趣的是紧密相关量子点之间相互作用的物理学，以及激发与光学和声学光子的相互作用。参与这项研究的本科生和研究生将接受关于合成和表征纳米结构材料的现代最先进技术的培训。这个凝聚态物理项目使用光学方法来研究电子和空穴，这些电子和空穴被限制在纳米结构中，其长度尺度与粒子的波动性质相当。这样的量子点可以通过利用大自然自我组织的倾向来制造。就像露水不会持续地湿润树叶，而是经常组织成一层液滴一样，硫化镉沉积在硒化锌表面时，会形成小的纳米级固体颗粒，因为它们的尺寸很小，所以被称为量子点。近年来的大量实验表明，这些结构将电子限制在使人联想到原子或分子中的电子态的状态。量子点中的电子态不像分子电子态那样被理解，量子点态可以通过改变量子点的大小和组成来调节。该项目将在很大程度上使用高分辨率光学技术来探测量子点中电子的能量结构和动力学。与该项目相关的研究生和本科生将接受制造和表征纳米结构材料的最先进技术方面的培训。

This condensed matter physics project utilizes time-resolved spectroscopies, and high spatial- and energy-resolved spectroscopies to probe the static and dynamic character of electronic states of individual CdSe/ZnSe self-assembled quantum dots. The excited state structure of the electronic levels will be probed by resonant, Raman and photoluminescence spectroscopies. Polarized photoluminescence and magnetic field effects will be used to identify the symmetry properties of the states. Dynamics of transitions among the quantum dot electronic states are studied by time-resolved photoluminescence or pump-probe picosecond/femtosecond excitations. Of particular interest is the physics of interactions between closely associated quantum dots as well as interactions of excitations with optic and acoustic photons. The undergraduate and graduate students involved in this research will be trained in modern state-of-the-art techniques for synthesizing and characterizing nanostructured materials.%%%This condensed matter physics project use optical methods to electrons and holes which are confined to nanostructures where the length scale is comparable to the wave nature of the particles. Such quantum dots can be made by utilizing the tendency of nature to 'self organize' itself. Just as dew does not continuously wet a leaf but often organizes into a layer of droplets, cadmium sulfide when deposited on a zinc selenide surfaces forms small nanoscale solid particles which are know as quantum dots because of their small size. Extensive experiments in recent years have shown that these structures confine electrons to states that are reminiscent of the electron states in atoms or molecules. The electronic states in the quantum dots are not as well understood as the molecular electronic states, ant the quantum dot states can potentially be tuned by varying the size and composition of the dots. This project will largely use high resolution optical techniques to probe the energy structure and dynamics of electrons in the quantum dots. Graduate students and undergraduate students associated with the project will be trained in state-of-the-art techniques for making and characterizing nanostructured materials.