Interaction between Quantum-Confined Excitons and Lattice in Semiconductor Ultrafine Particles

在半导体超细粒子中，为了理解量子尺寸对电子态、晶格振动和相互作用的影响，寻找各种尺寸相关和表面敏感的现象是很重要的。在本研究项目中，我们研究了CuCl量子点的光学性质，其中激子的平移运动主要受到限制。在受限几何中，得到了激子-晶格相互作用的结果。1. 通过监测限制激子发光的尺寸和温度相关的均匀线宽，获得了激子-晶格相互作用的尺寸依赖性。由于变形型相互作用的短程性，激子与声振动的相互作用随着点尺寸的减小而增大。2. 光疲劳效应，表现为激子的发光强度随着激光的长期照射而降低。这种效应的起源是由于表面晶格松弛导致激子捕获中心的形成。3. 通过观察激子吸收和发光的非线性变化，探讨了高密度激子效应与激子光学非线性的关系。光学非线性主要是由受限激子之间的相互作用引起的，这种非线性随点半径的增加而增加，至少在5nm以内。通过比较嵌入在NaCl基体和硼硅酸盐玻璃基体中的CuCl量子点中量子约束激子的光学性质，研究了基体效应。从以上结果可以看出，激子-晶格相互作用对CuCl量子点的光学性质起着重要的作用。借助目前的结果，我们可以期望更多地了解半导体量子点及其密集聚集的新性质。少

In semiconductor ultrafine particles, it is important to look for various size-dependent and surface-sensitive phenomena in order to understand the quantum size effects on the electronic states, lattice vibrations and the mutual interactions. In this research project, we have investigated the optical properties of CuCl quantum dots, in which the exciton translational motion is mainly confined. The following results have been obtained concerning the exciton-lattice interactions in the restricted geometries. 1. Size-dependence of the exciton-lattice interaction has been obtained by monitoring the size- and temperature-dependent homogeneous linewidth of the confined exciton luminescence. The interaction between exciton and acoustic vibration increases with the decrease of the dot size due to the short-range character of the deformation-type interaction. 2. Photofatigue effect which appears as the reduction of the exciton luminescence intensity with the long-term exposure to the laser ligh … More t. The origin of this effect is concluded to be due to the formation of the exciton trapping center as a result of lattice relaxation on the surface. 3. Relation between high density exciton effects and excitonic optical nonlinearities has been invest igated through the observation of the nonlinear changes of excion absorption and luminescence. The optical nonlinearities are mainly caused by the mutual interaction between confined excitons, which increases with increase of the dot radius at least up to 5nm. 4. Matrix effect has been studied through the comparison of the optical properties of quantum-confined excitons in CuCl quantum dots embedded in NaCl matrix with those in borosilicate glass matrix.From the above results, the exciton-lattice interaction is concluded to play important roles in the optical properties of CuCl quantum dots. With the aid of the present results, we can expect to understand more about the new properties of semiconductor quantum dots and their dense aggregation. Less