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

在半导体超微粒子中，寻找各种尺寸依赖和表面敏感现象对于理解量子尺寸对电子态、晶格振动和相互作用的影响是很重要的。在本研究计划中，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。得到了限制几何条件下激子-晶格相互作用的结果。1.尺寸依赖性的激子晶格相互作用已经得到通过监测的尺寸和温度依赖的均匀线宽的限制激子发光。由于形变型相互作用的短程特性，激子与声振动之间的相互作用随着量子点尺寸的减小而增强。2.光疲劳效应是指长时间暴露在激光光下，激子发光强度降低， 关于我们 t.这种效应的起源被推断为由于在表面上的晶格弛豫的结果，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，研究了高密度激子效应与激子光学非线性的关系。量子点的光学非线性主要是由受限制激子之间的相互作用引起的，在5 nm以下，激子之间的相互作用随量子点半径的增大而增大。4.通过比较嵌在NaCl和硼硅酸盐玻璃中的CuCl量子点中量子限制激子的光学性质，研究了CuCl量子点的基质效应，得出激子-晶格相互作用对CuCl量子点的光学性质起重要作用的结论.借助这些结果，我们可以期望更多地了解半导体量子点及其密集聚集体的新特性。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