低强度飞秒激光激发下CdTe和CdTe/CdS核壳量子点的荧光上转换研究  

Up-conversion luminescence of CdTe and CdTe/CdS quantum dots excited by femtosecond laser of low intensity

作　　者：安利民[1,2] 杨延强[1] 宋维斯[1] 苏文辉[1] 曾庆辉[3] 朝克夫[3] 孔祥贵[3] 

机构地区：[1]哈尔滨工业大学物理系,凝聚态科学与技术研究中心,哈尔滨150001 [2]黑龙江大学物理科学与技术学院,哈尔滨150080 [3]中国科学院长春光学精密机械与物理研究所激发态物理重点实验室,长春130033

出　　处：《物理学报》2009年第11期7914-7920,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10674034;60478015;60771051;60601014;20603035);国家高技术研究发展计划(批准号:2006AA03Z335);黑龙江省教育厅项目(批准号:11533047)资助的课题~~

摘　　要：利用400nm和800nm不同波长的低强度飞秒激光,对CdTe和CdTe/CdS核壳量子点溶胶进行激发,研究其稳态和时间分辨荧光性质.800nm飞秒激光激发下,CdTe和CdTe/CdS核壳量子点产生上转换发光现象,上转换荧光峰与400nm激发下的荧光峰相比蓝移最多达15nm,而且蓝移值与荧光量子产率有关.变功率激发确认激发光功率与上转换荧光强度间满足二次方关系,时间分辨荧光的研究表明荧光动力学曲线服从双e指数衰减.提出表面态辅助的双光子吸收模型是低激发强度上转换发光的主要机理.CdTe和CdTe/CdS核壳量子点荧光由带边激子态和诱捕态两种成分组成,两种成分峰位不同,带边激子态波长较短,诱捕态波长较长.800nm激发与400nm激发时相比,激子态相对比重增加,这导致荧光峰的蓝移.We studied the steady-state and time-resolved luminescence properties of CdTe and CdTe/CdS core/shell quantum dots by one-and two-photon excitation with a femtosecond laser of low intensity. The 800 nm excitation causes a blue shift of the emission peak compared with 400 nm laser excitation. Near-quadratic laser power dependence of the up-conversion intensity and biexponential decay kinetics are observed. It is found that upconversion luminescence is composed of a photoinduced trapping and a band edge excitonic state. The blue shift of the emission peak is caused by the relative change in luminescence intensity between excitonic and trapping states. Two-step two-photon absorption involving the surface as intermediate states has been proposed for the mechanism of up-conversion luminescence of CdTe/CdS quantum dots.

关 键 词：CDTE量子点 CdTe/CdS核壳量子点 时间分辨荧光 上转换荧光 

分 类 号：O471.1[理学—半导体物理]