High Density Suspension of Semiconductor Nanocrystals in Matrices and Their Coherent Cooperative Phenomena among Electronic Excited States

半导体纳米晶在基质中的高密度悬浮及其电子激发态的相干协同现象

基本信息

批准号：
07404014
负责人：
ITOH Tadashi
金额：
$ 23.55万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

The aim of this project is to investigate the optical properties of excitons confined in semiconductor nanocrystals together with exciton internal structures, to clarify the mutual interaction among excitons in one nanocrystal, and also to study cooperative phenomena of coherent excitons between nanocrystals both in experiment and theory.1) By means of ion beam sputtering method, we have made CdSe nanocrystals suspended in metrices with high density and also made CdSe, ZnSe and ZnO ultrathin films. We have got the quality of films by X ray diffraction and AFM topography, and the reduction of crystal defects by optical measurement.2) Optical investigation of confined exciton statesa) Picosecond time-resolved luminescence measurement has been perfomed under two-photon resonant excitation. We have measured the size dependence of the ratio between resonant luminescence and resonant scattering and proposed the optical non-Markov processes inherent in nanocrystals.b) By means of single-dot m … More icrospectroscopy of CuCl and ZnCdSe quantum dots, we have succeeded to observe the narrowing, blinking and photofatigue phenomena of exciton luminescence. We have found that the energy of the second lowest confined exciton state is considerably different from that expected for simple exciton confinement model and suggested the possibility of dipole self interaction effect on p-type confined states.c) In CuCl nanocrystals suspended in polymer at high density, we have found a peculiar phenomenon of luminescence enhancement under ultraviolet laser irradiation. Similar to the case of porous Si, photoionization or photo-induced change of surface structure has been considered to play an important role in this phenomenon.d) The optical transition between Rydberg 1S to 2P exciton states has been measured by means of infrared transient spectroscopy. As the size of nanocrystals decreases, the confinement of the 2P exciton deviates from the model of the confinement of exciton translational motion. Theoretical spectra calculated for the 1S to 2P transition is found to coincide qualitatively with the experimental ones.From these results, a progress in the study of confined excitons has been achieved both in experiment and theory and one can expect a possibility of studying the cooperative phenomena of coherent excitons. Less

该项目的目的是调查限制在半导体纳米晶体中的激子的光学特性以及令人兴奋的内部结构，以阐明一种纳米晶体中激子之间的激子之间的相互作用，也可以通过在实验和理论中进行纳米晶体之间的纳米晶体之间的相干激体的合作现象。高密度的指标，还制作了CDSE，ZnSE和ZnO Ultrathin膜。我们通过X射线衍射和AFM地形获得了薄膜的质量，并通过光学测量减少了晶体缺陷。2）在两光子谐振兴奋下，在两光弹性的兴奋下培养了Picsecond Interned State的光学投资。我们已经通过单点m的含量固有的光发光和谐振散射之间的大小依赖性，并提出了纳米晶体中固有的光学非马尔科夫过程。我们发现，第二低约束兴奋状态的能量被认为与对简单令人兴奋的模型的期望不同，并提出了偶极子自我相互作用对P型限制状态的可能性。与多孔SI的情况相似，在这种现象中，光电离世或光诱导的表面结构变化都起着重要作用。d）Rydberg 1s 1s到2p刺激状态之间的光学转变已通过红外瞬态光谱法测量。随着纳米晶体的大小减小，2P令人兴奋的隔离与激发转化运动的限制模型。发现针对1S至2P转变计算的理论光谱与实验性谱相吻合。从这些结果中，在实验和理论中已经取得了狭窄的激子研究的进展，人们可以期望研究对照激子的合作现象。较少的