二六族核殼結構量子點之光學特性研究

Abstract

In this thesis we report two studies include optical properties of CdTe/CdSe core-shell type II quantum dots and time-resolved photoluminescence (PL) in CdSe/ZnS core-shell type I quantum dots. The former and later results are obtained from photoluminescence, photoluminescence excitation measurement and time-resolved PL measurement respectively. Quite interesting results provide useful results for the enhancement of our understanding and application in these materials. I.Optical properties of CdTe/CdSe core-shell type II quantum dots We report investigation of optical properties of type-II CdTe/CdSe core-shell quantum dots. Several peculiar behaviors different from those of type I band alignment have been observed. In the measurement of power dependence of PL, we observe that the peak energy increases with the third root of excitation intensity. The integrated PL intensity varies with excitation intensity as a linear relation. These observation can be interpreted in terms of the band bending effect due to the spatially phoexcited carriers in a type-II band alignment. In addition, we get the exciton binding energy about 17.5 meV, which is much larger than that of quantum wells, but comparable with the theoretical prediction of the exciton energy of quantum dots. II.Relaxation dynamics of luminescence in CdSe/ZnS core-shell type I quantum dots We report investigation of PL dynamics of CdSe/ZnS core-shell type-I quantum dots. The PL intensity shows a biexponential decay behavior, which has been observed. We find that the radiactive recombination processes consist of a fast decay (~1 ns) and slow decay component (~10 ns). Due to the photon energy and temperature dependence of decay time experiments, we suggest that the fast and slow decay times involve recombination process of the photoinduced charged exciton and the band edge excitons.