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CdSe / ZnS semiconductor quantum dot electronic structure theory research

Author: ZhangJianXiang
Tutor: HeQingLi
School: Northwestern University
Course: Optics
Keywords: CdSe quantum dots electronic structure Tight-binging model effective-mass approximation Exciton model
CLC: O471.1
Type: Master's thesis
Year: 2009
Downloads: 257
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Abstract


Recent years, semiconductor quantum dots (QDs) are widely used in scientific research and have been paid more and more attention. A great improvement in the research of semiconductor quantum dots has been made in both theory and experiment. However, the structure of QDs is very complicated, so electronic structure and optical property of QDs are not very clear now. This problem should be further researched. This paper puts its point on the electronic structure of CdSe/ZnS QDs and provides the theoretical basis for the further research of QDs’ optical property and application.Firstly, the electronic structure of QDs is calculated using a tight-binding method. First of all, the Schr(o|¨)dinger equation of electrons of the core CdSe is built. From the solution of the equation, there exist a critical radius of electrons in the core CdSe, so does in the holes. According to the difference of the two radii, we divide the quantum confinement effect into three regimes: weak confinement regime, intermediate confinement regime and strong confinement regime. Next, know electron energy bands of the core CdSe. A tight-binding model is developed, so band structures of CdSe quantum dots and CdSe crystals are calculated respectively with data in the references. Finally, the energy level division and emission spectrum getting narrow are explained by discussing the outcome of the model.Secondly, the exciton energy level of CdSe/ZnS QDs is calculated using effective-mass approximation method. The exciton model of QDs is also built. We suppose a spheral surface and an infinitude potential well to work out the QDs energy level in the three types of confinement regime mentioned above. So does the relation between energy level and the radii, to illustrate an increase of the energy level caused by the decrease of the QDs radii.Thirdly, we discuss several luminescence routes and main factors that affect the QDs spectrum (such as power, QDs radii distribution, environment and so on). As the environment may have an effect on the QDs’ optical property. So, more work will be done in order to get the the characteristic of the QDs’ luminescence. And further work is expected in the end.

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CLC: > Mathematical sciences and chemical > Physics > Semiconductor physics > Semiconductive Theory > Semiconductor quantum theory
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