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The Mechanism of Photo-electricity Properties for the Passivation of GroupⅣ-ⅥQuantum Dots

Author: XiongWei
Tutor: BiGang
School: Zhejiang University
Course: Physical Electronics
Keywords: Density Functional Theory(DFT) quantum dots passivation photoelectricity properties
CLC: TN304.24
Type: Master's thesis
Year: 2012
Downloads: 76
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Abstract


Semiconductor quantum dots(QDs) materials have been paid attention widely because of their special physical porperties. Where, Group IV-VI QDs based on PbSe、PbS、PbTe have been the hot point in research due to their potential applicability(For example, solar energy battery, photoelectric detector and laser). Although a great improvement in the research of semiconductor quantum dots materials has been made in both theory and experiment, the properties of passivated quantum dots is not clear and need to be further studied. This paper mainly puts its point on the energy structure and the density of state of group IV-VI QDs, provides the theoretical basis for the further research of QDs’optical and electronic properties and application.Firstly, the basic frame and the developing process of Density Functional Theory (DFT) is introduced. We begin to illustrate Thomas-Fermi model, Hohenberg-Kohn theorem, Kohn-Sham equation and the recent various correction of DFT include of Generalized Gradient Approximation (GGA) and Local Density Approximations (LDA). After that, we introduce the simulation software-MS and FDTD solution in this paper simply.Secondly, this paper study different structure and different size cluster through the calculation of DFT and we obtain the lowest energy structure of stoichiometric PbSe cluster. Besides, we calculate binding energy, average bond length, band gap, band structure, density of state, the highest occupied molecular orbit (HOMO), the lowest unoccupied molecular orbit (LUMO) in each cluster and so on. Then we obtain the discipline of changing in a variety of properties with the increase of the atomic numbers n by comparing and analyzing. Then, this paper calculate the extinction spectrum of sphere QDs including PbSe, PbS, PbTe by the software FDTD Solution.Thirdly, the PbSe QDs is passivated by the six materials of H, O, N, Cl, Br, F (ligand) and binding energy, average bond length, band gap, band structure and density of state in the passivated PbSe QDs are calculated. The surface of QDs is supposed to be sphere and the potential of surface is supposed to be infinitude potential. The four types of QDs include Pb1Se6, Pb6Se1, Pb6Se13, Pb13Se6 is passivated by three materials of H, O, N, Cl, Br, F. Then, the the effect of passivation in the six materials of H, O, N, Cl, Br, F have been analyzed and compared.At the last section of paper, the work is summarized and the follow-up work is out looked.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Semiconductor technology > General issues > Material > Compound semiconductor > Ⅳ - Ⅵ compound semiconductors
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