Electronic and optical properties of CdS/CdZnS nanocrystals

doi:10.1088/1674-1056/21/8/087302

摘要/Abstract

摘要： Cd_1-xZn_xS nanocrystals are prepared by co-precipitation method with different atomic fractions of Zn and their textures, structural transformations, and optical properties with increasing x value in Cd_1-xZn_xS are studied from scanning electron micrograph, electron diffraction pattern, and absorption spectra respectively. Quantum confinement in a strained CdS/Cd_1-xZn_xS related nanodot with various Zn content values is investigated theoretically. Binding energies on exciton bound CdS/Cd_xZn_1-xS quantum dot are computed, considering the internal electric field induced by the spontaneous and piezoelectric polarizations and thereby interband emission energy is calculated as a function of dot radius. The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically. Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm. X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with the increase of Zn content. The lattice constant gradually decreases as Zn content increases. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as Zn content increases. The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for CdS film and 3.5 eV for ZnS film. Our numerical results are in good agreement with the experimental results.

关键词: quantum dots, quasicrystals, semiconductor

Abstract: Cd_1-xZn_xS nanocrystals are prepared by co-precipitation method with different atomic fractions of Zn and their textures, structural transformations, and optical properties with increasing x value in Cd_1-xZn_xS are studied from scanning electron micrograph, electron diffraction pattern, and absorption spectra respectively. Quantum confinement in a strained CdS/Cd_1-xZn_xS related nanodot with various Zn content values is investigated theoretically. Binding energies on exciton bound CdS/Cd_xZn_1-xS quantum dot are computed, considering the internal electric field induced by the spontaneous and piezoelectric polarizations and thereby interband emission energy is calculated as a function of dot radius. The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically. Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm. X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with the increase of Zn content. The lattice constant gradually decreases as Zn content increases. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as Zn content increases. The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for CdS film and 3.5 eV for ZnS film. Our numerical results are in good agreement with the experimental results.

Key words: quantum dots, quasicrystals, semiconductor

中图分类号: (Quantum wells)

73.21.Fg

71.55.-i (Impurity and defect levels)

A. John Peter, Chang Woo Lee. Electronic and optical properties of CdS/CdZnS nanocrystals[J]. 中国物理B, 2012, 21(8): 87302-087302.

A. John Peter, Chang Woo Lee. Electronic and optical properties of CdS/CdZnS nanocrystals[J]. Chin. Phys. B, 2012, 21(8): 87302-087302.

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