Electronic Properties of Surface Vacancies in CdS Nanocrystals

Kupchak, I. M.; Serpak, N. F.; Kapush, O.A.; Korbutyak, D. V.

doi:10.15330/pcss.19.1.34-39

Cited by 3 publications

(2 citation statements)

References 30 publications

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“…As it was described in [10] and discussed above, PL spectra of Cd 1-x Zn x S QDs show the bands, which are obviously related with the presence of surface defects. Particularly, the most probable kind of defects in CdS QDs, responsible for the luminescence, is the cadmium vacancy [9]. Taking it into account, we study here electronic and atomic structure of CdS, ZnS and Cd 1-x Zn x S QDs, containing metal vacancies V Cd , V Zn .…”

Section: Resultsmentioning

confidence: 99%

“…The nature of these localized states often remains uncertained, because of the large number of possible kinds of defects in both of QD and its surrounding. Particularly, there are a series of articles [3][4][5][6][7][8][9], devoted to studying the PL properties and ascertaining the possible mechanism of radiative recombination in CdS QDs, where the cadmium vacancy is defined as the most probable channel of luminescence.…”

Section: Introductionmentioning

confidence: 99%

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Metal vacancies in Cd1-xZnxS quantum dots

Kupchak¹,

Korbutyak²,

Serpak³

et al. 2020

Semicond. phys. quantum electron. and optoelectron.

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Structural and electronic characteristics of metal vacancies in nanocrystals Cd 1-x Zn x S have been studied within the density functional method. The electron state density and vacancy formation energy have been calculated, and an analysis of structural relaxation has been performed. With these theoretical findings and available experimental data, we have concluded that the vacancies of cadmium are the possible centers of radiative recombination in these structures.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metal vacancies in Cd1-xZnxS quantum dots

Kupchak¹,

Korbutyak²,

Serpak³

et al. 2020

Semicond. phys. quantum electron. and optoelectron.

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View full text Add to dashboard Cite

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Electronic characteristics of CdS quantum dots with defects

2020

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Using the density functional theory and the generalized gradient approximation, we calculated the atomic structure, the density of electronic states, and the optical absorption spectra of CdS quantum dots containing intrinsic defects — a cadmium vacancy VCd and an interstitial sulfur atom SI, and substitutional impurities — zinc and copper in place of the atom cadmium — ZnCd and CuCd, respectively. The calculations were performed for the Cd33S33 cluster corresponding to the so-called “magic” size of the quantum dot. This size has a minimum of dangling bonds at the surface and allows the using of such a cluster without the passivation. The structural relaxation during the formation of such defects and the distribution of the wave function of the state corresponding to the top of the valence band are analyzed in details. It has been shown that the cadmium vacancy forms local states in the band gap of CdS nanocrystals, and can serve as centers of radiative recombination. Other defects form energy levels in the depths of the valence band or near its top, but whose energy positions do not correspond to the band maxima in the experimental photoluminescence spectra of CdS quantum dots, both undoped and doped with zinc. The calculated optical absorption spectra demonstrate a strong peak in the region of fundamental absorption of CdS for a cluster containing a substitutional impurity of CuCd, in contrast to other systems where no such peaks are observed. In addition, the replacement of the cadmium atom with copper leads to a decrease in the number of chemical bonds to three and, accordingly, to the largest relaxation among the systems studied. This feature is caused by the crystal structure inhomogeneity of copper sulfide CuxS, which, depending on stoichiometry, can be either a semiconductor or a metal.

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Surface Luminescence of A2b6 Semiconductor Quantum Dots (Review)

Korbutyak¹

2021

Optoelektron. napìvprovìd. teh.

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Semiconductor zero-dimensional nanocrystals – quantum dots (QDs) – have been increasingly used in various fields of opto- and nanoelectronics in recent decades. This is because of the exciton nature of their luminescence, which can be controlled via the well known quantum-dimensional effect. At the same time, at small nanocrystall sizes, the influence of the surface on the optical and structural properties of nanocrystals increases significantly. The presence of broken bonds of surface atoms and point defects – vacancies and interstial atoms – can both weaken the exciton luminescence and create new effective channels of radiant luminescence. In some cases, these surface luminescence becomes dominant, leading to optical spectra broadening up to the quasi-white light. The nature of such localized states often remains unestablished due to the large number of the possible sorts of defects in both of QD and its surrounding. In contrast to exciton luminescence, which can be properly described within effective-mass approximations, the optical properties of defects relay on chemical nature of both defect itsself and its surrounding, what cannot be provided by “hydrogen-type coulomb defect” approximation. Moreover, charge state and related to this lattice relaxation must be taken into account, what requires an application of atomistic approach, such as Density functioal theory (DFT). Therefore, this review is devoted to the study of surface (defect) states and related luminescence, as well as the analysis of possible defects in nanocrystals of semiconductor compounds A2B6 (CdS, CdZnS, ZnS), responsible for luminescence processes, within ab initio approach. The review presents the results of the authors' and literature sources devoted to the study of the luminescent characteristics of ultra-small (<2 nm) QDs.

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Electronic Properties of Surface Vacancies in CdS Nanocrystals

Cited by 3 publications

References 30 publications

Metal vacancies in Cd1-xZnxS quantum dots

Metal vacancies in Cd1-xZnxS quantum dots

Electronic characteristics of CdS quantum dots with defects

Surface Luminescence of A2b6 Semiconductor Quantum Dots (Review)

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