Magnetic circular dichroism spectroscopy of Co<sup>2+</sup>:CdS diluted magnetic semiconductor quantum dots

Radovanovic, Pavle R.; Gamelin, Daniel R.

doi:10.1117/12.453784

Cited by 6 publications

(4 citation statements)

References 24 publications

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“…MCD is useful for its sensitivity to site-specific metal contributions in a given material . MCD has been previously used to elucidate fine structures that may appear in optical features such as band gap absorption edges in semiconductors, intra-atomic transitions, and LSPRs. − The MCD spectra are plotted as the difference spectra (Δ A ) of left circularly polarized light (LCP) absorption subtracted from right circularly polarized light (RCP) absorption, where LCP is selective for Δ M J = + 1 while RCP is selective for Δ M J = – 1.…”

Section: Resultsmentioning

confidence: 99%

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals

et al. 2022

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The impact of a magneto-structural phase transition on the carrier effective mass in Cu5FeS4 plasmonic semiconductor nanocrystals was examined using magnetic circular dichroism (MCD). Through MCD, the sample was confirmed as p-type with variable-temperature studies from 1.8–75 K. Magnetic field-dependent behavior is observed, showing an asymptotic behavior at high field with an m* value 5.98 m*/m e at 10 T and 2.73 m*/m e at 2 T. Experimentally obtained results are holistically compared to SQUID magnetization data and DFT calculations, highlighting a dependency on vacancy-driven polaronic coupling, magnetocrystalline anisotropy, and plasmon coupling of the magnetic field, all contributing to an overall decrease in the hole mean free path dependent on the magnetic field applied to Cu5FeS4.

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Section: Resultsmentioning

confidence: 99%

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals

et al. 2022

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“…Semiconductor nanocrystals, as a class of luminescent chromophores, are important in the growing fields of nanoscience and nanotechnology. − In spherical dots, band gaps and oscillator strengths can be tuned by variation of the diameter while for quantum rod and tubes by the radii and lengths. − The incorporation of transition metal (TM) magnetic impurities into a semiconductor lattice can control photoconductivity, alter optical, and change magnetic properties of nanocrystals. TM dopants can be efficient in photovoltaic energy conversion, − nanospintronics and spin-photonics, magneto optical and magneto-electronic properties, − , and the giant Zeeman effect . Photoluminescence properties become unusual if nanocrystals are doped by Mn atoms.…”

Section: Introductionmentioning

confidence: 99%

“…35−37 The incorporation of transition metal (TM) magnetic impurities into a semiconductor lattice can control photoconductivity, alter optical, and change magnetic properties of nanocrystals. TM dopants can be efficient in photovoltaic energy conversion, 38−42 nanospintronics and spinphotonics, 43 magneto optical and magneto-electronic properties, [44][45][46][47][48][49][50][51][52]54 and the giant Zeeman effect. 55 Photoluminescence properties become unusual if nanocrystals are doped by Mn atoms.…”

Section: Introductionmentioning

confidence: 99%

Tunable Luminescence in CdSe Quantum Dots Doped by Mn Impurities

Proshchenko

Dahnovsky

2014

J. Phys. Chem. C

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In this work, we study the effect of a dual luminescence for CdSe quantum dots (QDs) doped by a manganese impurity. In this effect, one line has fast relaxation and corresponds to light emission from CdSe conduction band, whereas the second is very slow in relaxation with the relaxation time of 0.1−1.0 ms. The second line disappears for quantum dots (QDs) with diameters D ≥ 3.3 nm, and therefore, the luminescence becomes tunable by a QD size. The problem is computationally challenging because of large size QDs and a high degeneracy of the energy states. To overcome this problem, we make four assumptions. These assumptions are the following: (1) a QD optical gap is independent of an Mn impurity for small concentrations; (2) we combine electronic structure calculations for medium size CdSe QDs with the effective mass calculations for medium and large QD sizes and match them in the medium size region, assuming that based on assumption 1, the optical spectrum is independent of Mn even for larger QDs; (3) we cut an MnSe 4 fragment out of the middle of Cd 23 Mn 1 Se 24 , Cd 31 Mn 1 Se 32 , and Cd 81 Mn 1 Se 82 QDs and check whether we can quantitatively explain the mechanism of the second, slow relaxation emission in these experiments using the ab initio SAC−CI multiconfiguration method; and (4) the slow luminescence line is independent of a QD size. We have proved theoretically all these assumptions and found that the critical size of a quantum dot, the size when the second luminescence line disappears, is 3.2 nm, and the slow luminescence energy is 2.3 eV in a tetrahedral ligand field. We also study the case for an Mn impurity placed at a QD surface. Then the symmetry of a fragment is C 3v , and the results of the calculations reveal that the slow luminescence energy is 2.47 eV with the critical size D = 2.7 nm, instead of 3.2 nm for a tetrahedral ligand field. We also predict how this energy depends on the length of an Mn−Se bond. The dependencies appear to be the opposite in these two cases. For the tetrahedral symmetry, the luminescence energy grows with the bond length, whereas for the pyramid, C 3v , symmetry (an Mn is at the surface), it goes down. Furthermore, we study a luminescence energy dependence on a Se−Mn−Se pyramid angle. We find that it is angle independent. These results could be useful for CdSe nanocrystal structures different than Wurtzite.

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“…These results are in agreement with previous literature reports on tetrahedrally coordinated Co 2+ ions in molecular complexes 70 and Co 2+ -doped nanocrystals. 56 MCD spectroscopy can also be used to investigate the sp-d exchange interaction between the magnetic dopants and the charge carriers of the host lattice, i.e., to probe the magneto-optical activity of excited states of excitonic nature. In the case of the sp-d exchange interaction, the energy splitting between the excited states in a magnetic field is expected to be significantly larger than the intrinsic Zeeman splitting present in undoped materials, thus leading to its denomination as giant Zeeman splitting.…”

Section: Resultsmentioning

confidence: 99%

Impurity incorporation and exchange interactions in Co2+-doped CdSe/CdS core/shell nanoplatelets

Fainblat

Delikanlı

Spee

et al. 2019

The Journal of Chemical Physics

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The intentional incorporation of transition metal impurities into colloidal semiconductor nanocrystals allows an extension of the host material's functionality. While dopant incorporation has been extensively investigated in zero-dimensional quantum dots, the substitutional replacement of atoms in two-dimensional (2D) nanostructures by magnetic dopants has been reported only recently. Here, we demonstrate the successful incorporation of Co 2+ ions into the shell of CdSe/CdS core/shell nanoplatelets, using these ions (i) as microscopic probes for gaining distinct structural insights and (ii) to enhance the magneto-optical functionality of the host material. Analyzing interatomic Co 2+ ligand field transitions, we conclude that Co 2+ is incorporated into lattice sites of the CdS shell, and effects such as diffusion of dopants into the CdSe core or diffusion of the dopants out of the heterostructure causing self-purification play a minor role. Taking advantage of the absorption-based technique of magnetic circular dichroism, we directly prove the presence of sp-d exchange interactions between the dopants and the band charge carriers in CdSe/Co 2+ :CdS heteronanoplatelets. Thus, our study not only demonstrates magneto-optical functionality in 2D nanocrystals by Co 2+ doping but also shows that a careful choice of the dopant type paves the way for a more detailed understanding of the impurity incorporation process into these novel 2D colloidal materials.Published under license by AIP Publishing. https://doi. ARTICLEscitation.org/journal/jcp 76 J. A. Gaj and J. Kossut, "Basic consequences of sp-d and d-d interactions in

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Magnetic circular dichroism spectroscopy of Co²⁺:CdS diluted magnetic semiconductor quantum dots

Cited by 6 publications

References 24 publications

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals

Tunable Luminescence in CdSe Quantum Dots Doped by Mn Impurities

Impurity incorporation and exchange interactions in Co2+-doped CdSe/CdS core/shell nanoplatelets

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Magnetic circular dichroism spectroscopy of Co2+:CdS diluted magnetic semiconductor quantum dots

Cited by 6 publications

References 24 publications

Effective Mass for Holes in Paramagnetic, Plasmonic Cu5FeS4 Semiconductor Nanocrystals

Effective Mass for Holes in Paramagnetic, Plasmonic Cu5FeS4 Semiconductor Nanocrystals

Tunable Luminescence in CdSe Quantum Dots Doped by Mn Impurities

Impurity incorporation and exchange interactions in Co2+-doped CdSe/CdS core/shell nanoplatelets

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Magnetic circular dichroism spectroscopy of Co²⁺:CdS diluted magnetic semiconductor quantum dots

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals

Effective Mass for Holes in Paramagnetic, Plasmonic Cu₅FeS₄ Semiconductor Nanocrystals