Electronic structure of Mn-doped ZnS nanocrystals

Albe, V.; Jouanin, C.; Bertho, D.

doi:10.1103/physrevb.57.8778

Cited by 27 publications

(14 citation statements)

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“…Their properties which depend on size [1][2][3][4][5] and shape 3 have overimposed effects due to quantum confinement. For instance, when the QD radius is smaller than the Bohr radius of exciton, quantum-confinement effects appear, such as the blue shift of gaps and the discretization of energy spectra [1][2][3][4][5][6] . The gap properties can also be tuned intentionally with doping [6][7][8][9][10][11][12][13] .…”

Section: Introductionmentioning

confidence: 99%

“…For instance, when the QD radius is smaller than the Bohr radius of exciton, quantum-confinement effects appear, such as the blue shift of gaps and the discretization of energy spectra [1][2][3][4][5][6] . The gap properties can also be tuned intentionally with doping [6][7][8][9][10][11][12][13] . Recently, much effort has focused on II-VI semiconductor NCs doped with magnetic impurities such as Mn, which is the topic of this work.…”

Section: Introductionmentioning

confidence: 99%

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First-principles calculations of the magnetic properties of (Cd,Mn)Te nanocrystals

2009

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We investigate the electronic and magnetic properties of Mn-doped CdTe nanocrystals (NCs) with ∼ 2 nm in diameter which can be experimentally synthesized with Mn atoms inside. Using the density functional theory, we consider two doping cases: NCs containing one or two Mn impurities. Although the Mn d peaks carry five up electrons in the dot, the local magnetic moment on the Mn site is 4.65 µB. It is smaller than 5 µB because of the sp-d hybridization between the localized 3d electrons of the Mn atoms and the s-and p-type valence states of the host compound. The sp-d hybridization induces small magnetic moments on the Mn nearest-neighbor Te sites, antiparallel to Mn moment affecting the p-type valence states of the undoped dot, as usual for a kinetic mediated exchange magnetic coupling. Furthermore, we calculate the parameters standing for the sp-d exchange interactions: Conduction N0α and valence N0β are close to the experimental bulk values when the Mn impurities occupy bulk-like NCs' central positions, and they tend to zero close to the surface. This behavior is further explained by an analysis of valence band-edge states showing that symmetry breaking splits the states and in consequence reduces the exchange. For two Mn atoms in several positions, the valence edge states show a further departure from an interpretation based in a perturbative treatment. We also calculate the d-d exchange interactions |J dd | between Mn spins. The largest |J dd | value is also for Mn atoms on bulk-like central sites; in comparison with the experimental d-d exchange constant in bulk Cd0.95Mn0.05Te it is four times smaller.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First-principles calculations of the magnetic properties of (Cd,Mn)Te nanocrystals

2009

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“…Very recently, D. Norris et al [13] reported obtaining high quality ZnSe colloidal nanocrystals doped with single Mn 2+ impurities. Also, several different groups have proposed models to try to explain the processes occuring with the impurity centers inside the confined nanocrystals [6,[14][15]. But while it is now well established that the confinement effect strongly modifies the electronic structure of nanocrystals, the effects of the confinement on the energy structure and transitions of the Mn impurity in the nanocrystals, still are controversial.…”

Section: Iintroductionmentioning

confidence: 99%

“…In contrast to undoped materials, the impurity states in a doped nanocrystal play an important role in the electronic structure, transition probabilities and the optical properties. In recent years, attempts to understand more about these zero-dimensional nanocrystal effects have been made in several labs by doping an impurity in a nanocrystal, searching for novel materials and new properties, and among them Mn-doped ZnS nanoparticles have been intensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Among many bulk wide band gap compounds, manganese is well known as an activator for photoluminescence (PL) and electroluminescence (EL) and the Mn 2+ ion d-electrons states act as efficient luminescent centers while doped into a semiconductors.…”

Section: Introductionmentioning

confidence: 99%

Theory of luminescent emission in nanocrystal ZnS:Mn with an extra electron

Huong

Birman

2004

Phys. Rev. B

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We consider the effect of an extra electron in a doped quantum dot ZnS : M n 2+ . The Coulomb interaction and exchange interaction between the extra electron and the states of the Mn ion will mix the wavefunctions, split the impurity energy levels, break the previous selection rules and change the transition probabilities. Using this model of an extra electron in the doped quantum dot, we calculate the energy and the wave functions, the luminescence efficiency and the transition lifetime and compare with the experiments. Our calculation shows that two orders of magnitude of lifetime shortening can occur in the transition 4 T 1 − 6 A 1 , when an extra electron is present.PACS numbers: 73.20. Dx, 78.60.J, 42.65, 71.35 1 I.Introduction. In contrast to undoped materials, the impurity states in a doped nanocrystal play an important role in the electronic structure, transition probabilities and the optical properties. In recent years, attempts to understand more about these zero-dimensional nanocrystal effects have been made in several labs by doping an impurity in a nanocrystal, searching for novel materials and new properties, and among them Mn-doped ZnS nanoparticles have been intensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Among many bulk wide band gap compounds, manganese is well known as an activator for photoluminescence (PL) and electroluminescence (EL) and the Mn 2+ ion d-electrons states act as efficient luminescent centers while doped into a semiconductors.In 1994 Bhargava and Gallagher [1,2] reported the first realization of a ZnS semiconductor nanocrystal doped with Mn isoelectronic impurities and claimed that Mn-doped ZnS nanocrystal can yield both high luminescence efficiency and significant lifetime shortening. The yellow emission characterized for Mn 2+ in bulk ZnS [16][17][18], which is associated with the transition 4 T 1 − 6 A 1 , was reported to be observed in photoluminescence (PL) spectra for the Mn 2+ in nanocrystal ZnS. In nanocrystals, however, the PL peak for the yellow emission is reported slightly shifted toward a lower energy (in bulk ZnS:Mn it peaks arount 2.12 ev, in nanocrystal ZnS:Mn it peaks at 2.10 eV). Also, the reported linewidth of the yellow emision in the PL spectrum for a nanocrystal is larger than for the bulk. Most strikingly, the luminescence lifetime of the Mn 2+ 4 T 1 − 6 A 1 transition was reported to decrease by 5 orders of magnitude, from 1.8 ms in bulk to 3.7 ns and 20.5 ns in nanocrystals while maintaining the high (18%) quantum efficiency.In ref.[6] the authors suggested that the increase in quantum efficiency as well as the lifetime shortening is the result of strong hybridization of s-p electrons of the ZnS host and d-electrons of the Mn impurity due to confinement, and also of the modification of the crystal field near the surface of the nanocrystals. Stimulated by this dramatic result, many other laboratories are trying to synthesize the Mn-doped ZnS nanocrystals and considerable attention has been paid to optical properties o...

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“…The typical phenomena appearing in quantum dots are the discretization of the electronic spectra and the blueshift of the fundamental gaps. [5][6][7][8][9][10][11] Moreover, the GaN nanocrystals can be doped with diluted magnetic impurities such as manganese. In fact, Ref.…”

Section: Introductionmentioning

confidence: 99%

Antiferromagnetic order in (Ga,Mn)N nanocrystals: A density functional theory study

2010

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We investigate the electronic and magnetic properties of ͑Ga,Mn͒N nanocrystals using the density functional theory. We study both wurtzite and zinc-blende structures doped with one or two substitutional Mn impurities. For a single Mn dopant placed close to surface, the behavior of the empty Mn-induced state, hereafter referred to as "Mn hole," is different from bulk ͑Ga,Mn͒N. The energy level corresponding to this off-center Mn hole lies within the quantum-dot gap near the conduction edge. For two Mn dopants, the most stable magnetic configuration is antiferromagnetic and this result was unexpected since ͑Ga,Mn͒N bulk shows ferromagnetism in the ground state. The surprising antiferromagnetic alignment of two Mn spins is ascribed also to the holes linked to the Mn impurities that approach the surface. Unlike ͑Ga,Mn͒N bulk, these Mn holes in confined ͑Ga,Mn͒N nanostructures do not contribute to the ferromagnetic alignment of the two Mn spins.

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Electronic structure of Mn-doped ZnS nanocrystals

Cited by 27 publications

References 14 publications

First-principles calculations of the magnetic properties of (Cd,Mn)Te nanocrystals

First-principles calculations of the magnetic properties of (Cd,Mn)Te nanocrystals

Theory of luminescent emission in nanocrystal ZnS:Mn with an extra electron

Antiferromagnetic order in (Ga,Mn)N nanocrystals: A density functional theory study

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