Evidence for the direct impact excitation of Mn centers in electroluminescent ZnS:Mn films

Tanaka, Shoto; Kobayashi, Hiroshi; Sasakura, Hiroshi; Hamakawa, Yoshihiro

doi:10.1063/1.322567

Cited by 71 publications

(14 citation statements)

References 10 publications

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“…[34] The weak emission bands (weak orange luminescence) centered at 578 (2.15 eV) and 582 nm (2.13 eV) are similar to those previously reported in PL studies of Mn 2+ -doped ZnS thin films in air. [35] As shown in Figure 10 (right, curves g and h), strong UV emission bands located at 345 (3.60 eV) and 326 nm (3.80 eV) have been observed for ZnS nanowires after removing the amine at 180°C for 48 and 96 h, respectively. These bands can be attributed to band-edge or excitonic emissions, as observed before for zinc blende ZnS quantum dots capped by mercaptoacetic acid, [36] and to the bandgap emission of bulk wurtzite ZnS (3.80 eV), respectively.…”

Section: Full Papermentioning

confidence: 82%

From Mesostructured Wurtzite ZnS‐Nanowire/Amine Nanocomposites to ZnS Nanowires Exhibiting Quantum Size Effects: A Mild‐Solution Chemistry Approach

Yao

2007

Adv Funct Materials

127

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Mesostructured wurtzite ZnS‐nanowire‐bundle/amine nanocomposites displaying remarkable quantum size effects are synthesized by using a mild‐solution reaction using different amines, such as n‐butylamine, ethylamine, and tetraethylenepentamine, Zn(NO3)2·6 H2O, and CS(NH2)2 or Na2S·9 H2O as the precursors at temperatures ranging from room temperature to 180 °C. A possible mechanism for the shape‐controlled growth of ZnS nanowires and nanocomposites is proposed. Increasing the reaction temperature or dispersing the composite in acetic acid or NaOH solution leads to the destruction of the periodic structure and the formation of individual wurtzite nanowires and their aggregates. The nanowire/amine composites and individual wurtzite nanowires both display obvious quantum size effects. Strong band‐edge emission is observed for the wurtzite ZnS nanowires after removal of the amine. The optical properties of these nanocomposites and nanowires are strongly related to the preparation conditions and can be finely tuned. This technique provides a unique approach for fabricating highly oriented wurtzite ZnS semiconductor nanowires, and can potentially be extended to other semiconducting systems.

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Section: Full Papermentioning

confidence: 82%

From Mesostructured Wurtzite ZnS‐Nanowire/Amine Nanocomposites to ZnS Nanowires Exhibiting Quantum Size Effects: A Mild‐Solution Chemistry Approach

Yao

2007

Adv Funct Materials

127

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“…The radiative rate constant k MnÀR is a function of the dipole matrix element between the 4 T 1 and 6 A 1 states of the Mn ion, [3,13,15,16] whereas k MnÀNR depends on the Mn environment and its local modes. [42][43][44][45] The wavefunction properties of the 4 T 1 and 6 A 1 states of the Mn ion are not much affected by its local environment, but its local modes are. Therefore, k MnÀNR is more likely the major factor that changes substantially with the Mn radial position in the core/shell nanocrystals.…”

Section: Pl and Epr Propertiesmentioning

confidence: 99%

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Yang

Chen

Angerhofer

et al. 2009

Chemistry A European J

108

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Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the radial position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals.This paper reports a study of the surface effects and position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (Phi(ET)) and the efficiency of the emission from the Mn ion (Phi(Mn)). Third, Phi(Mn) strongly depends on the radial position of Mn ions in the doped core/shell nanocrystals. The position-dependent changes of Phi(Mn) nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the Phi(Mn), the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that Phi(ET) depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Förster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.

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“…In the former case, the defect-related blue emission should be temporally observed besides the orange Mn 2+ emission since the electron-hole pairs generated by the impact-ionization of the host ZnS recombine via the defect-related states before the energy-transfer to the Mn 2+ ions [14]. On the other hand, in the latter case, only the orange Mn 2+ emission would be observed since the defect-related blue emission is inactive [14]. The former scheme is similar to the mechanism of PL emission after the generation of electron-hole pairs.…”

Section: Discussionmentioning

confidence: 99%

“…5 (a)), then the energy subsequently transfers to the Mn 2+ ions [15]. In the case of direct impact-excitation, the defect-related emission process is excluded [14]. As shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Orange electroluminescence from chemically synthesized zinc sulfide nanocrystals doped with manganese

Adachi

Morimoto

Hama

et al. 2008

Journal of Non-Crystalline Solids

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Evidence for the direct impact excitation of Mn centers in electroluminescent ZnS:Mn films

Cited by 71 publications

References 10 publications

From Mesostructured Wurtzite ZnS‐Nanowire/Amine Nanocomposites to ZnS Nanowires Exhibiting Quantum Size Effects: A Mild‐Solution Chemistry Approach

From Mesostructured Wurtzite ZnS‐Nanowire/Amine Nanocomposites to ZnS Nanowires Exhibiting Quantum Size Effects: A Mild‐Solution Chemistry Approach

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Orange electroluminescence from chemically synthesized zinc sulfide nanocrystals doped with manganese

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