Local structures around Mn luminescent centers in Mn-doped nanocrystals of ZnS

Soo, Y. L.; Ming, Z. H.; Huang, S.; Kao, Y. H.; Bhargava, R. N.; Gallagher, D.

doi:10.1103/physrevb.50.7602

Cited by 192 publications

(109 citation statements)

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“…[9][10][11] Different types of Mn 2+ centers are present in nanocrystalline ZnS:Mn 2+ . 12,13 The orange luminescence originates from Mn 2+ ions on Zn 2+ sites, where the Mn 2+ is tetrahedrally coordinated by S 2-.…”

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Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺

et al. 2001

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The influence of the synthesis conditions on the properties of nanocrystalline ZnS:Mn 2+ is discussed. Different Mn 2+ precursors and different ratios of the precursor concentrations [S 2-]/[Zn 2+ ] were used. The type of Mn 2+ precursor does not have an effect on the luminescence properties in the synthesis method described. On going from an excess of [Zn 2+ ] to an excess of [S 2-] during the synthesis, the particle diameter increases from 3.7 to 5.1 nm, which is reflected by a change in the luminescence properties. Photoluminescence measurements also showed the absence of the ZnS defect luminescence around 450 nm when an excess [S 2-] is used during the synthesis. This effect is explained by the filling of sulfur vacancies. The ZnS luminescence is quenched with an activation energy of 62 meV, which is assigned to the detrapping of a bound hole from such a vacancy.Over the past few years, considerable interest in the novel optical and electrical properties of doped semiconductor nanocrystals (NC) has emerged. 1-5 These structures are interesting from a physical and chemical point of view mainly because several of their properties are very different from those of bulk materials. 3 Especially, the significant sizedependent shift in the band gap has attracted much attention. This so-called quantum-size effect allows one to tune the emission and excitation wavelengths of a nanocrystal by tuning the crystal radius r. A quite good first-order approximation to calculate the energy of the band gap is given by the Brus equation. 1 In the case of zinc blende ZnS, the bulk values of all the materials parameters are known. 6 For nanocrystalline ZnS this results in a relation between the particle radius r, in nanometers, and the band gap E, in electronvolts, as follows:Manganese-doped materials represent a class of phosphors that have already found their way into many applications. The 4 T 1 f 6 A 1 transition within the 3d 5 configuration of the divalent manganese ion (Mn 2+ ) has been studied extensively and its orange-yellow luminescence in ZnS is well documented. This luminescence was also observed in nanocrystalline ZnS:Mn 2+ 7,8 and applications have already been suggested. 9-11 Different types of Mn 2+ centers are present in nanocrystalline ZnS:Mn 2+ . 12,13 The orange luminescence originates from Mn 2+ ions on Zn 2+ sites, where the Mn 2+ is tetrahedrally coordinated by S 2-.Previous workers have always used equal concentrations of Zn 2+ and S 2-precursors in the synthesis of these ZnS: Mn 2+ nanocrystals. This letter will focus on the effect of the synthesis conditions on several properties of these nanocrystals. Two different Mn 2+ precursors were used and the influence of the ratio of [Zn 2+ ] to [S 2-] was investigated. The experimental comparison will include measurements of the diameter, reflectivity, temperature-dependent photoluminescence (PL) emission and excitation as well as luminescence lifetimes. From these results, new insights into the ZnS-related luminescence are obtained and a qualitative...

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Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺

et al. 2001

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“…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.…”

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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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“…13 The as a function of photoelectron momentum ͑k͒ was truncated and the curve of in between 3.0 and 11.0 Å −1 was then Fourier transformed to real ͑R͒ space for 14 To obtain quantitative local structural information, an improved curve-fitting procedure was employed to fit Fourier-filtered functions in k-space 15,16 with theoretical backscattering amplitude and phase-shift functions calculated by the well-known FEFF EXAFS simulation program. 17 The local structural parameters determined by curve fittings are listed in Tables I.…”

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confidence: 99%

Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

Soo

Chen

Huang

et al. 2008

Journal of Applied Physics

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Local environment surrounding Zr atoms in the thin films of nanocrystalline zirconia ͑ZrO 2 ͒ has been investigated by using the extended x-ray absorption fine structure ͑EXAFS͒ technique. These films prepared by the ion beam assisted deposition exhibit long-range structural order of cubic phase and high hardness at room temperature without chemical stabilizers. The local structure around Zr probed by EXAFS indicates a cubic Zr sublattice with O atoms located on the nearest tetragonal sites with respect to the Zr central atoms, as well as highly disordered locations. Similar Zr local structure was also found in a ZrO 2 nanocrystal sample prepared by a sol-gel method. Variations in local structures due to thermal annealing were observed and analyzed. Most importantly, our x-ray results provide direct experimental evidence for the existence of oxygen vacancies arising from local disorder and distortion of the oxygen sublattice in nanocrystalline ZrO 2 . These oxygen vacancies are regarded as the essential stabilizing factor for the nanostructurally stabilized cubic zirconia.

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Local structures around Mn luminescent centers in Mn-doped nanocrystals of ZnS

Cited by 192 publications

References 8 publications

Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺

Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺

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

Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

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Local structures around Mn luminescent centers in Mn-doped nanocrystals of ZnS

Cited by 192 publications

References 8 publications

Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn2+

Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn2+

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

Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

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Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺

Synthesis and Photoluminescence of Nanocrystalline ZnS:Mn²⁺