Photoluminescence Properties of Manganese-Doped Zinc Selenide Quantum Dots

Abstract

Mn 2+ -doped II-VI semiconductor quantum dots reveal remarkably intense photoluminescence with a short lifetime associated with the 4 T 1 ( 4 G) f 6 A 1 ( 6 S) transition, which is spin-forbidden and is allowed because of crystal field effects. We explored the photophysical properties of high-quality, narrow-size-distribution Mn 2+doped ZnSe (ZnSe:Mn 2+ ) quantum dots. ZnSe:Mn 2+ quantum dots with varying amounts of dopant were studied at temperatures down to 10 K. Substitutional incorporation of Mn 2+ in ZnSe quantum dots was confirmed by electron paramagnetic resonance measurements as well. Photoluminescence emission (PL) and photoluminescence excitation (PLE) spectroscopies at low temperature were employed to examine the sp-d interactions. PL measurements of ZnSe:Mn 2+ quantum dots show Mn 2+ -related orange luminescence. PLE measurements were carried out at a fixed emission wavelength related to Mn 2+ orange luminescence. Five excited states corresponding to Mn 2+ d-d transitions were observed. The crystal field strength (10Dq) increases with increasing Mn 2+ concentration, increasing size, and decreasing temperature. In contrast to earlier conjectures about transition-metal-doped quantum dots, Mn 2+ -related photoluminescence feature could be observed in ZnSe:Mn 2+ quantum dots even when the excitation energy was lower than the forbidden gap but was equal to the energy of the d-d transitions. The behavior of ZnSe:Mn 2+ quantum dots was also compared with that of their bulk counterpart.

The aggregation of Fe3+ and their d–d radiative transitions in ZnSe:Fe3+ nanobelts by CVD growth

“…The competition between the near band edge and the Fe 3+ -related luminescence is apparent, in which the increasing Fe 3+ concentration lowers the intensity of the near band edge and the same situation has been observed in ZnSe:Mn QDs. 39 In addition, comparing to that observed for the low Fe 3+ concentration, the two peaks shown in Fig. 3(a) ions, which is in agreement with that reported for ZnSe:Mn nanoribbons.…”

Mn-Doped ZnSe Quantum Dots as Fluorimetric Mercury Sensor

“…Furthermore, the bandgap of Mn:ZnSe is blue-shifted with respect to undoped ZnSe QDs under the same experimental conditions, which reveal the formation of smaller-sized particles. This is consistent with the results by Mahamuni et al [55]. The synthesis process itself is affected by Mn additive.…”

“…This transition is spin-forbidden but is allowed because of crystal field effects [55]. Fang et al [54] notified that if the dopant ions are adsorbed on the surface of the host nanocrystal instead of being incorporated into its lattice, no dopant emission is observed and further the host emission is drastically quenched because a loosely adsorbed dopant ion can easily act as a surface trap that quenches the host PL [57].…”

Generation of white light from co-doped (Cu and Mn) ZnSe QDs

“…The observed red shift and blue shift in both cases were attributed to change in the reaction kinematics causing a subtle difference in the size of resultant QDs. [33,34] The optical absorption of Zn 1¡x¡y Cu x Mn y Se QDs shows a feature at 404 nm ( Figure 3) which is in between the Cu-and Mn-doped ZnSe QDs. This further confirms the formation of Zn 1¡x¡y Cu x Mn y Se QDs.…”

“…But in case of Cu incorporation in ZnSe, the increase in the band gap (by virtue of increase in size) is observed ( Figure 3). The change in the band gap is attributed to change in the reaction kinematics [15,33,34]; PLE measurements on such QDs will give a band edge at different positions (since the sizes are different). But if both the ions are present in the same QD, then the band-edge position should be the same.…”