Web Release Date: January 30,
Photoluminescence Properties of Manganese-Doped Zinc Selenide Quantum Dots
Department of Physics, University of Pune, Pune 411007, India
Received: August 27, 2007
In Final Form: October 29, 2007
Abstract:
Mn2+-doped II-VI semiconductor quantum dots reveal remarkably intense photoluminescence with a short
lifetime associated with the 4T1(4G) 
6A1(6S) transition, which is spin-forbidden and is allowed because of
crystal field effects. We explored the photophysical properties of high-quality, narrow-size-distribution Mn2+-doped ZnSe (ZnSe:Mn2+) quantum dots. ZnSe:Mn2+ quantum dots with varying amounts of dopant were
studied at temperatures down to 10 K. Substitutional incorporation of Mn2+ 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:Mn2+ quantum dots show Mn2+-related orange luminescence. PLE
measurements were carried out at a fixed emission wavelength related to Mn2+ orange luminescence. Five
excited states corresponding to Mn2+ d-d transitions were observed. The crystal field strength (10Dq) increases
with increasing Mn2+ concentration, increasing size, and decreasing temperature. In contrast to earlier
conjectures about transition-metal-doped quantum dots, Mn2+-related photoluminescence feature could be
observed in ZnSe:Mn2+ 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:Mn2+ quantum dots was also compared
with that of their bulk counterpart.
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