Fluorescence lifetime of Mn-doped ZnSe quantum dots with size dependence

Radiative lifetimes of high quality Mn:ZnSe nanocrystals synthesized by nucleation-doping method are experimentally measured at wavelength near 580 nm. The slow decay rate in millisecond time scale is identified as the radiative decay from the T-4(1) metastable excited state of Mn2+ ions embedded in the ZnSe nanocrystals. Also, two fast decay components are measured at this wavelength with much lower intensities, which can be attributed to the emission tails from the host ZnSe nanocrystals and from the surface-trap states or the self-activated luminescence due to Mn ion pairs, respectively. Size dependences of the radiative decay rates for the Mn:ZnSe samples are measured.