Emission properties of manganese-doped ZnS nanocrystals.
We have performed steady-state and time-resolved fluorescence studies on undoped and Mn-doped ZnS nanocrystals with approximately 16 A diameter. While there is no band-edge emission, the intensity of the steady-state blue fluorescence from ZnS surface states decreases upon Mn incorporation, which gives rise to an orange emission. These results show that Mn incorporation competes very effectively with the donor-acceptor surface states for the energy transfer from the electron-hole pair excited across the band gap. In both undoped and doped samples, the time-resolved fluorescence studies establish the presence of a distribution of decay lifetimes possibly due to a number of emission centers in the nanocrystals. A faster short-time decay of the blue emission in the Mn-doped samples compared to that in the undoped sample suggests an additional decay channel for the surface states via an energy transfer from these states to the dopant levels.
Sapra
Sameer
S
Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India. sarma@sscu.iisc.ernet.in
Prakash
Ankita
A
Ghangrekar
Ajit
A
Periasamy
N
N
Sarma
D D
DD