Ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals using the variable stripe length technique

The ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals is investigated using the variable stripe length geometry with 200 femtosecond pump pulses. We find that the luminescence lifetimes are in the nanosecond range throughout the entire spectral range. However, no evidence for optical gain is observed even when the pump fluence is in excess of $40mJ∕cm2$⁠. A comparison with similarly prepared, oxide-passivated silicon nanocrystals suggests that oxide passivation plays an important role in providing optical gain from silicon nanocrystals.