Abstract

The optically induced free-carrier absorption coefficient of densely packed 2×10^18 cm−3 Si nanocrystals (NCs) embedded in a glass matrix was accurately measured in the near-infrared using two complementary pump-probe techniques. When compared to established carrier dynamical models, the dependence of the absorption coefficient on optical pump intensity reveals enhanced nonradiative recombination at high pump intensity >10 KW/cm2, which can be explained by the interaction of excited carriers located in spatially separated NCs. The rate of recombination due to the interaction between a pair of excited NCs is determined to increase inversely with the sixth power of their separation distance and is indicative of near-field dipole dipole energy transfer. These results explain the source of an apparent inconsistency in power-law behavior found in previous carrier dynamics studies on similar materials which did not account for this interaction.