Photoluminescence spectrum and dynamics in oxidized silicon nanocrystals: A nanoscopic disorder system

We have studied luminescence properties of nanometer-sized Si crystallites fabricated by laser breakdown of SiH₄ gas. An exponential absorption tail is observed and red photoluminescence (PL) appears in the exponential tail. The PL decay behavior is characterized by a stretched exponential function. At higher temperatures, the effective PL decay rate τ^-1 depends exponentially on the monitored phonon energy {}{ω}: τ^-1{∝}exp({}{ω}/E_τ), where E_τ is a constant depending on temperature. On the other hand, at low temperatures, the PL lifetime is almost independent of the PL wavelength and phonon-related structures in the PL spectrum are not clearly observed under resonance excitation. The order and disorder natures of Si nanocrystallites are discussed. {} 1996 The American Physical Society.