Light emission from silicon nanocrystals - Size does matter!

A brief overview of two recent Si nanocrystal studies undertaken at the Australian National University is presented: recent work on hydrogen passivation of non-radiative defects and attempts to measure optical gain in waveguide structures. In the first study, a generalized treatment of hydrogen passivation and desorption is employed to model the influence of hydrogen on silicon nanocrystal luminescence. Values for reaction-rate parameters are determined from the model and found to be in excellent agreement with values previously determined for paramagnetic Si dangling-bond defects (P-b-type centers) found at planar Si/SiO2 interfaces. In the second study, an attempt is made to measure optical gain in silicon nanocrystals by monitoring the intensity of a probe beam propagating in a waveguide structure containing silicon nanocrystals during photo-excitation of the nanocrystals. The probe beam is shown to be attenuated by the excitation demonstrating the dominance of absorptive processes. No gain was observed.