SYNTHESIS AND PROPERTIES OF LIGHT-EMITTING SILICON NANOCRYSTALS, C.
Service des Photons, Atomes et Molécules, Laboratoire Francis Perrin
(CEA-CNRS URA2453), DSM, CEA-Saclay, 91191 Gif/Yvette Cedex, France.
Silicon is an indirect gap semiconductor and thus a very poor light
emitter in the bulk. The discovery of the intense photoluminescence
(PL) in nanocrystalline Si (nc-Si) has opened a tremendous research
activity, regarding the large potentialities of this element in
optoelectronic. Moreover, being biologically compatible, nc-Si is also
very attractive as medical tracer. I will present results showing that
quantum-size effects can explain all the PL characteristics of nc-Si,
and that passivation of the nanocrystal surface is of particular
importance, since it appears to control the PL quantum yield.
One of the challenge is to synthesise weightable quantities of nc-Si
with controlled size and structure. I will present recent results
obtained in this direction, using CO laser pyrolysis of silane in a
gas flow reactor. In this method, molecules are dissociated, and
subsequent nucleation of Si nanoparticles occurs in a flame. Their
size and structure are sensitive to the gaseous flow and laser power.
By adjusting these parameters, quantities of Si nanoparticles have
been synthesised with size in the [10-20] nm range, and even less.
Transmission Electron Microscopy observations and first PL
measurements will be discussed, focusing on the role of the surface