Colloidal suspensions of silicon nanocrystals: from single nanocrystals to photonic structures

Colloidal suspesions of Si nanocrystals (NCs) are prepared from light-emitting porous Si grains obtained by mechanical pulverization of electrochemically etched layers. Sedimented and/or filtered Si NCs sols reveal a green photoluminescence (PL) band around 530 nm, which is interpreted as radiative recombination of electron-hole pairs inside Si NCs with diameter about 2 nm. These colloidal solutions have multiple advantages for both fundamental investigations and for nanotechnology. In one extreme, single molecule spectroscopy techniques can be applied to investigate PL of single grains of Si NCs dispersed on substrates from highly diluted solutions. On the other hand, concentrated suspensions enable us to fabricate bulk samples with embedded Si NCs or to prepare self-organised nanostructures on surfaces.