Silicon Nanocrystals With Organic Passivation: More Efficient Luminescence From Silicon

Silicon nanocrystals (Si-ncs) attract the scientific community's attention as possible silicon-based light sources for optoelectronics and fluorescent markers. Even the most commonly studied type of Si-ncs, i.e. Si-ncs passivated by native oxide, show 5 orders of magnitude stronger luminescence (having quantum yield of several per cent) in comparison with volume silicon, they still do not draw level with the commercially produced light-emitting semiconductor nanocrystals on the basis of direct band gap semiconductors (CdS, CdSe - quantum yield about 50%). Using original photochemical treatment, however, we manage to substitute the original passivation by native oxide for surface capping with methyl groups. Owing to this passivation change, we obtain Si-ncs in the form of transparent colloidal dispersion with much better luminescent properties which are approaching commercially available nanocrystals on the basis of direct band gap semiconductors such as CdS or CdSe.