Silicon Nanocrystals in Liquid Media: Optical Properties and Surface Stabilization by Microplasma-Induced Non-Equilibrium Liquid Chemistry

Surface engineering of silicon nanocrystals directly in water or ethanol by atmospheric-pressure dc microplasma is reported. In both liquids, microplasma processing stabilizes the optoelectronic properties of silicon nanocrystals. The microplasma treatment induces non-equilibrium liquid chemistry that passivates the silicon nanocrystals surface with oxygen-/organic-based terminations. In particular, the microplasma treatment in ethanol drastically enhances the silicon nanocrystals photoluminescence intensity and causes a clear red-shift (similar to 80 nm) of the photoluminescence maximum. The photoluminescence properties are stable after several days of storage in either ethanol or water. The surface chemistry induced by the microplasma treatment is analyzed and discussed.