Self-limiting processes passive oxidation

We have shown that, in order to exhibit intense PL, the Si nanocrystals must be perfectly passivated. A simple way to achieve this is through natural aerial oxidation. We have followed this process by measuring the photoluminescence as a function of time. Stable conditions are achieved after approximately 6 months. This indicates that the oxidation of Si nanoparticles is a self-limiting process. 

Passive oxidation occurs when the oxide layer that forms on the surface provides a protective coating that inhibits further oxide growth. Passive oxidation is therefore a self-limiting process that gradually slows down (or eventually completely stops) as the oxide grows thicker. 

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