Possible explanation of the contradictory results on the porous silicon photoluminescence evolution after low temperature treatments

The modification of the porous silicon photoluminescence (PL) after a low level thermal oxidation at 300°C is studied by analyzing the surface chemical composition using infra-red spectroscopy. The amount of oxide is determined quantitatively. Two different porosities of porous silicon are studied: 70% and 80%. In the case of the 70% porosity porous layer, this thermal process leads to an important PL enhancement in the early stages of oxygen incorporation followed by a degradation at higher oxidation levels whereas the photoluminescence of the 80% porosity porous layer only decreases. It is shown how this new analysis can account for the different and often contradictory results on the PL behavior under various low-temperature oxidation processes.