The Effect of Surfactants on the Reactivity and Photophysics of Luminescent Nanocrystalline Porous Silicon

• Published in: Advanced functional materials 2002-08, Vol.12 (8), p.495-500
• Main Authors: Canaria, C.A., Huang, M., Cho, Y., Heinrich, J.L., Lee, L.I., Shane, M.J., Smith, R.C., Sailor, M.J., Miskelly, G.M.
• Format: Article
• Language: English
• Subjects: Photoluminescence; Silicon porous; Surfactants
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/1616-3028(20020805)12:8<495::AID-ADFM495>3.0.CO;2-8

The effect of aqueous cationic and anionic surfactant solutions on the chemical stability and photoluminescence (PL) of n‐ and p‐type porous Si has been studied. Exposure of either n‐ or p‐type porous Si to aqueous solutions of the surfactants dodecyltrimethyl ammonium bromide (DTAB) or sodium dodecylsulfonate (SDSulfonate) at ≤ pH 3.0 results in quenching of the visible PL from this material via two distinct mechanisms. In the case of the cationic surfactant DTAB, irreversible quenching of the PL is accompanied by chemical corrosion of the porous Si sample, as determined by infrared spectroscopy. The enhanced corrosion rate is attributed to an increase in the reactivity of the hydrides present on the Si surface towards water, induced by adsorption of the cationic surfactant. Hydrogen evolution in this reaction was confirmed by gas chromatography. In contrast, the anionic surfactant SDSulfonate physisorbs to either n‐ or p‐type porous Si samples, and quenches PL without resulting in a significant amount of oxidation. The mechanism of quenching for the anionic surfactant is attributed to local dielectric effects that increase the non‐radiative decay rate in porous Si. Dramatic differences are observed in the chemistry and photophysics of nanocrystalline porous Si exposed to surfactants with cationic or anionic headgroups. The cationic surfactant dodecyltrimethylammonium bromide causes irreversible quenching by catalyzing rapid corrosion of the silicon surface, visualized by IR spectroscopy. The anionic surfactant sodium dodecyl sulfonate, on the other hand, physisorbs to the surface and leads to reversible photoluminescence quenching, probably due to local dielectric effects that increase the non‐radiative decay rate in porous silicon.