Polarization behavior during porous silicon formation: effect of surfactant

The effect of surfactant on the polarization behavior during porous silicon formation has been studied for p- and p(+)-type silicon wafers. The presen ce of surfactant showed strong effects on p-type silicon, whereas the pi-ty pe silicon polarization curve changed negligibly with a surfactant. The ani onic surfactant increased the overpotential; it was decreased by the cation ic surfactant. The space charge layer mainly determines the dissolution pro cess, since p-type silicon, which has a smaller capacity, was more affected than p(+)-type silicon. This is also supported by the capacity measurement s of a p-type silicon: a more positive flatband potential in the anionic su rfactant solution and a less positive flatband potential in the cationic on e. The surface properties of p-type porous silicon have also been investiga ted by infrared spectroscopy. The absorption bands change in shape and in i ntensity, depending upon the surfactant. In particular, the cationic surfac tant reduced the absorbance. The decrease is due to the chemical dissolutio n of the porous silicon layer. We can also see a correlation between the in tegrated absorbance and the electrode potential. (C) 2001 Elsevier Science Ltd. All rights reserved.