Infrared study of the oxidation of porous silicon: evidence of surface modes

Abstract

Porous silicon is characterized by a large specific area and a large chemical reactivity. These characteristics, although attractive for sensing applications, led to an unstable behaviour. Different oxidation methods have been proposed in order to stabilize the luminescence and other properties of PS. FTIR spectroscopy has been one of the main techniques used to study the PS oxidation process. Photoluminescence is usually present in PS having a nanostructure scale. The presence of different levels of structures contributes to the spectrum with different spectral shapes and with different oxidation kinetics. In this work we show that large scale structures contribute with TO modes, evolving quickly up to saturation, and small scale structures contribute mainly with Fröhlich surface modes which evolve slowly.