Mechanisms of photoluminescent quenching of oxidized porous silicon applications to chemical sensing

Abstract

Silicon can be caused to photoluminesce in the visible by rapid anisotropic etching of bulk samples to form a porous material. Both electrochemical and chemical etching procedures based on an HF reagent have been developed for this purpose. Porous silicon is found to contain nanoscopic silicon particles which have been identified as the luminescent species. The observed photoluminescence is very sensitive to the surface preparation of the porous silicon. Light oxidation of the porous silicon substrate produces a material which is selectively sensitive to Brönsted bases, sulfur dioxide, and halogens. Selective quenching of oxidized porous silicon is associated with the presence of specific types of dangling bond surface states (P b0 and P b1) at the silicon/silicon oxide interface. Interfaces of this type can be fashioned into environmental sensors. Using this approach a gas phase sulfur dioxide sensor has been demonstrated.