MECHANISMS OF PHOTOLUMINESCENT QUENCHING OF OXIDIZED POROUS SILICON -APPLICATIONS TO CHEMICAL SENSING

Silicon can be caused to photoluminesce in the visible by rapid anisot ropic etching of bulk samples to form a porous material. Both electroc hemical and chemical etching procedures based on an HF reagent have be en developed for this purpose. Porous silicon is found to contain nano scopic silicon particles which have been identified as the luminescent species. The observed photoluminescence is very sensitive ro the surf ace preparation of the porous silicon. Light oxidation of the porous s ilicon substrate produces a material which is selectively sensitive to Bronsted bases, sulfur dioxide, and halogens. Selective quenching of oxidized porous silicon is associated with the presence of specific ty pes of dangling bond surface states (P-b0 and P-b1) at the silicon/sil icon oxide interface. Interfaces of this type can be fashioned into en vironmental sensors. Using this approach a gas phase sulfur dioxide se nsor has been demonstrated. (C) 1998 Elsevier Science S.A.