Pore Volume (porosity) in porous silicon

Abstract

The porosity (void fraction per unit volume) of silicon has been varied from less than 1 % to as high as 97 % using electrochemical etching of solid silicon with supercritical drying or silica aerogel reduction with supercritical drying. Fifteen techniques are identified for quantifying porosity in specific physical forms, and a conversion table is provided between porosity, pore volume (void content per unit weight), and bulk density in air. Finally ten applications are given which exploit medium to high (25-95 %) porosity, or the ability to vary porosity significantly within a given structure.