Pore Size Distribution in Porous Silicon Studied by Adsorption Isotherms

Porous silicon was obtained by anodic attack of single crystal silicon substrates in 25% hydrofluoric acid solutions. Specific surface area, total porous volume, and pore size distribution of porous silicon have been determined. The experimental technique used is based on the measurement of the volume of gas adsorbed at low constant temperature by the porous silicon. The adsorption isotherms show the general behavior found for porous materials, but at the same time, they show clear differences following different preparation conditions of porous layers. Quantitative analysis using models extensively used in the catalysis field lead to large values for the porous silicon specific surface area and sharp pore size distribution. Mean pore radii are found to vary in the range 20–100Å when forming current density varies from 10 to 240 mA/cm 2 .