Determination of pore size distribution and surface area of thin porous silicon layers by spectroscopic ellipsometry

A non-destructive method for investigation of pore size distribution and surface area of porous silicon is presented. Adsorption and desorption isotherms of water in thin ®lms of porous silicon are analyzed using variable angle of incidence spectroscopic ellipsometry. The analysis is based on multilayer optical models and the Bruggeman effective medium approximation. Pore size distribution and surface area are extracted from the isotherms employing the Wheeler theory combined with the Kelvin and Cohan equations. Good agreement is obtained between the calculated pore size distribution and estimations made by scanning electron microscopy. The evaluated speci®c surface area for the porous layers presented here is 180 m2/cm3, which is in good agreement with the value reported in the literature. # 2001 Elsevier Science B.V. All rights reserved.