Determination of pore size distribution in thin organized mesoporous silica films by spectroscopic ellipsometry in the visible and infrared range

Spectroscopic ellipsometry is a non-destructive technique, well adapted to the determination of pore volume fraction, pore size distribution and accessible surface area of porous thin films; it is particularly attractive for low-k films. These quantities are deduced from the variation of the refractive index during adsorption and desorption of gas. Several difficulties are encountered for the interpretation of the ellipsometric spectra, in particular the density and refractive index of the skeleton, the determination of the micropores fraction and the variation of the film thickness during adsorption/desorption process should be taken into account. We present results obtained on organized mesoporous oxide films prepared by surfactant templating methods. A combination of spectroscopic ellipsometry measurements in the visible and the infrared ranges is shown to solve part of the uncertainties mentioned above, in particular for silica films, where a realistic estimation of the skeleton refractive index can be obtained. (C) 2003 Elsevier B.V. All rights reserved.