Ellipsometric porosimetry

Ellipsometric porosimetry (EP) is a characterization technique used to investigate the open porosity (in terms of pore size distribution and pore relative content) in (ultra-) thin films. The isothermal adsorption/desorption of probe molecules (which differ in kinetic diameter) in/from the open porosity present in the layer is followed in situ as function of the ratio molecule partial pressure/saturated vapour pressure. Spectroscopic ellipsometry is adopted to monitor the changes in refractive index of the layer upon probe molecule uptake, followed by multi-layer adsorption. At PMP we presently adopt this technique for the characterization of moisture permeation barrier layers with a focus on the transition from micro-(< 2 nm in pore diameter) to meso-porosity (> 2 nm in pore diameter).