A comparison between light reflectometry and ellipsometry in the Rayleigh regime

The adsorption of Rayleigh particles is analyzed in terms of particle radiu s and surface coverage with thin island film theory with both scanning angl e light reflectometry and ellipsometry around the Brewster angle. A compari son between both techniques shows that an additional uniformity parameter c an be extracted out of the experimental reflectivity data. This gives infor mation about the distribution of the adsorbed mass normal to the surface. F ixed angle reflectometry is less sensitive to surface properties than fixed angle ellipsometry. This is closely related to the fact that ellipsometry measurements provide an extra measurable physical quantity, the change in e llipticity at the surface, which has a weaker but different dependence on s urface coverage and layer thickness. This enables ellipsometry to distingui sh between a broad range of combinations of surface coverage and particle r adii that give similar reflectivity. Fixed angle reflectometry can therefor e only lead to an interpretation in terms of adsorbed mass. Scanning angle reflectometry measurements, on the contrary, can easily be interpreted in t erms of surface concentration and thickness and make further ellipsometry m easurements unnecessary.