Spectroscopic ellipsometry analyses of thin films in different environments: An innovative “reverse side” approach allowing multi angle measurements

An innovative ellipsometer sample holder has been designed and tested in order to measure thin films optical properties under different environments and so infer the porosity through effective medium approximation models. Compared to commercial cells that require a fixed angle of incidence or a cell with a cylindrical geometry, we present a simple cell in which the sample is mounted in “reverse side”, allowing multiple angle analyses without the need for cell windows. Standard ellipsometry measurements are compared to the “reverse side” approach in order to confirm the feasibility of this new procedure, obtaining the same refractive index dispersion curves in both cases. Then different samples have been tested in “reverse side” under different environments to measure porosity. The multiangle approach has been found useful to improve the fitting of the experimental data by reducing both the fitting error and the correlation between parameters.