Sample depolarization effects from thin films of ZnS on GaAs as measured by spectroscopic ellipsometry

Thin films of ZnS grown on GaAs by laser ablation are examined using spectroscopic two‐channel polarization modulation ellipsometry (2‐C PME). It is found that variations in the film thickness over the illumination spot result in the quasidepolarization of the incident light, which can be measured directly using 2‐C PME. Quantitative fits of the ellipsometry data using a distribution‐of‐thicknesses model agree with independent reflectivity measurements of the thickness gradient, and allow for the accurate determination of the optical functions of the ZnS film.