Ellipsometry measures the change of polarization of an incident beam caused by a sample for determining surface layers.
RP /Rs= tan (𝛹) e i𝛥 (1)
In Situ Spectroscopic Ellipsometry measures a sample "in position” as conditions are varied. The sample can be characterized:
Prior to Film Deposition for Accurate Substrate Characterization
ln Real-time for Thickness and Optical Constants Monitoring
Before exposure to Air/Oxidation