What is ellipsometry?

Ellipsometry is an optical technique used to investigate the dielectric properties (complex refractive index or dielectric function) of thin films. It measures the change in polarization of light upon reflection or transmission and compares it to a model. It's commonly used to determine the thickness, refractive index, and other optical constants of thin films and multi-layer stacks in various fields like semiconductor manufacturing, materials science, and surface chemistry.