ellipsomeetriat

Ellipsometry is an optical technique used to study the optical properties of thin films and surfaces. It measures the change in polarization of light upon reflection or transmission from a sample. This change in polarization, specifically the ratio of the reflection coefficients for parallel and perpendicular polarization components, is characterized by two parameters, psi (Ψ) and delta (Δ). These parameters are highly sensitive to the thickness and refractive index of thin films, as well as their surface roughness.

The technique involves illuminating a sample with polarized light at a specific angle of incidence and measuring the polarization state of the reflected or transmitted light. By analyzing the changes in Ψ and Δ, one can deduce information about the sample's optical constants and thickness. The most common form is spectroscopic ellipsometry, which measures these parameters over a range of wavelengths, providing even more detailed information about the material's optical response across different energies.

Ellipsometry is a non-destructive technique and can be applied to a wide variety of materials, including semiconductors, dielectrics, metals, and organic films. It is widely used in research and industry for applications such as characterization of thin film deposition processes, monitoring etching and cleaning steps, quality control of optical coatings, and studying surface phenomena. Its sensitivity to sub-monolayer changes makes it invaluable for nanoscale material analysis.