ellipsomeetria

Ellipsometry is a non-destructive optical technique used to characterize thin films and surfaces. It measures changes in the polarization state of light upon reflection from or transmission through a sample. These changes are related to the optical properties and thickness of the material. The technique typically employs a light source, a polarizer, a compensator (optional but common), the sample, an analyzer, and a detector. Light is directed onto the sample at an oblique angle, and the reflected or transmitted light is analyzed.

The measured quantities are typically represented by the parameters Psi (Ψ) and Delta (Δ). Psi relates to the amplitude ratio of the two orthogonal components of the light's electric field, while Delta relates to the phase difference between these components. These values are then fitted to an optical model of the sample, which usually consists of layers with known refractive indices and thicknesses. By adjusting the parameters of the model until the calculated Ψ and Δ values match the measured ones, the properties of the film can be determined.

Ellipsometry is versatile and can be used to determine a wide range of material properties, including film thickness, refractive index, extinction coefficient, surface roughness, and composition. It is widely applied in fields such as semiconductor manufacturing, materials science, optics, and chemistry for applications like monitoring film growth, characterizing optical coatings, and analyzing surface modifications. Spectroscopic ellipsometry, which measures Ψ and Δ over a range of wavelengths, provides more comprehensive information and can be used for materials with complex optical responses.