Why use ellipsometry?
Ellipsometry analyzes the change of polarization of light reflected from a sample and yields information about thin film layers that are often even thinner than the wavelength of the probing light itself.
The change of amplitude and phase of the p and s components of the light after the reflection from the sample are depending on film properties like thickness, refractive index and absorption. Ellipsometry measures the change of the amplitudes and phases of s- and polarized light by rotating polarization components. The measured values are psi and delta. These values need to be put into a computer based model of the sample materials to calculate the thickness, refractive index, absorption and a variety of sample properties, including morphology, crystal quality, chemical composition or electrical conductivity. Ellipsometry is an established technology to measure multilayer film thickness, refractive index and absorption.