SE is very sensitive to any surface modification that can happen on top of thin film coatings or substrates.
This surface modification is considered as a layer above the surface of the sample. Spectroscopic ellipsometers are capable to determine very accurately its thickness and uniformity over the sample.
Surface measurement applications include:
- Native oxide
- Surface roughness
- Surface treatment
- Surface contamination
It is worth noting that spectroscopic ellipsometry analysis require flat sample surface. Strong roughness causes depolarization of the light, used by ellipsometers to interact with the sample. The maximum measurable roughness is about 50 nm.