Spectroscopic ellipsometry is a surface-sensitive, non-destructive, non-intrusive optical technique widely used for thin layers and surface characterization. It is based simply on the change in the polarization state of light as it is reflected obliquely from a thin film sample. Depending on the type of material, spectroscopic ellipsometers can measure thickness from a few Å to tens of microns. It is also an excellent technique for multi-layers measurement.