Spectroscopic Ellipsometer (SE)

Spectroscopic Ellipsometer M-2000 used for ex-situ measurements at variable angle of incidence (shown here) as well as for in-situ experiments (where the angle of incidence is fixed)

Figure 1

Ellipsometry measures the change of state of polarization of the probing light upon reflection at oblique incidence. If the incident light is linearly polarized, the reflected light will, in general, have an elliptic polarization state. The advantages of spectroscopic ellipsometry over, e.g., reflectivity measurements are that (1) the ellipsometer measures relative quantities, namely ρ = rp/rs, and thus becomes independent of reference signals and (2) it is capable, of measuring (at least) two parameters simultaneously, which makes further analysis to obtain complex quantities such as (effective) dielectric functions or refractive indices obsolete.

The available ellipsometer is a variable angle of incidence (VA), multichannel, rotating compensator spectroscopic ellipsometer (M-2000) supplied by J.A. Woollam (LOT-Europe). The hardware allows for automated measurements for angles of incidence in the range from 40° to 90° and photon energies between 1.1 and 5.0 eV. The simultaneous multichannel detection permits real-time spectroscopic monitoring of kinetic processes at surfaces. Besides of the measurement tasks, the software comes with an important number of modelling tools for the analysis of the resulting spectra, in order to extract theh optical and structural properties of the sample (such as the thickness or composition of the individual layers in a multilayer film). Furthermore, the instrument can also be used to measure transmission and reflectivity spectra.