Home > Techniques and equipment > Ellipsometry

Ellipsometry

Ellipsometry is an optical technique of surface characterization used to determine the optical properties of the materials, in particular the thickness of thin films and optical indices.

A beam of light is directed onto the sample, and the reflected light is analyzed using parameterized models. Unlike most optical methods, which study variations in light intensity, ellipsometry is based on measuring variations in the intensity and the polarization state of the light signal reflected by the sample.

The technique is non-destructive and non-invasive, and can be used as a control tool during sample deposition, etching or processing, thanks to real-time in situ monitoring.

Our UVISEL Horiba Jobin Yvon ellipsometer

To know the rates and have access to our ellipsometer, please contact us by email:

National collaboration with the Institut de Chimie de Clermont-Ferrand (ICCF);
International collaboration with the Central European Institute of Technology (CEITEC) in the Czech Republic.

Technical specifications

Spectral range: 250-825 nm;
Light spot size: 5 mm to 500 microns;
Spatial resolution: ~1 mm2^;
Substrate holder adjustable in X, X and Z directions.

Characteristics required for the materials under study:

flat substrates (size >1cm²), homogeneous (micron-scale), slightly rough (< 50 nm) and absorbing over the 1.5-5 eV spectral range;
homogeneous (micron-scale) thin layers in the sample plane, with thickness d in the range: 0.1 nm < d < 1 μm.

In practice, when the conditions are right, layer thicknesses are determined down to 1 nm, and optical indices down to 5 10^-3.

Examples and applications

The study reports on in situ spectroscopic ellipsometry monitoring of the production process of titanium dioxide thin film and the influence of growth conditions on structure, morphology and optical properties.

Optical index values are determined by ellipsometric analysis of thin films deposited at low temperature by plasma-enhanced chemical vapor deposition.

Left: schematic layer stacking used to describe the thin film deposited on the Si substrate.

Right: the refractive index of TiO₂ (without vacuum inclusions) for varying deposition conditions (ion energy and modulation of injected power for plasma activation), as a function of photon energy. CW mode is represented by solid lines, PD mode by dotted lines.

Ti_xSi_1-xO₂ blend materials are interesting choices for developing new optical and electrical applications.

Ellipsometry is used to determine the optical properties of these thin-film materials, synthesized by plasma-enhanced chemical vapor deposition. The results of the calculation are then compared with the experimental results.

Comparison of Tauc band gap calculated and extracted from the analysis of ellipsometric measurements carried out on a-Ti_xSi_1-xO₂ mixed oxides, as a function of the x composition parameter.