Ellipsometry
Using the spectral ellipsometer SE850 (SENTECH Instruments GmbH) the Innovent institute has a powerful tool for the optical characterisation of transparent thin films in the UV-Vis and NIR region. Applying this device refractive indices in a spectral range of 350 to 820 nm and thicknesses of thin films and film systems can be measured. In combination with the FTIR spectrometer the measurement range can be broaden up to 2300 nm. The size of the light spot can be decreased to about 200 µm using the microspot option of the device.
The SE850 works on the base of the Step-Scan-analysator principle and guaranties together with the diode array detector highest sensitivity.
The software SPECTRARAY II allows a substantial analysis of thin films:
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thickness of single layers and layer stacks
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determination of optical constants
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determination of surface roughness and interfaces (effective medium approximation)
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gradient layers
Example
The figure shows the measured delta and psi values vs. wavelength together with the results of a fit procedure. The fit was done assuming a defined layer stack. The measured TiO2-SiO2-Si-layer system could be fitted with the parameters shown in the table.
