Using a fast dual-wavelength imaging ellipsometric system to measure the flow thickness profile of an oil thin film
Abstract
Dual-wavelength light sources with stroboscopic illumination technique were applied in a process of photoelastic modulated ellipsometry to retrieve two-dimensional ellipsometric parameters of thin films on a silicon substrate. Two laser diodes were alternately switched on and modulated by a programmable pulse generator to generate four short pulses at specific temporal phase angles in a modulation cycle, and short pulses were used to freeze the intensity variation of the PEM modulated signal that allows ellipsometric images to be captured by a charge-coupled device. Although the phase retardation of a photoelastic modulator is related to the light wavelength, we employed an equivalent phase retardation technique to avoid any setting from the photoelastic modulator. As a result, the ellipsometric parameters of different wavelengths may be rapidly obtained using this dual-wavelength ellipsometric system every 4 s. Both static and dynamic experiments are demonstrated in this work.
- Publication:
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Applied Surface Science
- Pub Date:
- November 2017
- DOI:
- 10.1016/j.apsusc.2017.01.100
- Bibcode:
- 2017ApSS..421..465K
- Keywords:
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- Imaging ellipsometry;
- Stroboscopic illumination;
- Film thickness profile