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Updated: Jul 5, 2026
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Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films
Published on: January 26, 2016
Vacuum ellipsometry as a method for probing glass transition in thin polymer films
Mikhail Yu Efremov1, Shauheen S Soofi, Anna V Kiyanova
1Department of Chemical and Biological Engineering and Center for Nanotechnology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. efremov@wisc.edu
The Review of Scientific Instruments
|May 2, 2008
Summary
A new vacuum ellipsometer effectively probes polymer glass transitions in thin films. Residual gas and ionization gauges can impact measurements, requiring careful experimental control for accurate results.
Area of Science:
- Materials Science
- Polymer Physics
- Surface Science
Background:
- Understanding the glass transition in thin polymer films is crucial for advanced material applications.
- Existing ellipsometry techniques face challenges when applied to polymer films under vacuum conditions.
- Accurate characterization of thin film properties requires specialized instrumentation capable of controlled environments.
Purpose of the Study:
- To design and demonstrate a novel vacuum ellipsometer for investigating the glass transition in thin supported polymer films.
- To evaluate the performance of the developed ellipsometer using standard polymer samples.
- To identify and address experimental challenges and artifacts affecting measurements in thin polymer films under vacuum.
Main Methods:
- Utilized a commercial spectroscopic phase-modulated ellipsometer integrated with a custom-made vacuum chamber.
- Employed oil-free pumps for high vacuum (10^-6 to 10^-8 torr) and a variable temperature optical table.
- Acquired data using a computer-based system to analyze poly(methyl methacrylate) and polystyrene films (20-200 nm thick) on silicon substrates.
Main Results:
- The vacuum ellipsometer successfully detected pronounced glass transitions in poly(methyl methacrylate) and polystyrene thin films.
- Residual gas significantly affected experimental curves, causing decreased or negative apparent thermal expansion coefficients due to water uptake/desorption.
- Ionization gauges introduced spurious phenomena, including data drift, surface roughening, and film dewetting.
Conclusions:
- The developed vacuum ellipsometer is a viable tool for studying glass transitions in thin polymer films.
- Experimental conditions, particularly residual gas composition and vacuum system components, critically influence measurement accuracy.
- Careful control of the vacuum environment and awareness of potential artifacts are essential for reliable thin film polymer analysis.
