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Ellipsometric Imaging of Drying Sol-Gel Films

Published online by Cambridge University Press:  25 February 2011

Alan J. Hurd
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
C. Jeffrey Brinker
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
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Abstract

Although controlled dip-coating is an established way to apply high quality uniform coatings, the details of the coating and drying process have not been deeply studied. Depending on the physical and chemical state of the sol and the parameters of dipping (dipping angle and speed), a variety of thicknesses and porosities can be achieved [1]. For optical coatings, the refractive index and optical thickness can thereby be controlled.

We have developed a method to view the drying front of a dip-coated film using broad beam ellipsometry [2], or “ellipsometric imaging.” In dip-coated films we take full advantage of the fact that a steady state is quickly reached where the drying line velocity matches the withdrawal velocity; however, the technique might also be used in unsteady situations such as spin coating. Imaging ellipsometry makes it possible to measure the refractive index and thickness profiles of both wet and dry films point-by-point in an entire image at once. These profiles provide important clues as to the relative importance of gravity, evaporation and other phenomena.

Type
Research Article
Copyright
Copyright © Materials Research Society 1988

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