The Optics Laboratory
Group of Hans Hallen, Physics Department, North Carolina State University
When layers are very thin, such as with self-assembled monolayers (SAMs), standard ellipsometry fails to measure both the thickness and index of refraction of the layer, despite its reputation for being an excellent means of doing that for thicker layers. This is very inconvenient, since one would like to be able to know the thickness to insure a monolayer while having the index as an indicator of layer density. Several approaches have been developed to solve this problem, the most successful being multiple media ellipsometry, in which the sample is measured in several different media, and the data analyzed together to constrain both thickness and index. The problem is that the methods developed to date require non-standard measurements with the ellipsometer, such as measurements around the Brewster's angle only, and analysis is difficult. We describe an approach using only standard ellipsometric measurements, and a relatively straightforward analysis scheme that combines the measurement data and returns a consistent index and thickness for the layer, even when thin. Models show its robustness, and data demonstrates real world success.
More to come once the paper comes out...
More info is in the papers.
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