ABSTRACT
This chapter gives a brief description of ellipsometry and its use for developing humidity sensors. Ellipsometry is a noninvasive optical measurement technique. It is known for its ability to determine thicknesses and dielectric functions of thin layers with very high accuracy, thereby providing access to fundamental physical parameters of the sample. It was shown that the ability to determine average monolayer properties gives great opportunities for studying the processes of absorption on the surface of sensing materials, and thus to judge about the humidity change of the environment. However, it must be recognized that this method is not simple and requires careful measurements and calculations, and therefore is more suitable for the study of the properties of surfaces and thin films, than for practical use as a tool for determining the humidity of the air. Examples of such applications of ellipsometry are discussed in this chapter. For example, it was shown that this method, Atmospheric Ellipsometry Porosimetry (EPA), can be used for the pore characterization of studied films. This is especially important for humidity sensors, because of their parameters are largely controlled by the pore size in the humidity-sensitive materials
