When the film thickness is considered as a parameter, a system composed of a transparent film on an absorbing substrate (in a transparent ambient) is characterized by a range of principal angle over which the associated principal azimuth varies between 0° and 90° (i.e., ) and the reflection phase difference Δ assumes either one of the two values: +π/2 or −π/2. We determine the principal angle and principal azimuth as functions of film thickness d for the vacuum-SiO2-Si system at several wavelengths as a concrete example. When the film thickness exceeds a certain minimum value, more than one principal angle becomes possible, as can be predicted by a simple graphical construction. We apply the results to principal-angle ellipsometry (PAE) of film-substrate systems; the relationship between and during film growth is particularly interesting.
© 1977 Optical Society of AmericaFull Article | PDF Article
M. S. A. Yousef and A.-R. M. Zaghloul
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