Ellipsometer Study of Anomalous Absorption in Very Thin Dielectric Films on Evaporated Metals*

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Abstract
To resolve observed absorption anomalies in the visible region in very thin films on evaporated metals a model is proposed which assumes that: (1) absorption can be separated into x, y, and z components and each of the components decreases exponentially with distance from the film-metal interface and that (2) the absorption at a point in the film is given by the sum of products involving the relative electric-field components and the respective absorption coefficients in the coordinate directions. A procedure is presented for calculation of the relative electric field components for a given film, substrate, wavelength, and angle of incidence. The relative tangential electric field has a dominant influence on the absorption, particularly for very thin films. This conclusion is based on the observed correlation between the slopes of the measured absorption and the calculated tangential field. The substrate has an important influence. This is evident in differences in measured absorption and calculated fields comparing Au and Cr substrates.