Abstract

The optical performance of a semitransparent electrically conducting film such as tin-doped indium oxide (ITO) may be predicted by a theoretical model of free electrons hosted in a nonabsorbing dielectric material. The parameters of the free-electron model are the dielectric constant, mobility, and density of the free electrons. Following the method described by Berreman¹ we observed a sharp dip in the transmittance of p-polarized light at oblique incidence that is associated with the free-electron plasma resonance in a thin ITO film. Using the known thickness of the film and the estimated dielectric constant in the absence of free electrons, we can adjust the mobility and free- electron density to duplicate this dip with a theoretical model. The fitted parameters can then be used to calculate the optical properties of the material over an extended spectral range. For a 0.145-µm thick ITO film with a sheet resistance of 14.2 Ω, the dip in transmittance is centered at 1.25 µm in the near IR. The density and mobility of the free electrons which were determined from the location and shape of the dip compare favorably with the results of a Hall effect measurement.

© 1988 Optical Society of America