Optical constants of aggregated gold films

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Abstract
The optical properties of aggregated gold films have been studied in the visible and near infrared. From the measurements of the normal transmittance and reflectances at two different angles, the effective optical constants and the effective optical thickness could be derived. The films were produced by evaporation on a hot substrate to form a highly aggregated structure; the particles that form the films were relatively large; i.e., the thickest films had particles attaining modal sizes up to 1500 Å. By considering these particles as rotational ellipsoids and by assuming a plausible distribution function of the depolarization factor, we were able to describe the optical properties of the aggregated films and to obtain satisfactory agreement with experiments. The proposed analysis permitted determination of several parameters that characterize the films, in particular the filling factor and the mean effective depolarization factor.