Transmittance and reflectance <i>i</i> <i>n</i> <i>s</i> <i>i</i> <i>t</i> <i>u</i> measurements of semicontinuous gold films during deposition

Abstract

We have continuously measured in situ reflectance and transmittance of percolating gold films over the entire range of surface coverage P, in the IR regime (1.7 and 2.2 μm). The samples present similar optical and electrical behavior, when compared on a normalized thickness scale. In the fractal region, close to the percolation threshold, the optical properties show a linear dependence on the surface coverage parameter, in agreement with a renormalization argument previously suggested. A strong absorption (about 40%), whose origin is not well understood, is found in the fractal region. The interpretations previously proposed by other authors are not applicable. We conclude that geometrical effects must dominate the optical properties over a large range of surface coverage.