Optical properties of Au-Ag alloys: An ellipsometric study

Optical properties of AgxAu1-x alloys were obtained experimentally using spectroscopic ellipsometry measurements on thin films fabricated by electron beam evaporation. Thin film thicknesses varied between 170 and 330 nm, making size effects negligible. Values of the complex refractive index of the pure metals were in good agreement with literature reports. The optical data set reported in this work can accurately reproduce experimental results. This is very important because there are not reliable and systematic optical constants for the alloys. Moreover, we show that the weighted average of the refractive indices of the pure metals fails to represent those of the alloys, not only in the region near the onset for interband transitions but also in the near-IR region.

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