Optical properties of diffusion-formed Au2Al

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Abstract
Ellipsometric measurements have been made on the intermetallic compound Au2Al to determine the optical constants for photon energies between 0.6 and 3.7 eV. Polycrystalline samples were prepared by the interdiffusion between evaporated thin fils of Au and Al. The optical properties are characteristic of a metallic conductor with an interbrand threshold of about 0.8 eV. The results are compared with optical data for Au, Al and AuAl2, and with x‐ray photoeletron and soft x‐ray emission spectra for Au2Al. As compared with pure gold, it is concluded that interband adsorption is greatly enhance relative to the free‐carrier absorption and that d‐band electrons do not contribute significantly to the absorption observed below 3.7 eV.