Optical Properties of Gold andα-Phase Gold-Aluminum Alloys

Reflectance measurements at nearly normal incidence were used to investigate the optical properties and electronic band structure of gold and dilute alloys of aluminum in gold. Sample films were prepared, maintained, and measured in ultrahigh vacuum with base pressures less than ${10}^{-9\mathrm{}}$ Torr. Measurements were made in the spectral range 1.1 - 11.5 eV. Shifts in the ${\epsilon }_2$ peak at 3.09 eV ($L_3-L_{2^{\prime }}$) are at one-half the rate expected for the rigid-band model. The change in most transitions upon alloying is consistent with previous assignments. There appears to be a downward shift of $X_{4^{\prime }}$ with respect to the $d$ bands.