Optical properties of gold and dilute gold-zinc alloys

Abstract

Reflectivity measurements of gold and $\ensuremath{\alpha}$ gold-zinc films have been made; the gold-zinc measurements were made using a differential technique. The detail seen for pure gold in the range 1.2-6.0 eV shows structure in ${\ensuremath{\epsilon}}_{2}$ hitherto revealed only by modulation methods. The imaginary part of the dielectric constant shows the usual two main peaks; the lower-energy one (\ensuremath{\sim}3 eV) is primarily due to transitions from $d$ bands to the Fermi level and the upper one corresponds to $d$-band to conduction-band transitions. The shift of the 3-eV peak with zinc concentration agrees well with Friedel's calculation of the Fermi-energy shift for $\ensuremath{\alpha}\ensuremath{-}\mathrm{CuZn}$ alloys. Our results are in general agreement with the calculated band structures of Connolly and Johnson and Christensen and Seraphin; somewhat better agreement is found with the bands obtained by Connolly and Johnson.