Free-Electron Analysis of Optical Properties of Thermally Evaporated Gold Films

Gold films of thicknesses 150-300 Å were deposited on quartz substrata using vacuum evaporation technique. Spectrophotometric measurements of transmission T and reflection R at normal incidence were performed in the range 0.4-3.0 µm. The real and imaginary parts of the complex refractive index ñ were determined using a developer algorithm bashed on Murmann's exact equations. The accuracy in the determined n and k was found to be ±6.0% and ±1.6%, respectively. The dispersion curve of n slowed an anomalous dispersion in the visible region characterized by a peak at λ = 0.840 µm. The dielectric constants were calculated and presented. The Drude model parameters ω$\text{}_{p}$ and ω$\text{}_{τ}$ and d.c. conductivity were determined and compared. The results showed that such parameters could be obtained from free-electron analysis for the near IR experimental results and the intraband transition contributes significantly to the dielectric functions.