Reflectivity of sputter-deposited gold coatings depending on the layer structure

The reflectivity of gold layers is strongly dependent on their structural characteristics. Reflectivity tends to increase with larger average grain sizes, corresponding to a reduced grain boundary area. A decrease in the grain boundary area results in less restricted movement of free electrons, leading to higher reflectivity. Gold layers produced by evaporation demonstrate a larger average grain size and higher reflectivity compared to those produced by sputtering. The reflectivity of the evaporated layers could not be achieved by modifying the gas supply during sputtering. The addition of N₂ to the Ar supply resulted in a reduction in reflectivity for the sputtered layers.