Strategies to control the spectral properties of Au–Ni thin films

• Optical properties of metastable (Au,Ni) calculated using density functional theory
• Properties of nanoscale stacks of Au and Ni calculated using optical film theory
• Alloying of Au and Ni allows for extensive control of optical properties.
• An equivalent color gamut can be achieved by nanoscale stacks of the pure elements.
• Predictions of color gamut verified using samples fabricated by magnetron sputtering

Gold and nickel have quite different dielectric functions. Here we use a combination of calculation and sample manufacture to assess two strategies by which thin films of these elements can be produced with a controlled range of far-field optical properties. In the first approach, control can be achieved by manipulating the density of states of metastable solid solutions, which in turn controls the dielectric function. In the second approach the optical properties of the films are controlled by varying the geometry of stacks fabricated from the constituent elements. We show that the two approaches can produce equivalent results so both are viable options in practice. Modeling is used to reveal how the structure controls the optical properties and to map out the possible color gamut. Predictions are tested with thin film samples fabricated by magnetron sputtering.