Polarizonic-interference colouration of stainless steel surfaces by Au-Al2O3 nanocomposite thin film coating

Abstract

Structural colouration of the stainless steel surface was studied by Au-Al2O3 nanocomposite thin film coating. A wide range of colours was achieved by amorphous, i.e. disordered Au-Al2O3 nano composite thin films where four different structural colours, i.e. magenta, blue, yellow-green and orange, were prepared by varying film thickness and composition. In this case, colours were easily tunable by adjusting the thickness of the film. The colouration mechanism of the amorphous films can be explained by polarizonic interference phenomenon. As the samples were annealed, the Au nanocomposite thin films were crystallized and the range of colours became limited to two colours only: dark yellow-green and light orange. During the annealing process, nanoparticles became enlarged and plasmonic effect caused the limitation of the colour range. Bruggeman theory was applied to predict the colours if the annealed samples.