Structural-color-control by AlN coating on rough-surface Al film

Abstract

The surface roughness of the rf-sputtered Al film has been controlled by using a method of two steps deposition at two different substrate temperatures (473 K and 300 K). One of the Al films with a proper surface roughness shows low specular reflection and high diffuse reflection in visible region, and looks like white colour without gloss. When a transparent (50-400 nm thick) AlN films is deposited on the roughened Al film, its color is changed into wheat, light-skyblue, khaki, and light-plum depending on the AlN film-thickness. It is revealed that the major part of the whole reflection from the specimen is diffuse reflection due to the surface roughness, and the variety of color without gloss is caused by the interference effect by the deposition of AlN film.