Optical and microstructural properties of decorative Al/Ti/TiO2 interference coatings

This paper presents a study of the optical properties and the microstructure of interference Al/Ti/TiO2 systems obtained by gas injection magnetron sputtering (GIMS). The samples are examined by means of spectroscopic ellipsometry, atomic force microscopy and spectrophotometry combined with colorimetric measurements. The optical constants of the Al, Ti and TiO2 layers are determined and carefully studied. The thickness of dielectric films varies from 23 nm to 49 nm and directly determines the color of a sample from orange to blue, respectively. The thickness of Ti films ranges from 0 nm to 125 nm which corresponds to both the semitransparent and opaque titanium layers. The colors of the Al/TiO2 interference systems are not highly saturated because of the high reflectance of aluminum in the visible spectral range. The introduction of a Ti film between Al and TiO2 reduced the effective amount of reflected light. Moreover, the thickness of the titanium layer is associated with the color saturation of the Al/Ti/TiO2 multilayered systems.