Optical properties of laser induced oxynitride films on titanium

This paper presents a study of the optical properties and chemical composition of laser-induced color oxynitride films formed on titanium substrates in a normal-pressure atmospheric environment. The samples were investigated by spectroscopic ellipsometry and X-ray photoelectron spectroscopy. The influence of the laser fluence F on the optical properties of oxynitride films has been found. The thickness of the layers ranges from ∼20 nm to ∼40 nm and increases linearly with F. The determined complex dielectric functions demonstrate two absorption bands, one of them appears in the visible-light wavelength range. We show that the color created by oxynitride films formed on the titanium surface depends not only on the interference effect as commonly assumed, but is also a function of the changes of the optical properties of these coatings.