Zr-O-N coatings for decorative purposes: Study of the system stability by exploration of the deposition parameter space

The deposition of decorative coatings is an excellent solution to modify the surface of any material, particularly the aesthetic finishing, without altering the properties of the substrate. Transition metal oxynitride films are interesting for many applications, due the simple and economic way to tune between nitride and oxide bonding. In reactive sputtering, this is done by playing with the flows of N2 and O2, leading to variations of properties (e.g. color) in different directions. In this paper, zirconium is selected as transition metal due to the combination of different characteristics (color, biocompatibility, mechanical properties, corrosion resistance). The literature about Zr-O-N films reveals a confinement of chemical composition. Therefore, the aim of this work is the exploration of the deposition parameter space in order to evaluate the stability of the Zr-O-N system, i.e. verify if the chemical composition of the films still falls in the same range after variation of different deposition parameters. To do that, a series of Zr-O-N films is deposited first at different reactive flows, maintaining the remaining deposition parameters constant. The obtained films can be classified in three different groups, based on their chemical composition, crystalline structure, and film growth. These groups can be successfully explained according to the sputtering characteristics, and correlated with the mechanical properties and color of the films measured by nanoindentation and spectrophotometry respectively. The films deposited by variation of other parameters are introduced afterwards and their characteristics are compared with the reference series. •The Zr-O-N system shows a very stable range of chemical compositions.•Different deposition parameters have been varied to test such stability.•Three regions of films are identified: Zr-ZrN, ZrN- Zr2ON2, disordered Zr-O-N.•The color and mechanical properties of the films follow the phase composition.•A different strategy is needed to avoid the verified chemical stability of the Zr-O-N system.