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Content archived on 2024-05-29

Development of new hard decorative coatings based on transition metal oxynitrides

Final Report Summary - HARDECOAT (Development of new hard decorative coatings based on transition metal oxynitrides)

The ultimate aim of the HARDECOAT project was to develop new functional coatings for decorative, protective, as well as for micro-optoelectronics applications. The Transition metal oxynitrides (TM-O-N) based coatings were deposited by Physical vapour deposition (PVD) techniques, especially the reactive sputtering method was used. The concept was to combine the excellent mechanical properties of nitrides with the specific optical characteristics of the oxides. By altering the deposition conditions, coatings with composition varying from oxides to nitrides were reached, thus allowing the exploration of the unknown and vast spectrum of oxynitride thin film compounds.

Since conventional reactive sputtering with a simultaneous injection of two gases (oxygen and nitrogen) was not a suitable process to deposit metal oxynitride coatings, an original deposition technique was developed for the deposition of TM-O-N coatings with adjustable and flexible chemical compositions, which was based on the already acquired pre-existing know-how of Reactive gas pulsing process (RGPP).

Considering the reactivity towards the oxygen and nitrogen, six different materials were selected amongst the transition metal series in order to better understand the material properties and thereby, helping the transition of laboratory-scale towards the industrial environment. Four reactive sputtering processes were developed in order to deposit transition oxynitride thin films, namely the conventional reactive sputtering, pulsed power, gas mixture, as well as reactive gas pulsing process. Each process was optimised with the aim of tuning the metalloid concentrations and therefore, the behaviour of as-deposited coatings.

The results clearly revealed that the transition metal oxynitride thin films exhibited atypical performances, namely metallic and semiconducting behaviours. The synthesis of transition metal oxynitride compounds turned out to be an original way to produce multifunctional thin films. The oxynitride coatings proved to be competitive with regards to their specific intrinsic colour, their optical and electronic properties, as well as their wear and corrosion resistance. As a result, the applications would target the decorative, opto-electronic and the micro-technology sectors.