**3.2 Structural evolution**

#### *3.2.1 High-entropy nitride coatings*

High-entropy alloys based on multi-principle elements make it possible to design various nitride coatings. The use of nitride forming multi-principle elements can enhance the physical and mechanical properties that are not achievable in the conventional binary- and ternary-nitride coatings [37]. The high-entropy nitride coatings form amorphous and/or solid solution with face-centered cubic (FCC) structure. The severe lattice distortion and solid solution hardening help in developing high strength nitride coatings for various applications that require wear resistance, corrosion resistance, diffusion barrier, electrical resistivity, biocompatibility or light reflectivity [38]. The versatile sputtering deposition can be used to vary the N2 flow, substrate temperature, and substrate bias to obtain nitride coatings with good physical, chemical, and mechanical properties, respectively.
