Optical coatings of durability based on transition metal nitrides

Abstract To resist dust, windblown sand, moisture, acid rain and salt fog, infrared-reflective coatings (IRCs), solar-selective absorption coatings (SACs), and transparent heat-regulating coatings (THRCs) should have high durability. However, traditional IRCs, SACs and THRCs are mainly composed of pure metals (e.g., Al, Ag and Au) and thus often have poor durability. Studies have shown that the use of nitrides of groups IVB, VB and VIB transition metals (TMNs, TM = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W) is an effective method to improve the durability of these optical coatings and at the same time can broaden the applicability of TMNs in optics. In recent years, researchers have paid great attention to the development of TMN-based optical coatings. However, there are few studies on the effect of material selection and microstructure control on the optical properties and durability of these coatings. In this review, the recent advances on the study of TMNs used as IRCs, SACs and THRCs are reported in detail, and relationships among material design, structure control and performance improvement of these optical coatings are revealed. Compared with traditional optical coatings, TMN-based optical coatings have higher durability and wider potential applications. In addition, challenges of optical research on TMNs are also discussed.