Tailoring\nMechanical\nand Optical Properties of Sputtered\nSiN<sub><i>x</i></sub>/BN Coatings

The swift evolution of contemporary\nelectronics products,\nsuch\nas flexible screens and wearable electronic devices, highlights the\nsignificance of flexible protective coatings, which combine superior\nmechanical and optical properties. Even though the recently developed\npolymer protective coatings can satisfy requirements for flexibility\nand transparency, their intrinsic nature often results in a hardness\nbelow 1 GPa, rendering them susceptible to scratches. On the other\nhand, traditional inorganic coatings, known for their high hardness\nand transparency, fall short of meeting flexibility requirements.\nIn the present study, a SiN<sub><i>x</i></sub>/BN periodical\nnanolayered coatings (PNCs) structure has been tailored to achieve\nhigh mechanical durability, transparency, and flexibility. In SiN<sub><i>x</i></sub>/BN PNCs, the optical and mechanical properties\nof the single-layer SiN<sub><i>x</i></sub> film are crucial\nto the overall performance of the PNCs. Therefore, pulse direct current\n(DC) magnetron sputtering was optimized first to enhance the ionization\nefficiency of Si and N, thereby promoting their reaction and diminishing\nthe presence of elemental silicon in SiN<sub><i>x</i></sub>. The effects of the pulse frequency and duty cycle on SiN<sub><i>x</i></sub> were evaluated. Additionally, the influence of the\nthickness ratio and modulation periods on the overall performance\nof the SiN<sub><i>x</i></sub>/BN PNCs was investigated.\nAs a result, a SiN<sub><i>x</i></sub>/BN coating with sapphire-grade\nhardness, almost no optical absorption in the visible–near-infrared\n(vis–NIR) range, high wear resistance, and exceptional flexibility\nwas demonstrated.