Absorption-oriented EMI shielding N-doped TiO₂ functional films with enhanced mechanical properties

To develop multifunctional films with excellent electromagnetic interference shielding and mechanical properties, this study proposes an innovative approach to prepare N-doped TiO₂ (TiON) films by magnetron sputtering process combined with thermal oxidation containing low concentration of N. By precisely tuning the N-O flux ratio, we established an oxidation reaction environment containing low concentration of N₂ and realized N-doping in the TiO₂ lattice. The N-doping effectively alters the electronic structure and energy band properties while synergistically modulating the dielectric loss modulation and the formation of nanopillar-fiber morphology. This results in dramatically improved electromagnetic wave absorption efficiency. After 9 h of thermal oxidation at 500 °C, the film is completely transformed into R-TiO₂ with a unique high aspect ratio nanopillar structure, which dramatically enhances the EM wave absorption efficiency through the synergistic effect of dielectric loss modulation and special nanopillar-like morphology. At the nanometer level thickness, it achieves nearly 40 dB of absorption-dominated electromagnetic interference EMI SE, demonstrating comprehensive performance superior to most TiO₂-based films. Concurrently, the N incorporation induces lattice distortion, strengthening dislocation motion resistance and optimizing interfacial bonding and stress distribution. This yields outstanding mechanical properties, including a hardness of 19.3 GPa, an elastic modulus of 195.1 GPa, and maximized H/E_r and H³ /E_r² ratios. Notably, the developed TiON films demonstrate superior comprehensive performance compared to conventional TiO₂-based shielding materials, achieving an optimal balance between exceptional EMI SE and outstanding mechanical durability, which is particularly advantageous for applications in harsh service environments requiring both functional and structural reliability.