Study of the thermal oxidation of sputtered multi-layered TiN/Cu/TiN films

To obtain functional films with both electromagnetic shielding and infrared stealth capabilities, this paper employs a method combining magnetron sputtering technology and thermal oxidation process. A TiN/Cu/TiN multilayer film is designed by magnetron sputtering, and then is oxidized at different temperature (300, 500, 700 °C) respectively. The properties of the films are improved with the increase of the thermal oxidation temperature, especially at 700 °C. After thermal oxidation at 700 °C, the film is completely oxidized to form a CuTiO oxide film with a unique hybrid structure of microfibers and nanoparticles. The uniformly and randomly oriented fibers in CuTiO film form a high-conductivity network which can provide a convenient transmission path for carrier transmission, reducing the film's resistivity. Depend on the high absorption of electromagnetic waves by these fibers, CuTiO oxide film has the best electromagnetic shielding performance. The shielding loss is up to 55 dB, mainly from the absorption loss, and the reflection loss is only 2 dB. Most of these fibers are around a few microns in size, which is close to the infrared wavelength of 3–5 μm and 8–14 μm, resulting in a strong Mie scattering, leading to a high decrease in the absorption of infrared waves. Thus, the infrared emissivity is significantly reduced accordingly. The method in this paper not only obtains the multifunctional film, but also solves the problem of secondary pollution of electromagnetic radiation dominated by reflection loss and the deterioration of infrared emissivity with the increase of operating temperature.