Tailoring multispectral infrared camouflage via vacuum-annealed Ag+TiN/TiN/Al₂O₃ thin films

The structure and optical behaviour of Ag + TiN/TiN/Al₂O₃ nanolayer coatings deposited onto Si (100) substrates through magnetron sputtering and subsequent vacuum annealing at 300°C have been investigated in this study. The nanolayer coatings include a co-sputtered Ag + TiN layer, a TiN layer, and an Al₂O₃ barrier layer to ensure thermal stability and prevent oxidation. It has been shown that the crystallization process in Ag and TiN phases is greatly facilitated upon annealing, with no oxides found during X-ray diffraction measurements. FESEM images confirm the improvement in the microstructure and grain refinement. According to UV–Vis spectrometry, annealing results in higher reflectance in the range of ∼16–21% for the as-deposited coatings, reaching ∼36–44% upon annealing. A noticeable change in colour was observed due to increased reflectance. A significant decrease in emissivity has also been achieved upon annealing in MWIR (3–5 µm) and LWIR (8–14 µm) spectral bands, with emissivity in the MWIR band reducing to 0.18 from 0.15. The findings may be explained by defect reduction and improved optical coherence following annealing.