Design of high transparent infrared stealth thin films based on FTO/Ag/FTO structure

Multi-spectral compatible stealth materials become an imperative development trend, especially visible and infrared compatible stealth materials have become a top priority in the field of optoelectronic stealth technology. However, the demands of infrared stealth and visible stealth on spectral response are different, which makes it difficult to reconcile the design of functional coupling materials. Therefore, it is crucial to develop selective control technology of optical characteristics. A visible and infrared compatible stealth superstructure thin film is proposed based on the FTO/Ag/FTO stacked film structure. A collaborative design method for high visible transmission and low infrared radiation is established, and the mechanism of microstructure characteristics affecting visible transmission and infrared reflection spectra is explained. The highly transparent infrared stealth thin film is optimized, and its compatibility stealth performance is tested and characterized through the use of visible transmission spectroscopy, infrared reflection spectroscopy, and thermal imaging characterization techniques. It has shown that visible transmission depends on the coupling and matching effect between the semiconductor dielectric layer and the metal layer, while infrared radiation suppression mainly depends on the metal layer. As the thickness of FTO film increases, the visible transmission peak undergoes a red shift, leading to a flattening of the transmission spectrum curve, the average transmission first increases and then gradually decreases. As the thickness of Ag thin film layer increases, the transmission peak of visible undergoes a blue shift, causing the transmission spectrum curve to tend a high-frequency transmission state, narrowing the frequency domain of visible transmission and gradually decreasing the average transmittance. At the same time, the infrared reflectance increases with the increase of Ag film thickness, but the change amplitude significantly decreases when the Ag film thickness is greater than 18 nm. When the thickness of the optimized FTO/Ag/FTO film structure is 40/12/40 nm, it has a high level of background perspective reproduction and high-temperature infrared radiation suppression ability. The average transmittance of 0.38~0.78 μm visible light band is 82.52%, and the average reflectance of 3~14 μm mid-far infrared band is 81.46%. The radiation temperature of the sample is 49 ℃ and 75.8 ℃ lower in mid infrared and far infrared than that of the quartz sheet at 150 ℃, respectively. The new stealth film can be attached to the camouflage coating surface of special vehicles to achieve visible and infrared compatible stealth, and can be used for cockpit windows to ensure thermal insulation, temperature control, and infrared stealth without affecting the field of view. This study can provide a new approach for the design and application of visible and infrared compatible stealth materials.