Infrared Emission Properties of VO2 Films Fabricated with Different Oxygen Flow Ratios

Infrared (IR) camouflage materials are widely used to realize thermal camouflage by adjusting the IR emissivity (ε) of the target object. However, ε modulation without an external energy supply is still a great challenge. Self-regulating VO2 films with different IR emission properties are investigated by adjusting the oxygen flow ratio (O2%) and film thickness. The ε of VO2 films changes before and after the phase transition, and the Δε (the difference of ε before and after the phase transition) of films is different under different O2%, and the maximum Δε can reach 0.49. In addition, the difference temperature (ΔTIR) between the actual temperature (TA: the surface temperature of a standard silicon wafer measured by IR camera, which represents the actual temperature of VO2 samples.) and the IR trapping temperature (TIR: the temperature of VO2 samples measured by IR camera.) is greater than 35 °C after the phase transition. With the range of 1.6 %–2.2 % O2, the IR emission transition temperature (Tε-MIT) and hysteretic width (ΔTε-MIT) increase with increasing O2%. The thickness of the VO2 film affects the IR emission characteristics. The VO2 film is suitable for thermal camouflage materials and for IR anticounterfeiting.