image: a, Schematic diagram of the bilayer metafilm and the transition mechanism of GST between different states. The infrared stealth metafilm is based on the bottom metal Mo layer and the top phase change material GST layer. When the temperature exceeds the crystallization temperature Tc, the GST will gradually change from amorphous state to the crystalline state, and once the temperature exceeds the melting temperature Tm, after rapid annealing, the GST can change back to the amorphous state. b, The infrared radiation characteristics of the sample for the two states of GST. When the GST is in the amorphous state, the low average emissivity of the film in the atmospheric window band enables infrared stealth. Meanwhile, within non-atmospheric window band, it demonstrates a high average emissivity and facilitates radiative heat dissipation; When the state of GST changes to crystalline, the average emissivity of the structure in 8-14 μm exceeds 0.67, and the structure turns to the non-stealth state. (c), Demonstration of the different infrared emissivity of the samples before and after the phase transition. In (c), The temperature of the samples with both amorphous (sample A) and crystalline states (sample B) of GST are measured under the background temperature of 30℃, 50℃, 75℃ and 100℃, respectively. Simultaneously, a silicon substrate (sample C) of comparable size is placed as a reference. It can be intuitively found that compared with the sample in the crystal state, when GST is in the amorphous state, the temperature of the sample is significantly lower than the background temperature. Furthermore, as the background temperature increases, there is a continuous increase in temperature difference between samples in the two states. When the background temperature reaches 100℃, the temperature difference between the two samples is as high as 28℃, which is a very intuitive demonstration of the huge change in the infrared radiation characteristics of the sample after the phase transition.
Credit: by Cong Quan, Song Gu et al.
With the rapid development of nanophotonics, spectrally selective infrared stealth technology has achieved great success through the design of metamaterials. However, as the background environment is not static in practical applications, tunable infrared stealth technology has become the center of many recent researches.
In a new paper published in Light: Advanced Manufacturing, a team of scientists, led by Professor Jianfa Zhang and Professor Zhihong Zhu from College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China, and co-workers have developed a switchable infrared stealth bilayer metafilm by using phase change material Ge2Sb2Te5(GST) and the high temperature resistant metal Mo. Based on the metafilm, they flexibly controlled the infrared radiation characteristics of the target by adjusting the GST in different states. When the GST is in the amorphous state, the low average emissivity of the metafilm in the 3-5 μm and 8-14 μm atmospheric window band enabling effective infrared stealth functionality. Additionally, in the 5-8 μm non-atmospheric window band, the high absorptivity ensures excellent radiative heat dissipation capabilities. When GST transitions into its crystalline state, there is a significant increase in average emissivity within the 8-14 μm band and tunes the metafilm to a non-stealth state. Therefore, by switching the state of GST, the target can be switched between the infrared stealth and non-stealth states.
The metafilm is based on the phase change material GST and metal Mo. For the optical properties of GST change dramatically in different states, the infrared radiation characteristics of the target can be flexibly controlled to adapt to the complex and changeable external environment by adjusting the GST in different states. These scientists summarize the operational principle of their non-volatile switchable infrared stealth metafilm:
“To realize non-volatile switch, Ge2Sb2Te5(GST) is one of the most common materials. It has two different states: the amorphous state and the crystalline state. When it turns from the former to the later, its relative permittivity in the infrared range will be significantly increased. By adjusting the GST in different states, the infrared radiation characteristics of the metafilm can be flexibly controlled.”
“Our design employs the high temperature resistant metal Mo along with GST. The metafilm consists of only two layers and it is easy to fabricate at a large scale on both hard and flexible substrates.” they added.
“The presented work represents an important progress in exploring phase change materials for dynamic thermal radiation control and will promote the research towards practical applications of intelligent infrared stealth technology.” the scientists forecast.
Journal
Light: Advanced Manufacturing
Article Title
A Non-volatile Switchable Infrared Stealth Metafilm with GST