We optimize planar, passive thermal-regulation devices that use the phase-change properties of VO2. We calculate the tunable total emittance, defined as the difference in normalized radiated power in the insulator and metallic states of VO2 at the phase transition temperature. A single-layer VO2/ZnSe/Au device achieves a tunable total emittance of 0.574 in simulation. An optimized multilayer device using the same materials achieves a value of 0.69 in simulation, which outperforms all planar devices found in the literature. We present an analysis showing that an increase in tunable total emittance reduces the temperature fluctuations experienced by the device within a fluctuating environment.
It has been proposed that metal–semiconductor–metal
(MSM) structures can be used to tune the absorptivity of a metasurface
at infrared wavelengths. Indium arsenide (InAs) is a low-band-gap,
high-electron-mobility semiconductor that may enable rapid index tuning
for dynamic control over the infrared spectrum. However, direct growth
of III–V thin films on top of metals has typically resulted
in small-grain, polycrystalline materials that are not amenable to
high-quality devices. Previously, epitaxial wafers were used for this
purpose. However, the epitaxial constraints required that InAs be
used for both the tuning layer and the bottom “metallic”
layer, limiting the range of accessible designs. In this work, we
show a demonstration of direct growth of single-crystalline InAs on
metal to build tunable absorbers/emitters in the infrared regime.
The growth was carried out at a temperature of 300 °C by the
low temperature templated liquid phase (LT-TLP) method. The size of
InAs single-crystalline mesas is ∼2500 μm2, enabling the desired device sizes. The proposed growth and device
enable scalable and tunable infrared devices for various thermal-photonic
applications.
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