Tailoring the thermal emission of
a material in the long-wave
infrared
(IR) range of 8–13 μm is crucial for many IR-adaptive
applications, including personal thermal management, IR camouflage,
and radiative cooling. Although various materials and surface structures
have been proposed for these purposes, space-selective and dynamic
control of their emissivity is challenging. In this study, we present
a planar surface cavity structure consisting of a Ge2Sb2Te5 (GST) film on top of a thin metal reflector
to modulate its emissivity by using an ultraviolet laser beam. A laser-induced
phase change in GST allowed for the local control of emissivity. The
average emissivity in the long-wave IR range was tunable from 0.15
to 0.77 simply by changing the laser energy deposited on the GST film.
This enabled the laser printing of high-contrast emissivity patterns,
which were erasable by subsequent thermal annealing. Emissivity-modulated
GST cavities could be fabricated on not only rigid substrates but
also flexible plastic substrates such as polyimide. The GST surface
cavity was highly flexible and remained stable upon repeated bending
to a curvature radius of 0.5 cm. This study provides a promising route
for realizing scalable and flexible thermal emitters with tunable
surface emissivity.