Abstract
Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection. Resistive and/or magnetic composite materials are used to reduce the backscattered microwave signals. Inability to control electrical properties of these materials, however, hinders the realization of active camouflage systems. Here, using large-area graphene electrodes, we demonstrate active surfaces that enable electrical control of reflection, transmission and absorption of microwaves. Instead of tuning bulk material property, our strategy relies on electrostatic tuning of the charge density on an atomically thin electrode, which operates as a tunable metal in microwave frequencies. Notably, we report large-area adaptive radar-absorbing surfaces with tunable reflection suppression ratio up to 50 dB with operation voltages <5 V. Using the developed surfaces, we demonstrate various device architectures including pixelated and curved surfaces. Our results provide a significant step in realization of active camouflage systems in microwave frequencies.
Highlights
Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection
The working principle of the device is based on the electrostatic tuning of high mobility carriers on graphene electrodes without using metallic structures
This simple device architecture yields an unprecedented ability to control charge density on large-area graphene electrode, which operates as a tunable metal
Summary
Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection. Heating or illuminating a bare semiconductor surface with a light source can generate free carriers; but, these techniques are not practical for realistic device configurations Tunable materials such as ferroelectric materials[29,30] and composite polymers[31,32] have been studied for possible active microwave surfaces. Inability to fabricate these materials over large area and weak modulation of dielectric properties prevents realization of adaptive microwave surfaces. Another approach is to use distributed active circuit elements (diodes, transistors or photoswitches) integrated with passive metallic structures[33,34]. Monoatomic thickness, tunable high mobility charged carriers together with the large-area synthesis of graphene provide unique configuration for the realization of the adaptive microwave surfaces
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