A Graphite-Based Metamaterial Microwave Absorber

The absorption of conventional metamaterial absorbers (MMAs), originating from the electric or magnetic resonance induced ohmic loss, usually has a narrow bandwidth because of the limited surface resistance of the structured metal layers. In this letter, we experimentally demonstrate a broadband MMA by using graphite instead of copper to construct the surface pattern structure. Compared with metals, the graphite has a low electric conductivity, and its skin depth is far more than those of metals. As a result, the effective thickness of our graphite-based absorber, which determines the thickness-dependent resonance, is very sensitive to the thickness of the structured graphite layer. Due to the relatively large surface resistance and the sensitive tunable thickness-dependent resonance, our design achieves an absorption bandwidth (less than -10 dB) from 12.7 to 18 GHz. Our results may provide an effective way to tune the thickness-dependent resonance and to broaden the absorption bandwidth of MMA.