Flexible and optically transparent microwave absorber with wide bandwidth based on graphene

Study of expanding the absorption bandwidth of graphene-based optically transparent microwave absorbers (TMAs) evolved so far encounters a major bottleneck between reducing the sheet resistance of graphene film and fabricating a frequency selective surface (FSS) structure on graphene film, which hinders their practical applications. In this paper, a flexible TMA (FTMA) with wide bandwidth is proposed and realized by using a graphene FSS (GFSS) combined with an oxide-metal-oxide film as a metal ground, where the unit cells of the decimeter-scaled GFSS are electrically disconnected. The GFSS is based on the monolayer graphene grown by chemical vapor deposition (CVD) method, of which the sheet resistance is reduced as low as to about 105 Omega/sq by using HNO3 doping. The equivalent circuital model, and the distribution of the induced surface current and electric field, are provided to reveal the working mechanism of this FTMA. Both the calculated and measured results show that the proposed absorber has a wide bandwidth, low profile, high optical transparency, and good flexibility, which will extend the practical applications of graphene in stealth technologies and electromagnetic compatible facilities. (C) 2019 Elsevier Ltd. All rights reserved.