Cu@SnO₂/rGO to Cu@Sn/rGO transition: A strategy for tuning plasmon resonance and Schottky junctions in excellent microwave absorbers

Achieving high attenuation properties and tunable absorption frequencies is crucial for the development of advanced electromagnetic wave absorbers. The structure design of heterogeneous interfaces is an effective way to control electromagnetic parameters and improve absorption capacity. Herein, based on the semiconductor-metal-dielectric structure, the rationally designed Cu@SnO₂/rGO composites with two structure types of Cu/rGO interfaces including metal surface plasmon resonance (SPR) and Cu@SnO₂ Schottky junction, which enables manipulation and accelerated charge transfer. More importantly, the reduction of Schottky barrier by controlling the annealing temperature further directs the formation of charge flow and accelerates charge migration. Due to the synergy of SPR effect, strong interfacial polarization, high attenuation as well as the conductive network formed by the massive interfaces, the dual-strong microwave absorption performance and tunable absorption frequency were exhibited at 700 °C. The minimum RL value is −50.40 dB (10.80 GHz, 3.0 mm) and −50.10 dB (16.72 GHz, 2.0 mm). In addition, the range of tunable frequencies are 9.04–12.64 GHz at 3.0 mm and 14.08–18.00 GHz at 2.0 mm, respectively. This work provides a new strategy to design heterostructural absorbers and illustrates the importance of hetero-interfacial effects on microwave loss and frequency modulation mechanism.