Dual relaxation behaviors driven by a homogeneous and stable dual-interface charge layer based on an EGaIn absorber

Interface engineering, by modulating defect distribution and impedance at interfaces and inducing interfacial polarization, has proven to be an effective strategy for optimizing dielectric properties. However, the inherent incompatibility between heterogeneous phases presents a significant challenge in constructing multi-heterointerfaces and understanding how their distribution influences dielectric performance. Herein, we constructed an EGaIn@Ni/NiO/Ga₂O₃ composite structure by employing a low-intensity ultrasound-assisted galvanic replacement reaction followed by high-temperature annealing. The controlled addition of Ni salts allowed for the fine-tuning of Ni, NiO, and In concentrations and their spatial distribution within the interfacial architecture. Annealing treatment induced a transition from amorphous to crystalline phases, triggering dual relaxation behaviors between EGaIn/Ni and NiO/Ga₂O₃. Additionally, significant charge accumulation was observed at the NiO/Ga₂O₃ interface, likely due to the substantial work function difference between Ni and NiO, coupled with the low barrier height between EGaIn and Ni, which facilitates electron migration. Consequently, the optimized samples exhibited a maximum absorption bandwidth of 7.92 GHz, which is the highest among the EGaIn-based absorbers reported in the literature. This work not only elucidates the mechanism by which multi-heterogeneous interfacial distributions regulate the dielectric properties but also provides an effective approach for modulating the electromagnetic wave performance of liquid metals.