Heterophase Engineering of Janus Amorphous MoS ₂ /Crystalline Ni ₃ S ₄ @VO _x with Stacked Built‐in Electric Field for Broadband Microwave Absorption

ABSTRACT The integration of heterophase engineering with stacked built‐in electric fields (BIEFs) provides a compelling strategy for broadband microwave absorbers. Herein, a Janus amorphous MoS 2 /crystalline Ni 3 S 4 @VO x absorber is rationally fabricated via an Ostwald ripening one‐pot solvothermal strategy. Through phase reconstruction, amorphous MoS 2 and crystalline Ni 3 S 4 are in situ anchored onto Janus VO x microspheres, generating abundant amorphous/crystalline heterointerfaces that modulate the electronic configuration of VO x and trigger internal charge redistribution. At the V 2 O 3 ‐MoS 2 and V 2 O 3 ‐Ni 3 S 4 interfaces, spontaneous interfacial charge transfer from amorphous MoS 2 and crystalline Ni 3 S 4 toward V 2 O 3 establishes spatially coupled stacked BIEFs, thereby promoting directional carrier migration and intensifying interfacial polarization relaxation. Meanwhile, the introduction of abundant vacancies induces local electronic structure distortion and electron delocalization around V 2 O 3 and Ni 3 S 4 , strengthening dielectric loss and synergistically promoting electromagnetic wave attenuation. Consequently, the optimized absorber delivers a minimum reflection loss (RL min ) of −59.79 dB at a thickness of 3.0 mm and a broad effective bandwidth (EAB max ) extending up to 7.34 GHz at 2.0 mm, together with a radar‐cross‐section (RCS) reduction of 27.3 dB·m 2 . This work establishes a structure‐electronic configuration‐electromagnetic response correlation in heterophase semiconductor systems, providing new insights into BIEFs engineering for next‐generation broadband microwave absorbers.