Electron-injection-induced Fe atomic valence transition for efficient terahertz shielding in α-Fe2O3@carbon microtubes

Abstract

Currently, commonly used terahertz (THz) absorbers based on metamaterials exhibit limitations in their narrow-band characteristics. This limitation poses a significant challenge when striving to create thinner electromagnetic interference shielding materials capable of delivering exceptional absorption while minimizing reflection across a wide frequency spectrum. In response to this challenge, here we develop a heterostructured material composed of carbon microtubes (CMTs) and (110) α-Fe₂O₃ nanosheets. This heterostructured material shows remarkable THz absorption capabilities and minimal reflectance, owing to the effective alignment between the Fermi energy level of CMTs and the conduction band position of (110) α-Fe₂O₃ nanosheets at the interface. When subjected to THz wave irradiation, there occurs a resonant transfer of excited electrons from the CMTs to (110) α-Fe₂O₃, resulting in a change in the valence state of Fe atoms from Fe(III) to Fe(III⁻). This process contributes significantly to a shielding effectiveness of maximal 75.9 dB at a thickness of 2.45 mm. Furthermore, when combined with polymethyl methacrylate (PMMA), the (α-Fe₂O₃@CMTs)/PMMA films demonstrate a maximal shielding effectiveness of 51.6 dB at a thickness of 300 μm within the frequency range of 0.2–1.8 THz. This breakthrough holds great promise for applications in the fields of aeronautics, astronautics, and the military.