Ultrathin Terahertz-Wave Absorber Based on Inorganic Materials for 6G Wireless Communications.

Terahertz waves are gathering attention as carrier waves for next-generation wireless communications such as sixth-generation wireless communication networks and autonomous driving systems. Electromagnetic-wave absorbers for the terahertz-wave region are necessary to ensure information security and avoid interference issues. Herein we report a high-performance terahertz-wave absorber composed of a composite of metallic λ-TiO and insulating TiO nanocrystals (λ-TiO@TiO). This material exhibits a strong terahertz-wave absorption with high values for the real (permittivity, ε') and imaginary parts (dielectric loss, ε″) of the complex dielectric constant. Furthermore, the tan(δ) (≡ ε″/ε') values are significantly high, ranging from 0.50 to 0.76 in the frequency range between 0.1 and 1 THz. An ultrathin film with a thickness of 48 μm recorded a reflection loss of -28 dB (99.8% of the terahertz wave is absorbed by the film). A terahertz-wave absorber with such a small thickness has yet to be developed. Not only does the present material exhibit resistance to heat, light, water, and organic solvents, but it can also be economically fabricated to support various applications, including outdoor uses.