A joint research team including Professor Shin-ichi Ohkoshi of the School of Science at the University of Tokyo, and Nippon Denko announced on January 31 that they synthesized a new titanium oxide material, surface-coated lambda trititanium pentoxide, and so developed a new high-performance terahertz wave-absorbing material in the 0.1-1-THz range. This absorbing material is the world's thinnest high-performance terahertz wave-absorbing film, which can be used in sixth generation (6G) mobile communication systems and other applications.
Provided by the University of Tokyo
The surface-coated lambda trititanium pentoxide synthesized in this study uses conductive lambda trititanium pentoxide (λ-Ti3O5), which was discovered by Ohkoshi and his colleagues in 2010. Its surface is coated with insulating titanium oxide (TiO2) nanoparticles.
Lambda trititanium pentoxide is a titanium oxide material with a new crystal structure that exhibits metallic properties. Ohkoshi and his colleagues discovered various phase-transition phenomena between lambda trititanium pentoxide and beta-type trititanium pentoxide (β-Ti3O5), including light-induced, pressure-induced, and current-induced phase transitions.
The synthesized surface-coated lambda trititanium pentoxide exhibits a high dielectric loss tangent of 0.76 in the 0.1-1-THz range when measured using terahertz time-domain spectroscopy. This is due to extremely high dielectric loss occurring in the terahertz wave band caused by electron scattering at the domain interfaces inside the lambda trititanium pentoxide crystal and at the interfaces between insulating titanium dioxide nanoparticles and lambda trititanium pentoxide crystal.
The joint research team developed an ultrathin terahertz wave-absorbing film using this synthesized material based on theoretical calculations. This is an extremely thin film with a thickness of 48 µm, and it exhibits an excellent reflection loss (equivalent to 99.8% absorption) of −28 dB (decibel) at 0.77 THz. Such a terahertz wave-absorbing film in the 0.1-1-THz wave band has not been reported until now, and it is the thinnest in the world. In addition, the film demonstrates heat resistance, light resistance, water resistance, and organic solvent resistance, making it suitable for use in outdoor environments and under harsh conditions.
The raw material, lambda trititanium pentoxide, can be synthesized simply by firing a mixture of titanium dioxide and acetylene black and can be mass produced. Mass production costs can also be restricted to few hundred yen per square meter of the absorbing film; therefore, it is expected to be put to practical use. Surface-coated lambda trititanium pentoxide is an environmentally friendly material composed of titanium and oxygen atoms; therefore, it is also consistent with the Sustainable Development Goals (SDGs).
Because terahertz waves in the 0.1-1-THz range can achieve faster wireless communications, higher capacity, lower latency, and simultaneous connection of multiple devices, such waves in the 0.1-0.45-THz range are expected to be the carrier for 6G communications that will be deployed in the future. In addition to this, their various applications have been proposed, including noncontact vital monitoring systems, quality inspection scanning systems using tomographic imaging, and security sensing technology for hazardous material detections.
Astronomical telescopes using terahertz waves (up to 0.95 THz) have contributed to the observation of galaxies and the universe. In such applications of terahertz waves, it is extremely important to absorb unnecessary electromagnetic noise to ensure information security, avoid electromagnetic interference, and improve communication accuracy and sensitivity. However, films that absorb waves above 0.3 THz have not yet been put to practical use.
The joint research team expects that the newly developed thin terahertz wave-absorbing film will contribute to developing terahertz technology via its installation on covers (radome structures) and substrates for 6G antennas, noncontact vital monitoring systems, quality inspection scanning systems, radio telescope facilities, vehicle bodies, roads, and guardrails.
Journal Information
Publication: ACS Applied Materials & Interfaces
Title: Ultrathin Terahertz-Wave Absorber Based on Inorganic Materials for 6G Wireless Communications
DOI: 10.1021/acsami.4c17606
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.