UNIST Develops New Metasurface Allowing Terahertz Waves for 6G Communication!

Meta-surface fabrication process.

[Asia Economy Yeongnam Reporting Headquarters, Reporter Hwang Doo-yeol] An active material for the transmission channel of 6G mobile communication, capable of transmitting 1 trillion bits per second, has been developed.

The Nano-Optics Laboratory of the Department of Physics at UNIST created a new metasurface by patterning vanadium dioxide (VO₂) into a slit array, which maintains transparency over a wide terahertz (THz) range while allowing control of electrical conductivity.

A metasurface is a two-dimensional material engineered to have properties not found in nature. The newly developed metasurface possesses characteristics suitable for use as a device in 6G communication.

Vanadium dioxide is a material known for its temperature-dependent phase change near room temperature (67℃).

It can become a metal that conducts electricity well or an insulator that does not conduct electricity, making it promising for use as an active metasurface device.

Due to these properties, many research groups worldwide are striving to advance patterning technology that creates devices by patterning vanadium dioxide.

However, existing vanadium dioxide thin film patterning methods rely on ‘reactive ion etching (RIE)’, which can cause damage, or ‘drop casting’, which has poor reproducibility, presenting limitations.

Professor DaeSik Kim, Department of Physics, UNIST.

The UNIST Nano-Optics Laboratory devised a method utilizing photolithography, a semiconductor process that patterns materials with light.

After creating a vanadium metal pattern by photolithography, vanadium dioxide is grown through thermal oxidation by heating and reacting with oxygen in the air.

This method enables large-area vanadium dioxide patterning free from etching damage.

The research team fabricated a vanadium dioxide metasurface with a slit array structure having a period smaller than the terahertz wavelength, realizing a terahertz transparent electrode with electrically tunable properties.

By varying the temperature from room temperature to 100℃ and measuring optical and electrical properties, they found that the conductivity of the vanadium dioxide region changed by thousands of times.

Meanwhile, the broadband transmittance of the metasurface terahertz wave remained consistently high and transparent even during the phase transition.

Professor Deok-Hyung Lee of the Department of Physics at UNIST, the principal investigator, said, “When vanadium dioxide is in the insulating state, it has a refractive index similar to that of the sapphire substrate, resulting in high transmittance. When it changes to a metallic state, the light concentrated in the slits compensates for the reduced transmittance in vanadium dioxide, maintaining high transmittance.”

The research team also confirmed that near-infrared (NIR) light transmitted through the metasurface can be selectively modulated according to the state change.

This demonstrates the potential for applications across multiple spectra.

First author Hyosim Yang, a doctoral researcher at Seoul National University, said, “The multifunctional terahertz variable transparent electrode developed in this study can be used in multi-spectral applications such as terahertz and near-infrared hybrid communication. The etching-free patterning process will be useful for mass production of vanadium dioxide-based metasurfaces.”

Supported by the National Research Foundation of Korea, the study was published online on August 7 in the world-renowned optics journal, Laser & Photonics Reviews.

(From left) Professor Lee Deok-hyung of UNIST, Yang Hyo-sim, PhD candidate at Seoul National University, Professor Kim Seong-hwan.

This content was produced with the assistance of AI translation services.