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Room-temperature terahertz device opens door to 6G networks

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Room-temperature terahertz device opens door to 6G networks


Assistant Professor Shigehisa Shibayama (right) and first author Shota Torimoto (left), along with the rest of the team, have developed a resonant tunneling diode using only non-toxic Group IV semiconductor materials that operates at room temperature. Credit: Shigehisa Shibayama (Nagoya University) and Shota Torimoto (Nagoya University)

In a world first, researchers at Nagoya University in Japan have successfully developed a resonant tunnel diode (RTD) that operates at room temperature made entirely from Group IV semiconductor materials.

The development of an RTD that operates at room temperature means the device could be deployed at scale for next-generation wireless communication systems. The use of only non-toxic Group IV semiconductor materials also supports more sustainable manufacturing processes.

This research marks a pivotal step toward terahertz wireless components that deliver unprecedented speed and data handling capacity with superior energy efficiency.

“Compared to InGaAs-based Group III-V RTDs that include toxic and rare elements, such as indium and arsenic, Group IV compounds-based RTDs are safer, lower cost, and offer advantages for creating integrated ,” said senior author Dr. Shigehisa Shibayama from the Nagoya University Graduate School of Engineering.

The results are published in the journal ACS Applied Electronic Materials.

Terahertz waves and quantum devices

Researchers have long struggled to achieve the high-speed and large-volume data transfer needed for sixth-generation (6G) cellular networks.

One promising solution is wireless communication using —electromagnetic waves that vibrate a trillion times per second, enabling ultra-high-speed data transmission. However, many remain before this technology can be made practical for consumer applications.

A critical component for realizing terahertz communication is the RTD. This quantum device operates through negative differential resistance, a counterintuitive property where increasing voltage actually decreases current. When part of a properly designed circuit, this property allows the diodes to sustain high-frequency oscillations that would otherwise decay due to electrical losses.

Room-temperature terahertz device opens door to 6G networks
The illustration (left) shows the different layers of the double-barrier structure; the two GeSiSn barriers are stacked between layers of GeSn. The table (right) indicates the layers where hydrogen gas was introduced in different scenarios. Credit: Shigehisa Shibayama (Nagoya University)

Moving beyond laboratory constraints

The secret behind an RTD lies in its double-barrier structure, where electrons or holes tunnel through layers of different , each only a few atoms thick. These layers have mainly been created from InGaAs-based Group III-V materials that include toxic and rare elements, such as indium and arsenic.

In previous research by the same group, the researchers created a p-type RTD using only Group IV materials, specifically germanium-tin (GeSn) and germanium-silicon-tin (GeSiSn) alloys. One limitation was that the diode only functioned at extremely low temperatures, around -263°C. Since and wireless systems cannot practically reach this level of cooling, the device would have remained a laboratory curiosity.

Shibayama and his colleagues have now discovered how to use only Group IV materials to produce a p-RTD that functions at room temperatures of around 27°C. This significant improvement opens new possibilities for the widespread adoption of terahertz semiconductor devices.

Room-temperature terahertz device opens door to 6G networks
The scenario (blue) where hydrogen gas was introduced to only the three GeSn layers exhibited superior crystallinity and homogeneity. Credit: Shigehisa Shibayama (Nagoya University)

The research group achieved its breakthrough by introducing hydrogen gas during the layer formation process. They tested three different scenarios:

  1. introducing hydrogen gas to both the two GeSiSn layers and three GeSn layers
  2. introducing no hydrogen gas
  3. introducing hydrogen gas to only the three GeSn layers.

In the last scenario, restricted island growth and mixing between layers, resulting in a smooth and well-ordered double-barrier structure.

“The RTD cannot function if these layers are mixed,” said Dr. Shibayama.

“If there are defects in the layers, electrons can tunnel through these easier routes, leading to current leakage. This leakage current needs to be reduced for negative differential resistance—the key property of an RTD—to occur.”

More information:
Shota Torimoto et al, Room-Temperature Operation of Ge1–xSnx/Ge1–x–ySixSny Resonant Tunneling Diodes Featured with H2 Introduction during Molecular Beam Epitaxy. ACS Applied Electronic Materials (2025). DOI: 10.1021/acsaelm.5c01049

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Room-temperature terahertz device opens door to 6G networks (2025, September 17)
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Ceramic material pair could unlock potential of safer, longer-lasting solid-state batteries

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Ceramic material pair could unlock potential of safer, longer-lasting solid-state batteries


Zirconia-enhanced electrolyte (left) avoids cracking seen in the baseline sample (right). Credit: David Mitlin

A team of four universities and three national laboratories, led by The University of Texas at Austin, developed a new approach for solid-state batteries, improving their performance while reducing the manufacturing costs. Solid-state batteries are an emerging energy storage technology that could unlock enhanced performance for drones, electronics and electric vehicles.

“The biggest game in town for next-generation batteries is making them all solid-state, allowing for improved safety and higher energy,” said David Mitlin, professor in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering and the lead investigator on the new research published in Nature Materials. “However, much more work is needed before all solid-state batteries may be widely commercialized.”

Today, most use an organic liquid , a maple-syrup-like substance that allows lithium ions to reversibly shuttle back and forth inside the battery. Despite being technologically mature, liquid electrolytes are the hydrocarbon “fuel” in the oft-reported battery fires.

Solid, ceramic-based electrolytes reduce fire risks, eliminating the hydrocarbon fuel that sustains battery thermal runaway reactions. However, ceramic electrolytes face their own hurdles, including high costs, challenging quality control during manufacturing and premature failure due to metal filament (termed dendrite)–induced short-circuiting.

Oxide ceramics based on the garnet structure are key materials for all . Garnet’s unique structure allows lithium ions to move quickly and efficiently, making it ideal for energy storage. But even garnet has struggled to overcome the dendrite problem, which is directly linked to the formation of small cracks inside the electrolyte.

Like a jeweler refining a gemstone, the researchers have polished the garnet to reveal its full potential. Dispersing micro-scale zirconia particles throughout the garnet grains suppresses both the cracking and the dendrites.

This method is based on carbide additives, which exothermically decompose during fabrication, inputting additional heat into the synthesis reaction. This creates an additional benefit of reducing the manufacturing cost by lowering the external temperature needed for processing.

“Zirconia really pulls double duty here,” said Yixian Wang, postdoctoral researcher in Mitlin’s lab, who is the co-lead author. “It helps densify the material while also preventing those pesky lithium dendrites from forming. It’s a win–win for battery performance and safety.”

In tests, the zirconia-modified garnet achieved nearly double the critical current density—the maximum current it can handle before short-circuiting—compared to unmodified garnet. This means batteries using this material can operate at higher power levels without compromising safety.

While battery science is the driving force of this research, the results may be applied to a wide variety of manufacturing sectors for high-quality ceramics, where defect control is essential.

More information:
Vikalp Raj et al, Grain boundary zirconia-modified garnet solid-state electrolyte, Nature Materials (2025). DOI: 10.1038/s41563-025-02374-9

Citation:
Ceramic material pair could unlock potential of safer, longer-lasting solid-state batteries (2025, November 4)
retrieved 4 November 2025
from https://techxplore.com/news/2025-11-ceramic-material-pair-potential-safer.html

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It’s Been a Year Since Trump Was Elected. Democrats Still Don’t Get the Internet

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It’s Been a Year Since Trump Was Elected. Democrats Still Don’t Get the Internet


After losing big in 2024, Democrats promised a digital reckoning.

But 12 months out from that devastating slate of losses, Democratic digital programs are still plagued by the same issues that doomed them last year. Despite millions of dollars in influencer investments and “lessons learned” memos, party insiders say Democrats are still stuck running social media programs that strive for authenticity, but often clash with the party’s unrelenting desire to maintain control.

“I can’t, for the life of me, figure out why we are still so rigid and moderating everything when we have nothing to lose for the first time,” says one Democratic digital strategist, who requested anonymity to speak candidly. “All of the threats of fascism and right-wing takeover. It’s all here.”

This aversion to risk has made it difficult for Democrats to innovate. In June, the Democratic National Committee launched a new YouTube show called The Daily Blueprint. In a statement, DNC chair Ken Martin said that the show—which runs news headlines and interviews with party officials in an attempt to be MSNBC-lite—“cements our commitment to meet this moment and innovate the ways we get our message across a new media landscape.”

The show, hosted by DNC deputy communications director Hannah Muldavin, has brought in only around 16,000 views total across more than 100 episodes since its launch.

“We’re focused on reaching as many people as possible, and we’ve made huge progress this year in expanding our reach,” a spokesperson from the DNC tells WIRED. “Since January, the DNC has seen enormous follower growth on high-traffic platforms like TikTok and Instagram, accruing over 3.8 billion impressions across our accounts. We are building relationships with hundreds of creators so that the Democratic Party is a constant presence on voters’ feeds, cutting across interests and backgrounds. We’re investing now in building an innovative digital program that will continue to grow cycle after cycle.”

But to some Democratic strategists, The Daily Blueprint is emblematic of how the party continues to promote its least effective digital communicators. Since the government shut down earlier this month, Senate minority leader Chuck Schumer has hosted a string of highly-produced videos that have barely registered outside of the Washington, DC, ecosystem. “If you are not willing to take swings or throw shit against the wall in this moment, then when are you going to do that?” says Ravi Mangla, the national press secretary for the Working Families Party, a small progressive party already critical of the Democratic National Committee. (Schumer’s Senate office did not immediately respond to a request for comment.)

Younger Democratic operatives say the issue stems from a broader culture of gatekeeping not just who is allowed to speak on behalf of the party, but what the content coming out of official channels looks like. The people approving content are “not young people and they’re not posters,” says Organizermemes, a creator and digital strategist. “They can’t explain why things [online] went well. Their ‘theory of mind’ is often fundamentally wrong because they don’t engage with the actual doing of it.”



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UV light holds promise for energy-efficient desalination

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UV light holds promise for energy-efficient desalination


How ultraviolet light, emitted through aluminum nitride (AIN-OH), may break bonds between salt and water. Credit: UCR/Singh et al. ACS Applied Materials & Interfaces (2025). DOI: 10.1021/acsami.5c12331

A team of UC Riverside researchers has uncovered a potential breakthrough in solar desalination that could reduce the need for energy-intensive saltwater treatment.

Led by Luat Vuong, an associate professor of mechanical engineering in UCR’s Marlan and Rosemary Bourns College of Engineering, the team has demonstrated for the first time how the highest frequencies of sunlight—specifically invisible ultraviolet (UV) light—can break the stubborn bonds between salt and water.

“To our knowledge, nobody else has yet articulated this deep UV channel for salt-water separation,” Vuong said. “UV light in the of 300–400 nanometers is used for disinfection, but this deep UV channel, around 200 nanometers, is not well known. We may be the first to really think about how you can leverage it for desalination.”

While much work remains before practical applications are developed, the discovery provides a clear path for further research and innovation.

Published in ACS Applied Materials & Interfaces, the study by Vuong and her colleagues details how the team made a wick from aluminum nitride—a hard, white ceramic—to separate salt from water by harnessing specific light wavelengths that interact with salt water without heating the bulk liquid.

Unlike traditional solar desalination methods, which rely on dark materials to absorb heat and boil water, Vuong’s approach could bypass the need for altogether.

The experiments involved placing pairs of ceramic wicks in an enclosed chamber, with each allowed to equilibrate or adjust to similar environmental conditions. Under UV light, evaporation rates of salt water increased significantly compared to control samples kept in the dark or exposed to red, yellow, or infrared light.

“Aluminum nitride is well suited for emitting UV light due to its ,” Vuong explained.

The material may be triggering a process called “photon upconversion,” in which low-energy photons combine into a single high-energy photon. That upconverted photon delivers a more powerful punch, potentially strong enough to break the salt-water bonds.

If this upconversion process occurs without generating excess heat, which is yet to be determined, the approach could offer a non-photothermal alternative to traditional solar desalination systems that boil or heat salt water to produce vapor, which then condenses into fresh water.

Such solar systems also could reduce the heavy electricity demands of reverse osmosis systems, which use high-pressure pumps to force salt water through membranes. The system could also address the concentrated reverse-osmosis brine waste, which is toxic to marine life when discharged into waterways.

Other potential applications for the wicking approach may be for other waste management processes, harvesting minerals in , or replacing “swamp” coolers with evaporation systems.

Still, Vuong emphasized that further research is needed before aluminum nitride-based solar desalination systems can be engineered for widespread use.

“Other materials may be designed to be just as effective, but is practical. It is inexpensive, widely available, non-toxic, highly hydrophilic, and durable,” Vuong said.

Moving forward, Vuong’s group is designing system architectures, fabrication processes, and spectroscopic tools to better understand and enhance light-driven evaporation.

More information:
Navindra Singh et al, Spectrum Selective Interfaces and Materials toward Nonphotothermal Saltwater Evaporation: Demonstration with a White Ceramic Wick, ACS Applied Materials & Interfaces (2025). DOI: 10.1021/acsami.5c12331

Citation:
UV light holds promise for energy-efficient desalination (2025, November 4)
retrieved 4 November 2025
from https://techxplore.com/news/2025-11-uv-energy-efficient-desalination.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.





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