Smartphones

New Material Opens the Door to Next-6G Electronics

Jan. 9, 2020
A tunable dielectric that works at frequencies above 30 GHz solves one of the problems behind 6G.

Millions of cellphone users might not know it, but their phones rely on a small barium-strontium titanate (BST) part to tune into signals for clear reception. That’s all well and good, but researchers know that while today’s cellphones, including the newest 5G phones, operate at frequencies below 6 GHz, the next wave of 5G phones and anticipated 6G cellular communications will operate at frequencies above 30 GHz where BST doesn’t perform well.

Fortunately, a group of engineers at Cornell University has created a new tunable dielectric that will replace BST and bring this clarity and extra bandwidth to the next generation of cellphones and other high-frequency electronics.

“Our material gives the same performance you get in today’s cellphone material, at 100-times-higher frequencies,” says Darrell Schlom, the team leader, the team leader. “That’s a big deal because as you increase the frequency, you get more bandwidth and more data can flow. And people are hungry for data, especially on their cellphones.”

Back in 2013, the group used molecular beam epitaxy to create a layered strontium titanium oxide for a similar purpose. That insulator, also a tunable dielectric, boosted performance of circuit capacitors by up to about 40 GHz by removing the barium from BST.

The materials before were “lossy”, which means they wasted a lot of energy and turned it into heat rather than facilitating useful tuning of the antennae. Part of the reason for this can be traced to a mixture of barium and strontium atoms that were thrown in randomly. The group eventually learned that if they ordered the strontium and gave it a more definite structure, losses were reduced. And so this time, with Craig’s guidance, instead of throwing the atoms in randomly so they just fell anywhere, the researchers kept the two types of atoms in different layers to take away some of the randomness and remove the disorder. By doing so, they removed the losses and the power dissipation. The researchers then reintroduced barium in a carefully applied layer just one atom thick to their strontium titanium oxide dielectric through a technique called targeted chemical pressure.

The resulting material, with its small layer of barium, can operate at frequencies up to 125 GHz, well above the desired 30 GHz for the next wave of 5G and even 6G cell service. The tunable dielectric could also be used for defense applications such as electronic spoofing, in which a signal is deployed to confuse high-frequency radars.

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