push and pull

Elastic diamonds could help quantum computers run at room temperature

Quantum computing could get a 10 karat upgrade.


Diamonds are about to have a new best friend.

Prized by jewelers for its hard exterior and sparkling interior, engineers also fancy them for their electronic properties. Now, scientists have found a way to grow diamonds in the lab that can be stressed and strained — without losing their shape — to give them special, electricity-conducting properties.

A hundred times thinner than a human hair, these stretchy diamonds can bend up to 10 percent its original shape before springing back — all at a balmy room temperature.

Why it matters — In addition to being tough, diamonds are highly conductive when it comes to both electricity and heat. By creating stretchy diamonds in the lab, the scientists hope to improve upon these features and get them into next-gen electronics — including quantum computer chips.

Their findings were published Thursday in the journal Science.

Here's the background — When it comes to designing electronics that are smaller, faster, and more efficient than their silicon-based counterparts, diamond-based materials are an engineer's "Mount Everest" — beautiful in theory, but extremely difficult in practice.

Part of the problem, explain the authors, is overcoming limitations in the material's crystalline structure, as well as optimizing its "figures-of-merit" — ironically, the characteristics that make it a good match for these future electronic systems.

Ju Li, a coauthor on the study and professor of Material Science and Engineering at the Massachusetts Institute of Technology, tells Inverse these properties "scale dramatically" with the material's "bandgap," which is a measure of energy.

"The bandgap is a convenient indicator of how much the physical properties of a well-known material can change with elastic strain," Li says.

Li's team sought to investigate whether placing strain on diamonds might change — and even further improve — these figures-of-merit, without the diamonds breaking or resisting the strain.

"This is an active field of research," Li says. "[But] strain engineering can be very powerful."

See also: "Super-Deep Diamond" reveals first discovery of rare earth mineral

In their new work, the researchers set out to test how much they could strain single-crystalline diamonds grown in their lab could sustain using something called a nanoindenter — essentially, a microscopic battering ram.

Diamonds are often associated with luxury and excess, but to engineers, these tough materials could be a breakthrough in microelectronics.Shutterstock

What they did — The team fabricated several diamond samples in the lab and used their tiny battering ram to see how they would respond to different levels of strain coming at them from different angles. They then used transmission electron microscopy to peer into the diamonds' crystalline structure, and see how they were changed by the assault.

What they discovered — After subjecting their tiny crystals to a fair amount of poking and prodding, the researchers found they could reliably achieve between 6.5 and 8.2 percent strain with full recovery of the form when pushed from three different directions. Overall, they observed a maximum strain of 9.7 percent, which the authors report is very close to the ideal elastic limit for a material like this.

Intriguingly, they found increased strain on these diamonds resulted in a corresponding decrease in internal energy — transforming them into a direct-bandgap superconductor — a characteristic which will ultimately play an important role in enabling these materials to be incorporated into microelectronic mechanical systems, including light or quantum-based electronics.

An image of the diamond samples being stretched to 6 percent before fracturing.Dang et al. / Science

What's next — Microelectronics based on these bendy diamonds won't be ready for prime-time any day soon, but the researchers believe the results from their paper demonstrate diamonds could usher in the transformation in how these electronics are made — and how fast they become accessible to consumers.

"Diamond is one of the most promising materials for high-frequency, high-power electronic devices, as well as photonics applications," Li says. "It is also an important quantum material."

Instead of silicon-based computer chips, quantum computers may have chips made of diamond instead, which would improve their thermal conductivity and ability to operate in temperatures above absolute zero — a notorious sticking point for quantum technologies.

In the future, Li says the team plans to investigate how this technology could be applied to renewable energy and storage as well.

Abstract: Diamond is not only the hardest material in nature, but is also an extreme electronic material with an ultrawide bandgap, exceptional carrier mobilities, and thermal conductivity. Straining diamond can push such extreme figures of merit for device applications. We microfabricated single-crystalline diamond bridge structures with ~1 micrometer length by ~100 nanometer width and achieved samplewide uniform elastic strains under uniaxial tensile loading along the, and directions at room temperature. We also demonstrated deep elastic straining of diamond microbridge arrays. The ultralarge, highly controllable elastic strains can fundamentally change the bulk band structures of diamond, including a substantial calculated bandgap reduction as much as ~2 electron volts. Our demonstration highlights the immense application potential of deep elastic strain engineering for photonics, electronics, and quantum information technologies.
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