Pushing Diamond To Its Limits

Similar to how pressure turns coal into diamonds, subjecting diamonds to large amounts of strain gives desirable electronic properties to the gem.

AsianScientist (Jan. 28, 2021) – For the first time ever, researchers from Hong Kong have demonstrated the uniform straining of miniature diamonds. Their results, published in Science, point to the possibilities of using these stretched diamonds in advanced technologies like microelectronics, photonics and quantum information technologies.

Well-known for its hardness, diamonds are typically used in industrial settings for cutting, drilling or grinding various materials. However, diamonds have also found a use in electronic and photonic, or light-based, devices due to its ultra-high thermal conductivity, ability to carry electric charges and ultra-wide bandgap.

In semiconductors, wide bandgaps—the minimum energy needed to excite an electron—enable the operation of high-power or high-frequency devices. However, diamond’s wide bandgap and tight crystal structure make the gem difficult to modify, or dope, during production. This limits the industrial application of diamonds in electronic devices.

In 2018, a team led by Dr. Lu Yang from the City University of Hong Kong discovered that nanoscale diamonds can be bent by applying large amounts of strain. Therefore, it should be possible to modify a diamond’s physical—and electronic—properties through strain engineering.

Putting their findings into practice in this study, Lu and his collaborators fabricated miniature single-crystal diamond samples. Bridge-like in shape, the samples were one micrometer in length and around 300 nanometers wide.

These tiny diamond bridges were then stretched and subjected to several cycles of applied strain, demonstrating a uniform and elastic deformation of about 7.5 percent across its whole length. Once the source of strain was unloaded, the diamond bridge quickly recovered its original shape.

By further optimizing the diamond’s properties, the researchers achieved a maximum strain of up to 9.7 percent. They also found that as the amount of applied strain increased, diamond’s bandgap generally decreased.

Interestingly, at strains larger than nine percent, the gem’s bandgap changed from indirect to direct—meaning that the electrons directly emit photons. For semiconductors, direct bandgaps are desirable as they allow for more efficient light-based electronics.

Ultimately, the team’s findings show that the diamond’s bandgap can be modified and more importantly, that these changes are reversible. Their results open the doors for diamonds to be widely used in diverse applications, ranging from transistors to light-based electronics and even quantum technologies.

“I believe a new era for diamond is ahead of us,” concluded Lu.

The article can be found at: Dang et al. (2021) Achieving Large Uniform Tensile Elasticity in Microfabricated Diamond.


Source: City University of Hong Kong; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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