Researchers integrate diamond/boron nitride crystalline layers for use in high-power devices

Materials researchers at North Carolina State University have developed a new technique to deposit diamond on the surface of cubic boron nitride (c-BN), integrating the two materials into a single crystalline structure.

"This could be used to create high-power devices, such as the solid state transformers needed to create the next generation 'smart' power grid," says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of a paper describing the research.

"It could also be used to create cutting tools, high-speed machining and deep sea drilling equipment," Narayan says. "Diamond is hard, but it tends to oxidize, transforming into graphite – which is softer. A coating of c-BN would prevent oxidation. Diamond also interacts with iron, making it difficult to use with steel tools. Again, c-BN would address the problem."

C-BN is a form of boron nitride that has a cubic . It has similar properties to diamond, but holds several advantages: c-BN has a higher bandgap, which is attractive for use in high-power devices; c-BN can be "doped" to give it positively- and negatively-charged layers, which means it could be used to make transistors; and it forms a stable oxide layer on its surface when exposed to oxygen, making it stable at high temperatures. Earlier this year, Narayan unveiled a faster, less expensive technique for creating c-BN.

To create the epitaxial, or single crystal, diamond/c-BN structures, the researchers begin by creating a substrate of c-BN. This is done using the new technique Narayan published earlier this year. They then use a process called pulse-laser deposition – which is done at 500 degrees Celsius and an optimized atmospheric pressure – to deposit diamond on the surface of the c-BN. The pulse-laser technique allows them to control the thickness of the diamond layer.

"This is all done in a single chamber, making the process more energy- and time-efficient," Narayan says. "You use only solid state carbon and BN, and it's more environmentally benign than conventional techniques."

The researchers were also able to deposit diamond on the c-BN using the conventional technique, which utilizes methane gas, hydrogen gas and a tungsten filament at 900 °C.

"The chemical vapor deposition approach works, but our pulsed laser deposition approach works much better, doesn't involve toxic gases, and can be done at much lower temperatures," Narayan says.


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Researchers discover new phase of boron nitride and a new way to create pure c-BN

More information: Jagdish Narayan et al. Direct conversion of h-BN into c-BN and formation of epitaxial c-BN/diamond heterostructures, Journal of Applied Physics (2016). DOI: 10.1063/1.4948688
Journal information: Journal of Applied Physics

Citation: Researchers integrate diamond/boron nitride crystalline layers for use in high-power devices (2016, May 10) retrieved 22 August 2019 from https://phys.org/news/2016-05-diamondboron-nitride-crystalline-layers-high-power.html
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May 13, 2016
Sub; Triggered Space exploration
CVD and laser deposition-deposit diamond on the c-BN -appears to be good advancement. I can suggest space propulsion techniques.Space Cosmology vedas interlinks -best of brains trust


May 14, 2016
These high-power transistors can be used in switching power converters to handle the currents necessary to enable higher efficiency for converting power from storage to line levels for better renewable energy usability at times when the wind isn't blowing and the Sun isn't shining.

Meanwhile, integrating diamond with metal allows the formation of new subtractive machine tools that have better wear characteristics and make more precise parts.

There's a lot of value from this research.

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