US Developed Diamond/Boron Nitride Crystal Layer Used for High Power Devices

Recently, materials researchers at North Carolina State University have developed a kind of new technology - depositing diamond on the surface of cubic boron nitride (c-BN), to combine into a new single crystal structure.

"This kind of material can be used to make high power devices, such as creating the solid state transformer that next generation smart grid needs." says Jay Narayan, a distinguished professor and the main author of this paper from Materials Science and Engineering in North Carolina State University.

"It can also be used to make knives, high speed machining and deepwater drilling equipment," says Narayan."Diamond is very hard, but is also easily oxidized into soft graphite. The c-BN cladding layer can prevent oxidation. Diamond also interacts with iron, which can make it difficult used for steel tool. Again, the c-BN will solve the problem."

The c-BN is boron nitride (BN) with cubic crystal structure. It has similar performance with diamond, but has several advantages: The c-BN has higher band gap, which makes it attractive when it is used for power devices; The c-BN can be "mixed", obtaining positive and negative charge, which means it can be used to make the transistor; When it is exposed to oxygen, the surface will form stable oxide layer, which will make it stable under the condition of high temperature. Earlier this year, Narayan announced a faster and cheaper manufacturing technology of c-BN.

First of all, researchers create the c-BN substrate, used to create extension, or single crystal diamond/c-BN structure. It adopts the new technology released by Narayan earlier this year. Then it needs to use pulsed laser deposition, to deposit diamond on the surface c-BN under 500 ℃ and the optimization of atmospheric pressure. The use of pulse laser technology can help to control the thickness of diamond layer.

"It can finish all the work just in a single cavity, and the process is more energy-efficient and more timely," says Narayan. "Just using solid carbon and boron nitride is OK. It has more environmental protection than the traditional technology."

Researchers will also be able to use the traditional chemical vapor deposition technology to deposit diamond on the surface of c-BN, but it needs to use methane gas, hydrogen and 900 ° c of tungsten filament.

"Chemical vapor deposition can finish the work, but our pulsed laser deposition method has better effect. It not only involves toxic gas, but also can be finished at low temperature."Narayan says.

Narayan has founded a company with others - Q - carbon Co., LTD. This company has got the authorization of the the technology, engaged in the commercial use of this technology in multiple applications.