Manufacturing Bits: May 17

Isolating diamondoids; diamond deposition; GaN-on-silicon.


Isolating diamondoids
Stanford and the SLAC National Accelerator Laboratory are finding new ways to isolate diamondoids.

Diamondoids, which are tiny specks of diamond, are found in petroleum fluids. The smallest diamondoid consists of 10 atoms. A diamondoid weighs less than a billionth of a billionth of a carat. A carat is a unit of mass equal to 200 mg.

Nano-scale diamondoid crystals (Source: SLAC)

Nano-scale diamondoid crystals (Source: SLAC)

Diamondoids could be used in several applications, such as energy, electronics, and molecular imaging.

To devise these materials, researchers went to a Chevron refinery in Richmond, Calif. Then, they analyzed crude oil from the Gulf of Mexico. From there, they found which oil had the highest concentration of diamondoids.

Then, crude oil was boiled in huge pots. Smaller batches were boiled again to evaporate and isolate the molecules. Fluids were then forced into a system through a filtration system. This, in turn, separated out the diamondoids.

Now, researchers are taking diamondoids and using them to help grow nano-sized diamonds in the lab. They have added other elements in the process, such as silicon or nickel. With the technology, researchers hope to produce single photons of light for next-generation optical communications and biological imaging.

Clumps of diamondoid crystals (Source: SLAC)

Clumps of diamondoid crystals (Source: SLAC)

Diamond deposition
North Carolina State University has developed a new technique to make power semiconductors and other products.

Using a technology called pulse-laser deposition, researchers can deposit diamond on the surface of cubic boron nitride (C-BN). In doing so, they have integrated the two materials into a single crystalline structure.

C-BN is the world’s second hardest material after synthetic diamond, according to Element Six. C-BN is a form of boron nitride that has similar properties to diamond. But c-BN has a higher bandgap than diamond, making it attractive for power devices, according to researchers. In addition, c-BN can be configured into a field-effect transistor.

In the lab, researchers devised a substrate of c-BN. Then, they used a technology called pulse-laser deposition. At a temperature of 500 degrees Celsius, pulse-laser deposition was used to deposit diamond on the surface of the c-BN.

Raman spectra from diamond/c-BN single crystal films (Source: NC State)

Raman spectra from diamond/c-BN single crystal films (Source: NC State)

Using this technique, researchers created a super undercooled state. As a result, researchers created a new state of BN, dubbed Q-BN. “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, on the university’s Web site.

“It could also be used to create cutting tools, high-speed machining and deep sea drilling equipment,” Narayan said. “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.”

Hoping to speed up the development of gallium-nitride (GaN) for power semiconductors, Imec has entered into a partnership with IQE, a supplier of epitaxial wafers and other products.

IQE will join Imec’s GaN-on-Si Industrial Affiliation Program. Imec, a Belgium-based R&D organization, has a 200mm gallium nitride-on-silicon process line.

The program is conducting R&D on GaN-on-Si epitaxy and enhancement mode device technologies on 200mm wafers. It involves research on novel substrates to improve the quality of epitaxial layers, new isolation modules to enhance integration levels, and advanced vertical device development.

GaN-on-Si technology is used for power devices. GaN technology offers faster switching-power devices with higher breakdown voltage and lower on-resistance than silicon, making it an ideal material for advanced power electronic components.

Wayne Johnson, head of IQE’s Power Business Unit, said: “The importance of GaN on Si for power devices cannot be understated, particularly as we enter an era of electrically propelled transportation and increasing demands for energy efficient power control systems that require high voltage and high power capabilities.”