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A Diamond is a Diamond... until It's Very Small

 Diamondoids show promise for super efficient electronics

(Photo - Jeremy Dahl)
Diamondoids researcher Jeremy Dahl.
(Photo by Kelen Tuttle.)

In a basement lab on the Stanford University campus, Jeremy Dahl pulls out a vial of what looks like fine white powder.

"Here they are," he says with a grin, tilting the vial back and forth.

The powder is actually a pile of miniscule diamonds, or diamondoids. The tiny gems are so small that even the big ones are measured only in micrometers—millionths of meters. But if researchers with the Stanford Institute of Material and Energy Science are successful, diamandoids could become a lot bigger, showing up in everything from home electronics to pharmaceuticals.

Right now, Dahl is one of the only people in the world who can produce diamondoids, making SIMES the nexus of diamandoids research. The program got a big boost last July, when SIMES researcher Nick Melosh received a $2.5 million Department of Energy Single Individual and Small Group Research grant to study the properties and potential applications of the materials.

Diamonds are composed of cages of interlocking carbon atoms. While a carbon atom at the center of a diamond is bound to four other carbon atoms, a carbon atom at the diamond's surface is bound to only three, with exposed space filled by a hydrogen atom. As the size of the diamond decreases into the micrometer range, the ratio of hydrogen atoms to carbon atoms increases, eventually altering the behavior of the material.

As a result, diamondoids have some interesting properties—aside from being tiny, they’re extremely resilient and emit electrons extremely efficiently. But they’re also fairly customizable, meaning different kinds of diamondoids can be produced to meet different specifications: three-dimensional crystals for applications requiring a powdered material, two-dimensional films for coating other materials, and possibly even one-dimensional nano-wires for transferring charge or light.

"Scientifically, diamondoids are very, very nice because you can tune them," Melosh said.

The combination of tunability and easy electron emission makes diamondoids ideal for a number of applications. For example, because they are excellent conductors, transmitting heat quickly and efficiently, diamondoids could possibly be used to dissipate heat from computer components, helping to keep them within safe operating temperatures.

Diamondoids could also help enable the production of super vibrant next generation displays that, like organic light emitting diode displays, would be able to create high resolution images using carbon-based nanomaterials. Electrical current streamed into a diamondoid is transferred into brilliant light. Because diamondoids—like diamonds—don't absorb light, instead transmitting it faithfully, a diamondoid-based television screen would display very clear colors and an intense picture.

SIMES researchers are also looking at ways to make this process work in the reverse—streaming photons into the diamondoids to generate an electrical current. If they perfect the process, it could pave the way for a new generation of super-effective solar panels.

"I sort of consider diamondoids to be LEGOs for grown-up scientists," Dahl said. This is just the beginning of what we can do with them."

—Nicholas Boch and Olga Kuchment
  SLAC Today, April 29, 2010