Graphene’s “Big Tent” Drums.

Graphene’s “Big Tent” Drums"Normally, to make a graphene quantum dot, you would have to cut out a nanosize piece of graphene," says NIST fellow Joseph Stroscio. "Our work shows that you can achieve the same thing with strain-induced pseudomagnetic fields. It's a great result, and a significant step toward developing future graphene-based devices."

Drumroll please. About a week ago, scientists at the National Institute of Standards and Technology (NIST) and the University of Maryland published their work that looks likely to lead to beyond the next generation semiconductors, quantum dot semiconductors. While this is likely to be more of a next decade than this development, it sets the next decade up to be a great leap forward decade of technology advancement.

Below, the development covered earlier in this blog that deserves a little more publicity.  There is now so much diverse potential in our newly emerging graphene/nano-carbon age, that the trick is in making sure that we develop enough global graphite supply to sustain it, especially next decade. 1932s airplanes were nothing like 1912s, and I suspect that is the type of change we are embarking on, except faster, and in nearly all areas of modern life.

'Tuning' Graphene Drums Might Turn Conductors To Semiconductors
June 27, 2012
Tightening or relaxing the tension on a drumhead will change the way the drum sounds. The same goes for drumheads made from graphene, only instead of changing the sound, stretching graphene dramatically alters the material's electrical properties. Researchers working at the National Institute of Standards and Technology (NIST) and the University of Maryland have shown* that subjecting graphene to mechanical strain can mimic the effects of magnetic fields and create a quantum dot, an exotic type of semiconductor with a wide range of potential uses in electronic devices.

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—- The research team suspended a sheet of graphene over shallow holes in a substrate of silicon dioxide—essentially making a set of graphene drumheads. In probing the drumheads with a scanning probe microscope, they found that the graphene rose up to meet the tip of the microscope— a result of the van der Waals force, a weak electrical force that creates attraction between objects that are very close to each other. Calculations by the University of Maryland group showed that the graphene should stretch into a peak, like the top of a circus tent.

The researchers discovered that they could tune the strain in the drumhead using the conducting plate upon which the graphene and substrate were mounted to create a countervailing attraction and pull the drumhead down. In this way, they could pull the graphene into or out of the hole below it.
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Graphene Drumheads Tuned to Make Quantum Dots
June 21, 2012
—- The researchers discovered that they could tune the strain in the drumhead using the conducting plate upon which the graphene and substrate were mounted to create a countervailing attraction and pull the drumhead down. In this way, they could pull the graphene into or out of the hole below it.

And their measurements showed that changing the degree of strain changed the material's electrical properties.

For instance, the group observed that when they pulled the graphene membrane into the tent-like shape, the region at the apex acted just like a quantum dot, a type of semiconductor in which electrons are confined to a small region of space.

Creating semiconducting regions like quantum dots in graphene by modifying its shape might give scientists the best of both worlds: high speed and the band gap crucial to computing and other applications.
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