Skip to comments.Electron beams shrink carbon nanotubes to order
Posted on 11/14/2006 8:33:13 PM PST by annie laurie
A way of controllably shrinking carbon nanotubes has been developed by US researchers. They say the technique could someday be used to make faster computers and other novel electronic devices.
Carbon nanotubes have been used to make a variety of different nanoscale electronic devices, including sensors and transistors. These can outperform conventional components, working at higher frequencies and sensitivities, thanks to the novel physical and electronic properties of nanotubes.
These properties, however, depend strongly on the dimensions of each tube. And, until now, there has been no reliable way to make nanotubes to order.
This means "nanotube device fabrication is an unpredictable process", says Alex Zettl, who developed the shrinking method with colleagues at the University of California at Berkeley and another team at Lawrence Berkeley National Laboratory, both in the US.
Made to measure
The shrinking technique can be used to compress a nanotube to a particular diameter, which could then in theory be used as particular types of electronic component.
The process begins with depositing a solution of nanotubes on top of a silicon wafer. A scanning electron microscope is used to select a tube to which a gold electrode can be easily attached to each end.
The shrinking begins when the wafer carrying this tube is loaded into a transmission electron microscope. An electron beam is fired at the tube, knocking carbon atoms out of their honeycomb arrangement within its walls and causing them to either crowd into other parts of the arrangement, disturbing the shape, or fall out altogether.
At the same time, a current is run through the tube, via the gold contacts, and this reshuffles the remaining carbon atoms back into a regular, albeit narrower, nanotube structure. The current also causes some atoms to form new bonds with others.
The researchers were able to gradually shrink a nanotube measuring 16 nanometres in diameter down to 3 nm using the technique, until finally it broke in two.
Nanotubes are the most intensively studied area of nanotechnology, says Peter Bøggild at the Technical University of Denmark. "But there appear to still be surprises out there," he adds. "This is impressive."
The tiny tubes can be created in the first place by depositing a carbon vapour or by blasting graphite with high energy lasers or electricity. Bøggild explains that chemically created tubes can be made different diameters but are especially prone to defects. On the other hand, tubes made from graphite have fewer defects but cannot be made to order.
"Being able to shrink nanotubes in such an orderly fashion might address that nicely," Bøggild told New Scientist. But he adds that the method employed by Zettl and colleagues will need some modification: "It is not going to be a manufacturing process it is not an easy experiment to do."
Journal reference: Nanoletters (10.1021/nl061671j)
A schizophrenic institution?
It is a not uncommon condition - many labs have medical wings, for instance, entirely dominated by liberals, and concurrent science wings, entirely dominated by conservatives. In fact, it is so common, it is almost axiomatic.
These guys have lots of time to figure this out....the software guys aren't sure how to move from using 2 cores to four....
In ten years they'll be puzzling over the change from 32 nano-cores to 64. ;')
My first Puter 35 years ago had 4 motors , a "quad 360" with the "new" MVS OS,, maybe IBM could help Redmond out on sequencing CP calls and memory management if Redmond hadn't shafted them on the development of OS/2 .