"The applications would be an entirely new class of nanoelectronic devices," said lead researcher Prabhakar Bandaru, a materials scientist at the University of California, San Diego.

Modern computers work by encoding data as a series of ones and zeros. This code is conveyed via transistors, which are minute switches that can either be flicked on or off to represent a one or a zero.

The dramatic growth in the speed of electronics over time is due in large part to the steady drop in the size of transistors, which allows more and more to be crammed closer together. The problem: Shrinking the features of conventional electronics past 10 nanometers -- where distances are in the range of atoms -- is virtually impossible, because the electrons start to jump back and forth randomly. Based on Moore's law -- the chip industry's observed ability to double transistor density roughly every two years -- the 10-nanometer limit should arrive in roughly 15 years.

Scientists have experimented with carbon nanotubes in transistors for the last 10 years. Prior attempts employed the nanotubes as channels for electrical current, with a separate component known as a gate made of silica and silicon that switched the current on and off.

Bandaru and colleagues instead developed a carbon-nanotube transistor with the gate built into the device. They started with straight multi-walled nanotubes and mixed in iron-titanium particles that catalyzed the growth of additional tubes from the originals, much like branches from a tree.

The end results were Y-shaped carbon nanotubes, with the catalyst particles absorbed into the junction of the Y. The metal particle then acts like a gate. Applying a voltage to the stem of the Y from the outside, via 50-nanometer-wide platinum wires, charges the particles and stops the flow of electric current through the nanotube.

The scientists reports their findings in the September issue of the journal Nature Materials.

Bandaru said because less power going into the carbon nanotubes is lost as heat, compared to conventional transistors, it could allow packing them more tightly. That, coupled with their tiny size, could lead to more powerful computers.

In the future, the researchers plan to experiment with even more esoteric shapes.

"An X-junction can be made by laying a nanotube on top of another and fusing them together," Bandaru said. "The biggest question would be, 'Can one make a large scale integration scheme with billions of transistors just like our Pentium?' This is difficult at the present stage."

Lars Samuelson, of Lund University in Sweden, whose lab and that of Charles Lieber at Harvard University have developed branching semiconductor nanostructures, said "the control of the way the branched nanotubes are made is not at all so good at this stage, but if they can take care of that, this could have a very big impact."

Charles Choi covers research and technology for UPI Science News.

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