On ultra-fast carbon memory

Nanotubes

New types of computer memory using carbon - rather than silicon - offer the potential to create ultra-fast non-volatile memory.

High performance non-volatile memory (NRAM) is important for the computer industry because it opens up the possibility of computers booting up without a tedious wait. The technology also has applications in everything from flash memory to MP3 players and digital cameras.

A number of approaches to the problem have been suggested. Magnetic RAM, backed by IBM and Motorola, polymers and metal alloys (chalcogenides which change shape when electrically charged) have all been suggested.

The Economist reports on a new entrant to the field.

Massachusetts-based firm Nantero is backing the idea of using nanotubes, a cylindrical array of carbon atoms whose diameter is only about one nanometre (a billionth of a metre), as the building blocks of computer memory.

Nantero's design for NRAM "involves the use of suspended nanotube junctions as memory bits, with the 'up' position representing the bit zero and the 'down' position representing the bit one", the company explains.

"Bits are switched between states by the application of electrical fields," it adds.

Nantero's fabrication method involves "depositing a very thin layer of nanotubes over a wafer, and then using lithography and etching to remove the elements that are not in the correct position to serve as elements of the array".

This month the company announced it had used its patent-pending techniques to deposit an array of ten billion suspended nanotube junctions on a single silicon wafer.

Dr Thomas Rueckes, chief scientific officer at Nantero, said that its technique overcomes the problem of growing nanotubes in large arrays. He says that arrays larger than 10Gb are possible and the technique is chiefly limited only by the resolution of lithography equipment.

Nantero isn't the only firm working in the field. Last year, a team of researchers led by Phaedon Avouris at IBM's TJ Watson Research Centre in New York state made nanotube transistors that outperform state-of-the-art silicon devices, according to a recent New Scientist report.

Semiconducting nanotubes are far smaller, and therefore more efficient and faster, than their semiconductor equivalents.

It remains an issue to produce nanotubes cheaply.

However Nantero's work seems like a significant advance in fabricating nanotubes into electronic components.

The Economist reports that Nantero's new prototype memory "can read or write a bit in as little as half a nanosecond (billionth of a second)". That's twenty times faster than the performance possible with the best RAM chips currently available, the magazine notes.

Nantero told The Economist that it plans to have chips on the market "within a year". That's possible because the fabrication techniques it uses are based on an advancement of existing semiconductor-making technology, the company says. ®