Magnetised protein globules talk in binary code
Published: 26 Jul 2004 10:45 BST
Ribbons of nanotubes
Massachusetts-based Nantero has come up with a way to make transistors, the on-off switches inside chips, with carbon nanotubes, hollow tubes of carbon atoms that exhibit a number of remarkable properties.
The company's technology exploits two of these properties: the bendable nature of nanotubes and the strong attraction carbon atoms exhibit for one another.
In Nantero's memory design, ribbons of carbon nanotubes are suspended over pieces of carbon. In the "off" state, the ribbon of nanotubes does not touch the carbon. In the "on" state, the nanotube bends downward and then adheres to the carbon. Electricity flows and the memory cell registers as a 1, in data terms. An electric charge can separate or connect the ribbons.
Nantero's memory is faster than static random access memory (SRAM), an embedded form of memory used for caches on processors, chief executive Greg Schmergel said.
Nantero's success in licensing its technology -- LSI Logic and aerospace specialist BAE Systems have taken out licenses -- lie in a radical shift in architecture that was implemented during the past year. Initially, Nantero proposed making memory cells in which a single nanotube would connect or detach from a perpendicular nanotube below it.
While this would allow for incredibly dense memory chips, most analysts and scientists doubted that the company could come up with a way to erect millions of uniform, microscopic crossbars on a sliver of silicon less than a few square centimetres across.
In the new architecture of the company's chips, a layer of nanotubes is spread onto a piece of carbon. Engineers then use conventional lithography to "draw" electrical contacts that are connected to each other by the thick ribbons of nanotube material and the substrate. This method, however, eliminates many of the cost and size advantages, at least for now.
"We won't be achieving thousandfold density improvement just yet," Schmergel said.
And, like all other new memory advocates, the company will have to face the scepticism of an industry that has seen it all.
"A lot of people are looking for the next material, but we think they already found it in silicon," said Dan Steere, vice president of marketing and sales at Matrix Semiconductor.
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