Ten billion nanotubes

US based Nantero claims to have developed an array of ten billion suspended nanotube junctions on a single silicon wafer that it plans to use as the basis for a nonvolatile memory device.

‘The bit itself is not stored in the nanotube, but rather is stored as the position of the nanotube. Up is bit zero, down is bit one,’ explains Greg Schmergel, CEO and Co-Founder of the company. Bits are switched between states through the application of electrical fields.

‘It’s not at all an enormous problem to read the data out either,’ according to Schmergel. ‘You simply measure the resistance between the nanotube and the electrode below. If the nanotube is up, you obviously have a vastly different resistance than if the nanotube is down and touching the electrode. So the readout is quite robust since the difference between states is so large,’ he adds.

In the current ‘devices’, the bits stored are actually the result of the orientation of multiple nanotubes, not just one, although Schmergel says that it would be possible to do the job with just one as well.

To build the array of nanotubes, Nantero’s used a manufacturing method that involved depositing a very thin layer of carbon nanotubes over the entire surface of a wafer, and then using lithography and etching to remove the nanotubes that are not in the correct position to serve as elements in the array.

Dr. Thomas Rueckes, Chief Scientific Officer and Co-Founder of the company said that the manufacturing method solved the problem of growing nanotubes reliably in large arrays.

‘At the end of our process only the nanotubes in the correct positions are remaining,’ he said.

The present size of the array is 10Gbit, but the process could be used to make even larger arrays. The main variable now controlling the size is the resolution of the lithography equipment, according to Rueckes.

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