CNT-based 'NRAM' Shows Potential as Universal Memory

2014/06/13 23:46
Jyunichi Oshita, Nikkei BP Semiconductor Research
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A Japanese research team and the US-based Nantero Inc verified that "NRAM," a new non-volatile memory using carbon nanotubes, has excellent properties and can be used for various applications ranging from main memory to storage.

They realized high-speed, low-power-consumption and high-reliability operation of memory cell by using a write method suited for NRAM. The Japanese team is led by Ken Takeuchi, professor at the Department of Electrical, Electronic and Communication Engineering, Faculty of Science and Engineering of Chuo University.

The details of the new technology were announced in a lecture titled "23% Faster Program and 40% Energy Reduction of Carbon Nanotube Non-volatile Memory with Over 1011 Endurance" (lecture number: T11-3) at 2014 Symposia on VLSI Technology and Circuits, which runs from June 9 to 13, 2014, in Honolulu, the US.

NRAM is a memory that Nantero has long been developing. Its memory cell consists of (1) a thin film made of many carbon nanotubes (CNTs) and (2) two metal electrodes sandwiching the film.

When a voltage is applied to the cell, CNTs, which are separate from one another, come close to one another because of electrostatic force and adhere to one another due to intermolecular force. Then, the number of conductive paths increases between the electrodes, lowering resistance value. Even when the voltage is lowered to zero, CNTs do not separate from one another because they are tightly attached to one another.

This phenomenon was applied to a non-volatile memory. When data is being replaced, a voltage higher than a writing voltage is applied. Then, a phonon (lattice vibration) is generated at the bonded parts of the CNTs, and the heat generated by the phonon separates the CNTs.

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