5 June 2009—A team of physicists led by Alex Zettl of the University of California, Berkeley, has created a carbon nanotube–based electromechanical memory device that they say can store bits safely for up to a billion years. Details of the advance, which is being acknowledged by independent experts as a breakthrough, will be reported in the 10 June issue of the journal Nano Letters .
Zettl and his colleagues constructed their memory device by taking an iron nanocrystal and placing it inside a hollow carbon nanotube. The iron particle is able to shuttle back and forth along the hollow cylinder, which provides a mechanism to create the 1 and 0 states required for digital bits. Electrodes are attached to the ends of the carbon nanotube, and the movement of the iron particle is controlled through the application of an electrical current. Writing information into the new memory cell is relatively easy, says Zettl. ”The real challenge was figuring out how to read out the device,” he says.
But measurements of the nanotube’s resistance suggested a way. ”There is a direct correlation between the nanoparticle’s position and resistance,” Zettl says. So reading the resistance, using pulses of current too puny to push the nanocrystal out of position, revealed the stored information.
Caroline Ross, a professor of materials science at MIT and an expert on memory technologies, is impressed. ”It is a very elegant demonstration of electrical write and read back of a nanomechanical device,” she says.
Zettl says that his team’s studies show that the memory cell has a storage capacity as high as 1 terabyte per square inch. But perhaps more unusual is that theoretical studies show that its bits are expected to persist for more than a billion years. ”At room temperatures, it is incredibly stable,” says Zettl.
Today’s common nonarchival memory technologies, such as flash memory, retain their data for decades at most. Archival technologies, such as magnetic tape and the humble ink on paper, should last hundreds of years.