HP scientists make breakthrough in 'memristor' high speed storage technology

HP scientists have made a small breakthrough in the development of a next generation memory technology called memristors, which some see as a potential replacement for today's widely used flash and DRAM technologies.

In a paper published in the Nanotechnology journal, scientists report that they have mapped out the basic chemistry and structure of what happens inside a memristor during its electrical operation.

Previously, although working memristors had been built in the labs, scientists didn't know exactly what was happening inside the tiny structures. So while HP was already confident it could commercialise the technology, this discovery will allow it to greatly improve its performance, said Stan Williams, a senior fellow at HP.

"We were on a path where we would have had something that works reasonably well, but this improves our confidence and should allow us to improve the devices such that they are significantly better," he said.

Memristors were first described in 1971 by a professor at the University of California, Berkeley. Prior to that, scientists knew of only three basic circuit elements: the resistor, the capacitor and the inductor. Professor Leon Chua posited that there was a fourth.

Decades later, scientists at HP proved that memristors existed, and further proved that they could be made to switch back and forth between two or more levels of electrical resistance, which would allow them to represent the ones and zeros in digital computing.

Scientists knew that switching process was taking place but found it hard to study because memristors are so tiny. HP's latest breakthrough was to use highly focused X-rays to pinpoint a channel, just 100 nanometers wide, where the resistance switching takes place. A nanometer is about a millionth of a centimeter.

They then mapped out the chemistry and structure of that channel, and thus gained a better idea of how memristors operate. The paper was jointly published by HP and UC Santa Barbara.

The type of memory that can be built with memristors, called ReRAM, is non-volatile, which means devices can retain their data after the power supply is turned off. That's in contrast to DRAM, where the stored data is lost when the power is cut.

Williams estimated that HP's memristor technology could be commercially available by the middle of 2013, though "that's not an official promise from HP as a company," he said.

HP has built sample devices in its labs that should enable storage densities of 12Gbytes per square centimeter, Williams said That's using a 15-nanometer production process and a multi-level design, where four layers of memory cell are stacked on top of one another.

Memristors are one of several memory types being developed as potential replacements for flash and DRAM. As the memory cells on those chips get smaller with each manufacturing process generation, they are reaching certain physical limits that make it harder for scientists to keep squeezing out higher densities.

Flash is likely to reach its scaling limits first, and Williams estimated it has only one or two more process generations left, or about four years at most. DRAM has "a few more" generations left than Flash, he said.

But memory manufacturers could keep those process generations in use for longer than the 18 months to two years that is normal for each process generation today, he noted.