5 tech breakthroughs: Chip-level advances that may change computing

Laser-connected chips, flexible printed circuits, memristors and more are on the horizon.

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Novel circuits: Memristors

If your MP3 player is filling up with tunes but you feel like a cultural murderer every time you delete a song, memristor technology might be arriving just in time.

The first fundamentally new electronic component to appear since silicon transistors came on the scene in the 1950s, the memristor presents a faster, more durable and potentially much cheaper alternative to flash memory. And with about twice the capacity of flash chips, there's plenty of room for everything from Leonard Bernstein to Lady Gaga.

"If we were redesigning computer technology today, we'd use memristor memory," says R. Stanley Williams, senior researcher and head of the Quantum Science Research (QSR) group at HP Labs in Palo Alto, Calif. "It's the fundamental structure for the future of electronics."

The memristor -- basically a resistor with memory -- was first posited in 1971 by University of California, Berkeley, professor Leon Chua, but HP Labs' memristor prototypes weren't publicly demonstrated until 2008.

To build its memristors, HP uses alternating layers of titanium dioxide and platinum; under an electron microscope they look like a series of long parallel ridges. Below the surface is a similar setup at a right angle, producing a grid-like array.

memristor array
Alternating microscopic layers of titanium dioxide and platinum crossed over a similar layer produce a line of memristors.

"Think of it as a series of cubes that are 2 to 3 nanometers (nm) on a side," says Williams. (A nanometer is one-billionth of a meter, roughly one ten-thousandth the thickness of a human hair.)

The key is that any two adjacent wires can be connected with an electrical switch beneath the surface, creating a memory cell. By adjusting the voltage applied to the cubes, scientists can open and close tiny electronic switches, storing data like traditional flash memory chips. (See IEEE Spectrum's excellent 6-Minute Memristor Guide for more details from Williams about how memristors work.)

Called ReRAM, for resistive random access memory, these chips can store roughly twice the data as flash chips but are more than 1,000 times faster than flash memory and could last for millions of rewrite cycles, compared with the 100,000 that flash memory is certified for. The bonus is that ReRAM's read and write speeds are comparable, while flash takes a lot longer to write data than to read it.

HP and South Korea's Hynix have teamed up to mass-produce ReRAM chips that could be used in a variety of small devices, such as media players that can hold terabytes of songs, videos and e-books. They expect to see the first products on the market sometime in 2013.

ReRAM can also replace dynamic RAM in computers. Because it's nonvolatile, ReRAM won't lose its contents when the system is turned off or loses power, as DRAM does. In fact, Williams thinks it could lead to an era of instant-on computing. Even when today's devices are merely put to sleep instead of being fully shut down, it takes anywhere from a few seconds to a minute for them to access stored data upon awakening. But with ReRAM devices, you'd be able to pick up where you left off instantaneously.

R. Stanley Williams, HP Labs
R. Stanley Williams from HP Labs: "We can get to petabit chips within about 10 years."

What's more, Williams says, it's possible to stack memristor arrays on top of each other within a single chip. This could create 3-D memory elements that better use the space within a chip. Rather than just using the surface of the chip, these memory elements can be built deep down into the chip, creating much more memory in the same physical volume.

"There's no fundamental limit to the number of layers we can produce," adds Williams. "We can get to petabit chips within about 10 years." That's a million gigabits of storage space, or enough to hold more than a year's worth of high-definition video on a chip the size of a fingernail.

"The first application for memristors will likely be memory," says NIST's Seiler, "but there's much more to it than that. There's a lot of potential beyond memory."

Further out on the digital horizon, perhaps 20 years or so, the technology could rewrite basic computer design. In 2010, the HP researchers discovered that memristors can be used for logic computations in addition to storage. That means that both functions could theoretically occur in the same chip.

Says Williams, "A single memristor can replace a handful of other circuits, simplifying how computers are designed, made and operated." For instance, he says, one memristor could do the job of the six transistors that are currently used to create a single static RAM memory cell in a processor's cache.

Williams thinks it might even be possible to create an artificial neural synapse with memristor technology that could mimic the way the brain works. That's decades off in the future, however, if possible at all.

The memristor certainly has the power to rewrite the rules of electronics, says Supratik Guha, director of the physical sciences department at IBM. But, Guha notes, the technology still needs to prove itself. "There may be potential as a memory element," he says. "But like any other technology, you need to crawl before you walk and walk before you run."

In other words, memristor technology won't happen overnight. It will take a lot of evolution and time before memristors are as prevalent as DRAM or flash memory.

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