A pattern of tiny magnets can store data at unprecedented densities (Image: Science)

For more than 40 years, computer processors have increased in power and shrunk in size at a tremendous rate. But engineers are approaching the point where there is not much more to be gained from tweaking the traditional ways of making those components (see our feature What happens when silicon can shrink no more?).

However, advanced new forms of transistors and memory unveiled this week could develop into products that keep that growth from tailing off.

Two US groups have announced transistors almost 1000 times smaller than those in use today, and a version of flash memory that could store all the books in the US Library of Congress in a square 4 inches (10 cm) across.


Domino effect

Thomas Russell at the University of Massachusetts and his international team have become the first to realise a long-mooted idea – that flash memory could be made from patterns of nanoscale magnets.

The group has worked out how to make the memory build itself, in a cascading domino-like effect.

They found weakening a specific plane in a sapphire or silicon wafer brings a subtle instability to the highly ordered crystal. Heating the crystal to around 1400 °C then emphasises the instability and the atoms rearrange, producing a saw-tooth pattern of depressions across the wafer’s surface.

That pattern is then used to shepherd polymers into a regular repeating nanoscale pattern and make a mask to create an array of tiny nickel magnets. Each of these can store digital bits (1 or 0) in their magnetic north-south orientation.

Dense data

Using 3-nanometre magnets, an array could store 10 terabits (roughly 270 standard DVDs) per square inch, says Russell, who is now working to perfect magnets small enough to cram 100 terabits into a square inch.

“Currently, industry is working at half a terabit [per square inch],” he says. “They wanted to be at 10 terabits in a few years’ time – we have leapfrogged that target.”

Sebastien Lecommandoux who researches self-assembling nanotechnologies at the University of Bordeaux, France, is impressed. “The work described can, I believe, bring a real breakthrough in high-capacity storage devices.”

Tiny transistors

This week also saw the announcement of an advance that could shrink the transistors used to make computer processors by 1000 times.

The smallest features in current silicon transistors are 45 nanometres in size, but the latest made by Jeremy Levy at the University of Pittsburgh and colleagues have features just 2 nanometers in size, allowing many more transistors to be crammed into the same area.

Rather than building them from silicon, the team used two different forms of the common mineral perovskite. When two of the insulating crystals of the right thickness are held together, the place where they meet can conduct electricity. But if one of the pieces is too thin, then current will not flow.

Working with wafers that were just too thin to conduct, Levy’s team found that they could “draw” conducting patches onto the crystal using a microscopic needle. A positive voltage from the needle rearranges the crystal’s atoms to create lines 2 nm across that conduct like electrical wire.

Write and erase

The process has been used to make transistors roughly 1000 times smaller in area than those fashioned from silicon. The “wires” can also be easily erased and recreated up to 100 times.

Being able to erase parts of a design and write over them again also offers more exotic possibilities, says Levy. It could be possible to use the phenomenon to could create hardware that rewires itself as it handles data, he says.

“It could blur or dissolve the distinction between software and hardware, for example by integrating memory and logic,” he says.

Jean-Marc Triscone at the University of Geneva has shown that perovskite crystals can also behave as superconductors. “The achievements of Levy and co-workers coupled to [our] superconductivity [work] may allow small electronic circuits to be realised, which would open many interesting possibilities,” he says.

Journal references: Russell’s paper: Science (DOI: 10.1126/science.1168108) Levy’s paper: Science (DOI: 10.1126/science.1168294)