IBM makes molecular switch

The company has made two separate nanotech breakthroughs that could lead to switches made up of single molecules, and storage on single atoms

IBM researchers claim to have created the first molecular switch with the potential to be built into larger-scale systems and, on the same day, published results that could lead to magnetic storage at the level of single atoms. Both results are reported today, in Science magazine.

Scientists led by Peter Liljeroth at IBM's Zurich Research Laboratory have demonstrated a molecular switch based on a molecule called naphthalocyanine. There are two hydrogen atoms in the molecule's inner cavity, which have two possible positions. The atoms can be switched from one orientation to the other, producing a big change in the molecule's conductivity and allowing a microscopic logic-gate to be constructed, according to the abstract of the Science paper.

Although molecular switches have been built before, this one is different because the shape of the molecule remains constant. "In our switch, the shape doesn't change, only the hydrogen atoms in the centre move, Liljeroth told "This is very important if you want to make more complex devices using these switches."

The molecule — which Liljeroth found while testing a range of possible candidates — has another major benefit in building more complex devices. Liljeroth managed to show that when one molecule switches, it can influence the switching of adjacent molecules.

"When you are using a molecular switch, connecting it to other switches by normal copper wires is not practical," he said. "It makes more sense to connect the molecules directly, and build a network out of molecules." If a more complex logic device can be built out of a cluster of molecules, these could then be connected electrically to other clusters and real-world devices.

For now, the switch only works at low temperatures close to absolute zero. Liljeroth plans to investigate the strength of the coupling between systems and the possibilities of more complex systems before attempting to get closer to room temperature. "There are ideas on how it would be done, but this is very much an exploratory moment," said Liljeroth.

Meanwhile, scientists at IBM's Almaden laboratory in San Jose led by Andreas Heinrich have measured the ability of single iron atoms to hold a stable magnetic field (magnetic anisotropy), using a scanning tunnelling microscope (STM). Current hard disks use magnetic domains that include millions of atoms, so the ability to manipulate the magnetic field of a single atom could vastly increase the storage of magnetic media. More information can be found in the Science paper.

"We can literally take one atom, measure its magnetic anisotropy, put another atom next to it, see how that affects the [first atom's] magnetic anisotropy and from there learn how to develop a material with the ultra-high data-storage densities we are predicting," said Heinrich, quoted in EE Times.

As with the Zurich switch, Heinrich's work is at low temperatures, and needs more work before it can be built into larger systems, but the prospect of molecular storage has encouraged speculative fantasies by commentators about putting the entire contents of YouTube on an iPod.

IBM has considerable history in nanotechnology research. Twenty years ago, Gerd Binnig and Heinrich Rohrer of IBM's Zurich Lab were awarded the 1986 Nobel Prize in Physics for designing the scanning tunnelling microscope (STM), which first made it possible to see and manipulate individual atoms. Binnig and other IBM researchers also invented the atomic force microscope (AFM) in 1986.

In 1989 IBM's Don Eigler manipulated atoms on a surface, using the STM to position 35 xenon atoms so they spelt out "I-B-M", and in 1991 other IBM scientists built the first atomic switch. IBM scientists created a 10-atom abacus in 1996, and a molecular wheel in 1998.


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