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Tech Page: Think Small

November 1, 2007
picture of microscope tip hovering over molecules

FIG. 1: A scanning tunneling microscope probes a pair of naphthalocyanine molecules with two hydrogen atoms at their centers. When the atoms change position, the entire molecule is electrically switched on and off, creating a rudimentary logic gate. Credit: Courtesy IBM

Every electronic musician knows that digital technology decreases in size as it increases in power. Intel cofounder Gordon Moore quantified this trend in his now-famous prediction that the number of transistors in a square inch of integrated-circuit material doubles every couple of years. Now known as Moore's law, his prediction has held true since it was first stated in 1965.

But how long will it continue to hold true? If IBM scientists have their way, it could be a while. Teams at the IBM Almaden Research Center ( in San Jose, California, and the IBM Zurich Research Lab ( in Switzerland are working on separate projects that could point the way to atomic memory elements and molecular logic gates.

The Almaden team is exploring a property of atoms called magnetic anisotropy, which refers to the fact that under certain conditions, an atom's spatial orientation can be controlled and measured. Ultimately, putting an atom in one orientation could represent a 0, while putting it in a different orientation could represent a 1.

Up to now, no one has been able to measure a single atom's magnetic anisotropy, but with the help of a scanning tunneling microscope, which was invented by IBM scientists 20 years ago, the Almaden team has successfully positioned and measured the anisotropy of individual iron atoms on a specially prepared copper surface.

“One of the major challenges for the IT industry today is shrinking the bit size used for data storage to the smallest possible features, while increasing the capacity,” says Gian-Luca Bona, manager of science and technology at the Almaden Research Center. “We are working at the ultimate edge of what is possible, and we are now one step closer to figuring out how to store data at the atomic level.”

Meanwhile, the Zurich team is working on another thorny problem: creating molecular switches that can function as transistors. Molecular switches have been demonstrated before, but they tended to change shape during the transition from one state to the other, making them unsuitable as logic gates or memory elements.

Using two hydrogen atoms within an organic molecule called naphthalocyanine, the team has created a stable switch that retains its shape as it turns on and off (see Fig. 1). Interestingly, this discovery was made by accident; the original intent of the research was to study the molecule's vibrational characteristics. But the team discovered that naphthalocyanine can behave as a switch without changing its shape.

“One of the beauties of doing exploratory science is that by researching one area, you sometimes stumble upon other areas of major significance,” notes Gerhard Meyer, senior researcher in the nanoscale science group at the IBM Zurich lab. “Although the discovery of this BREAKthrough was accidental, it may prove to be significant for building the computers of the future.”

It will be many years before any commercial products emerge from these developments, but they point the way toward atomic and molecular computing and storage. Imagine packing 150 trillion bits of data into a square inch of space, 1,000 times the density of current technology. That's the equivalent of 30,000 full-length movies or the entire contents of YouTube in a device the size of an iPod. Or how about a nanoprocessor the size of a dust mote?

Such advances in computer technology could enable heretofore unimaginable musical tools, like virtually unlimited audio storage in memory chips the size of postage stamps and real-time DSP operating on a nearly infinite number of super-high-resolution tracks. I don't know about you, but I'd sure like to see something like that in my home studio.

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