Supposedly stupendous memory technologies have come and gone before without ever ruffling the commercial market. Holographic memory as a mass-market technology has been "just around the corner" for at least 25 years. More recently, schemes based on molecules or even bacterial proteins have excited researchers before turning out to have essentially insurmountable manufacturing, longevity, or other problems.

What makes probe memory different is that it is based on proven technologies. Probe memory is an offshoot of the scanning probe microscope, a form of which was invented in 1981 by Binnig (hence his Nobel prize) and Heinrich Rohrer, a Swiss physicist who retired in 1997 after 34 years at ZRL. These nonoptical microscopes, which include the scanning tunneling and atomic force microscopes, scan the surface being examined with the tip of a long, thin wisp of metal or silicon called a cantilever. The cantilever's probe tip is just atoms wide, so it maps surfaces with atomic-scale resolution.

PHOTOS: PAT MAZZERA; CHRISTIAN DIETRICH

The pioneers of probe: Nanochip founder and CTO Tom Rust [left] and CEO Gordon Knight are vying for the nanotech-storage prize. Nobel laureate Gerd Binnig [far right], inventor of the scanning probe and atomic force microscopes, is the driving force behind IBM's Millipede project.

Basically, a probe memory uses arrays of dozens or hundreds of these same tips to write, read, and erase nanoscale bits in neat columns on a piece of storage medium made of specially engineered plastic or an exotic alloy. Depending on the probe-drive design, either the storage medium or the probe-tip array is mounted on a moving platform, which scans the stationary component to align the tips with either bits to be read or locations where bits are to be written. To write, read, or erase data, the tips are heated and then pressed onto the medium. Because the tips are so fine, the bits occupy spaces on the medium just 10 nanometers wide, or roughly the width of 100 hydrogen atoms.

Like a hard disk drive or an optical disc drive, a probe-drive system accesses data at random locations by reading current through the tips as they pass over the bits to determine whether they are 1s or 0s. Control circuitry aligns the mechanical components with nanometer precision, and error-correction codes ensure the integrity of the data being written and read. The basic concept has been proved over and over by both IBM and Nanochip. The game now is making the memory devices cheaply by the millions and fabricating probe tips that, despite their extreme delicacy, can withstand the wear of tens of thousands of read/write cycles.

The story of probe storage begins with Binnig's co-invention of the scanning tunneling microscope (STM) 24 years ago. It let researchers see, for the first time, surface features down to the atomic scale. With a voltage applied to it, an STM's ultrasharp tip, which is very close to but not touching a sample of conductive material, attracts electrons from the material's surface atoms, resulting in a weak current. Since the amount of current depends on the distance between the tip and the surface, measuring the current as the tip scans the sample provides the data necessary to plot a three-dimensional picture of the sample's surface.

It was Nobel-quality work, but Binnig was already looking for something better: he wanted to image insulators as well as conductors. He was drowsing on his couch while on sabbatical in 1985 when he literally dreamed up the idea of the atomic force microscope, or AFM, which would eventually become the basis for probe-storage technology. In the process of creating these two nonoptical instruments to image materials on the atomic scale, he had stumbled on a means to manipulate, as well as characterize, matter at the nanoscale. In effect, he had opened a window on what the physicist Richard P. Feynman famously termed the "bottom," in his 1959 talk at the annual meeting of the American Physical Society about "the problem of manipulating and controlling things on a small scale."

Throughout the 1980s, atomic manipulation with STM probes fascinated researchers. Several labs, including ones at AT&T, Stanford University, Hitachi, and the U.S. National Institute of Standards and Technology, used STM probes to build crude features on surfaces atom by atom. But it wasn't until 1990, when Nature published the now famous picture of the letters I-B-M spelled out in 35 xenon atoms, that it really hit home with people outside the insular STM research community: you could use probes to move individual atoms around in a highly controlled manner [see photo, "Small Blue"].

Among the people most impressed by "IBM" writ small was Nanochip founder and chief technology officer Tom Rust. If you could use probe tips to create orderly patterns on surfaces, he reasoned, it followed that you could use those same STM probes to write and read data. "I saw what IBM had done with a scanning tunneling microscope and spelling out 'I-B-M,'" he says, "and that inspired me to use probes to build a disk drive."

It was 1991, and Rust, an engineer who had spent most of his career working on hardware and software for displays, had just devoured K. Eric Drexler's nanotech manifesto Engines of Creation (Anchor Press/Doubleday, 1986). He was looking for a way to engineer Drexler's ideas into products when IBM, his future rival, provided the answer. Though he had no experience with nanotechnology, he plunged into it with the fervor of a true believer.

Rust's divergent career had begun in 1975, when, as an undergraduate computer science major at the University of Illinois at Urbana-Champaign, he took on a consulting gig for Magnavox Co. to build one of the first graphic cathode-ray-tube displays. He soon dropped out of college to create arcade video games and eventually went on to run a series of small businesses that produced 3-D solid modeling and animation hardware and software. This phase of his career culminated in a commission from the government of Singapore in 1990 to build a $2 million laser-dappled musical water fountain that now gushes on Sentosa Island, off Singapore's coast.

Then, infected by Drexler's visions of nanomechanical assemblers that could fabricate any kind of material or machine from the atoms up, he "caught the nanotechnology bug" and holed up for several weeks in the library stacks at the University of California, Berkeley, and Stanford University doing what he had done his whole life—teaching himself something new. He quickly concluded that he would have to use some sort of MEMS-based device as a platform for his STM probe, so he delved into technical journals to learn MEMS design and manufacturing.

After hearing that Lawrence Livermore National Laboratory, in California, had an STM, Rust contacted the lab and learned of a U.S. Department of Energy program that provided $5000 grants to small businesses so they could access lab facilities and services. Rust applied, and soon he found himself at Livermore developing a write-once medium on which an STM could make 30-nm diameter "donuts," his first nanobits. For that he and Joanne Culver, his research partner and wife, were awarded U.S. Patent No. 5453970, but further investigation and extensive reading quickly led him to shift from his original STM concept to another technology invented by Binnig at IBM, the atomic force microscope.

Both map the topography of the surface of a material using a sharp-tipped cantilever, but in contrast to the STM, the AFM maps the surface of a material with laser light. As the probe scans the sample surface, the electron clouds orbiting the atoms at the tip bump the ones orbiting the atoms on the sample's surface, ever so slightly deflecting the cantilever. A photodetector records the laser light reflected off the cantilever, providing the data necessary to determine the amount of deflection, and to create a 3-D image of the surface topology.

While intrigued with the idea of using an AFM tip in direct contact with a surface to read and write bits, Rust knew that the speed of the tip skimming over a spinning disk would quickly grind the tip down. So he designed a MEMS device that would hold the tip and help it nimbly skip over the rotating platter, touching down only where it needed to write a bit, until it ran out of travel. Then the MEMS platform would hop backward over the medium, not unlike the automated stylus arm on a turntable, which at the end of a record picks up and moves back to the starting position.

"One day I was looking at the complexity of this and thought, well, this is crazy!" says Rust with a chuckle. Instead of skip-hopping heads over a spinning disk, he figured he could have the MEMS platform move up and down and side to side over a stationary storage material, radically cutting down on component complexity and power consumption. The Nanochip was born.

Rust built the first MEMS devices in 1994 with a 0.8-micrometer process traditionally used for making chips. He designed and built four platforms per die, with eight cantilevers on each, along with some electronic controls. It was, he admits, a dismal failure that taught him a lot about MEMS and chip design and fabrication, including the fact that the Nanochip (or IBM's Millipede for that matter) doesn't need to be made by the world's most advanced 90-nm chip fabrication process. An old 1-mm fab is perfectly capable of making MEMS scanners and AFM tip arrays, a major reason that researchers are confident they'll be able to fabricate probe drives cheaply.

For the next two years, Rust shuttled across San Francisco Bay between his house in Oakland and the Stanford campus, where he paid to use MEMS fabrication equipment to prototype his designs and tweak the fabrication process. By 1996, he had made enough progress to impress his deep-pocketed friend Jerry Fiddler, founder of Wind River Systems Inc., a software company in Alameda, Calif. With Fiddler's backing, Rust phased out his computer graphics business and incorporated his new endeavor as Nanochip.