IBM's 1981 tunneling microscope saw single atoms by feeling current, not light

By the late 1970s, imaging had hit a wall. Optical microscopes stop at roughly the wavelength of light, and even electron microscopes — which had earned Ernst Ruska half of the 1986 Nobel — could not resolve individual atoms on a surface. At IBM's Zurich Research Laboratory, superconductivity physicists Gerd Binnig and Heinrich Rohrer were frustrated by exactly this: they wanted to study atomic surfaces, and no instrument existed to look at one.

The answer was quantum tunneling: electrons cross a vacuum gap between a sharp tip and a surface, and the current is extraordinarily sensitive to distance. Instead of a lens they built control: a one-atom-wide tungsten tip, piezoelectric scanners stepping it along by angstroms, feedback holding the current constant, and vibration isolation. The scanner's corrections became a topograph of the surface, atom by atom. Binnig filed the first patent disclosure in January 1979; after 27 months of development with Christoph Gerber, the instrument worked, imaging a gold crystal on 16 March 1981.

The resolution was unsurpassed — a 100-angstrom-square landscape rendered atom by atom — and the impact immediate, above all in semiconductors, where atomic-level knowledge of surfaces underpinned chip miniaturization. In 1990 IBM's Donald Eigler and Erhard Schweizer used an STM to position xenon atoms one at a time to spell "IBM," a demonstration that made nanotechnology credible. The Nobel Committee awarded Binnig and Rohrer half of the 1986 physics prize, citing their design of the scanning tunneling microscope for opening "entirely new fields ... for the study of the structure of matter."

No lens: feel atoms via tunneling current's sharp decay

The exponential distance-dependence of tunneling current converts sub-angstrom height differences into measurable current changes, so sensitivity comes from physics rather than expensive optics.

The tip does not need to see the whole surface at once; scanning plus feedback assembles the image point by point, which sidesteps the need for any atom-focusing lens.

IBM's research lab tolerated a two-year skunkworks on unproven physics, and the payoff leveraged the company's core semiconductor business where atomic surface knowledge was directly valuable.

They built on Russell Young's earlier topografiner work at the National Bureau of Standards but attacked his weak points — vibration, drift, and tip control — rather than the concept.

When your tool cannot reach the scale you need, find the proxy that can. Tunneling was textbook physics; reading its exponential sensitivity as resolution turned a curiosity into an instrument.

The STM opened nanotechnology as a discipline: it gave semiconductor, molecular biology, and materials labs a direct view of atomic surfaces, and later enabled manipulating individual atoms. Its descendants — the atomic force microscope family — now probe surfaces that do not conduct. IBM opened the Binnig and Rohrer Nanotechnology Center in Rüschlikon in 2011, and the instrument's first images, taken on a March night in 1981, are a founding artifact of the field.