Scanning Tunneling Microscope

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

In 1978 Gerd Binnig and Heinrich Rohrer, a young theorist and an established experimentalist at IBM Zurich Research Laboratory, set out to study extremely thin insulating films by exploiting quantum tunneling, the small but nonzero probability that an electron can cross a gap it classically has no energy to cross. To do that cleanly they first needed to solve a harder problem, how to hold a metal tip within a fraction of a nanometer of a sample surface, stable enough that the tunneling current between them would not be swamped by vibration. Their solution, delivered in 1981, combined piezoelectric positioners that could move the tip in steps smaller than an atom's diameter with a feedback loop that adjusted the tip's height to keep the tunneling current constant as it scanned. The trace of those adjustments turned out to be a direct map of the surface's atomic structure, the first time anyone had imaged individual atoms sitting on a surface rather than inferring their positions indirectly. Binnig and Rohrer shared half of the 1986 Nobel Prize in Physics for the invention, the other half going to Ernst Ruska, whose electron microscope, built half a century earlier, the scanning tunneling microscope now sat beside as a second way of seeing what no eye, and no ordinary lens, ever could.

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

The scanning tunneling microscope did more than let physicists see atoms. It let them move them. In 1990, researchers at IBM Almaden lab used an STM tip to drag 35 individual xenon atoms across a nickel surface, one at a time, and arrange them to spell out the company's initials, the first time anyone had deliberately built a structure atom by atom. The demonstration was part publicity stunt and part serious proof of principle, if a tip could image a surface at atomic resolution, the same tip, under slightly different conditions, could push, pull or pick up single atoms and place them somewhere else. That capability became one of the founding tools of nanotechnology, the deliberate engineering of matter at the scale of individual atoms and molecules, and the STM's descendants, including the atomic force microscope developed a few years after Binnig and Rohrer's original instrument, remain standard equipment anywhere surfaces need to be understood, or built, one atom at a time.