The device Dr. Rohrer created at an IBM laboratory in 1981 with Gerd Binnig was called the scanning tunneling microscope, and they shared half of the physics Nobel in 1986. (German scientist Ernst Ruska also received a physics prize that year for unrelated work on the electron microscope.)
The device became a pillar of nanotechnology, the manipulation of individual atoms and molecules to create useful devices. Nanotechnology deals with dimensions on the order of a few millionths of an inch. Objects that size cannot be seen with the most powerful optical microscope.
But quantum mechanics, the theory of matter on the atomic scale, helped point a way forward for Dr. Rohrer and his colleagues. In quantum theory, electrons have wavelengths, which are smaller than those of visible light. Thus, microscopes using electron beams rather than beams of light can see smaller objects.
The devices stemming from Dr. Rohrer’s work are even more powerful than the basic electron microscope. In part, they depend on a particularly startling feature of quantum reality: quantum tunneling.
In the quantum world, electrons can be in two places at once; they can show up on both sides of a seemingly impenetrable barrier. This phenomenon comes about through what is known as quantum tunneling, and the scanning tunneling microscope depends on it.
In the device, a probe with a tip as fine as a single atom moves over the surface of a material. Electrons tunnel through the minuscule gap between probe and surface. The current produced in this way varies with the distance between the probe and the surface.
High points on a surface, closer to the probe, create stronger current. For low points, the current is weaker. Charting the current yields a map of the surface.
Dr. Rohrer and his co-inventor produced an image suggesting a landscape of hills and valleys. But, they wrote, they recognized this image for what it was. They knew that the “pronounced and regularly arranged protrusions we saw” were actually individual atoms.
They had been told that such a precise finding was impossible.
“Rumors reached us that scientists would bet cases of champagne that our results were mere computer simulations!” they wrote. But their success soon became clear.
Heinrich Rohrer was born June 6, 1933, in Buchs, Switzerland, and moved with his family to Zurich as a teenager. Acknowledging that he was not one who had dreamed since childhood of physics, he nevertheless took it up at the Swiss Federal Institute of Technology in Zurich and went on to obtain bachelor’s and doctoral degrees there in 1955 and 1960, respectively.
After two years of postdoctoral work at Rutgers University in New Jersey, he returned to Switzerland in 1963 to work for IBM, where he conducted his prize-winning scientific investigations. Binnig worked for Dr. Rohrer at his laboratory in Zurich.
Survivors include his wife since 1961, Rose-Marie Egger, and two daughters.
At the outset of their Nobel lecture, Dr. Rohrer and Binnig said it was intended as a report on how they had worked, not as a recommendation for how others should work. In addition, they said, “it would certainly be gratifying if it encouraged a more relaxed attitude towards doing science.”