Rohrer, Heinrich (1933-2013), a Swiss physicist, worked on the scanning tunneling microscope (STM), the first microscope that was able to form images of individual atoms. Rohrer developed the STM with German physicist Gerd Binnig in 1981. In 1986, Rohrer and Binnig shared half of the Nobel Prize for physics.
Atoms are far too small to be seen with light, because even the shortest light-waves are more than 1,000 times longer than the diameter of an atom. Instead of light, the STM uses electrons, negatively charged subatomic particles that are found in all atoms. The STM contains a probe consisting of a very fine wire held close to the surface of a sample of material. When a high voltage is applied to the probe, electrons are pulled from the material into the probe, forming a tiny electric current. The probe is then scanned across the surface. If it meets a depression in the material, the distance between the probe and the surface increases and the electric current becomes weaker. If there is a bump in the surface, the distance decreases and the current gets stronger. To keep the current constant the probe is moved closer or farther away from the surface. Scanning the probe across the whole surface in this way provides a “relief map” of the atoms that compose the material.
Rohrer was born on June 6, 1933, in Buchs, Switzerland. He graduated in physics from the Swiss Federal Institute of Technology in Zurich and went on to take a Ph.D. there in 1960. From 1961 to 1963, he worked in the United States, doing research at Rutgers University in New Jersey. He then started work at the research laboratory of International Business Machines Corporation (IBM) in Zurich. Rohrer died on May 16, 2013.
