7 The 100 Most Influential Inventors of All Time 7brought to within five or ten atoms’ distance of the surface
of a conducting or semiconducting material. (An atom is
equal to about one angstrom, or one ten-billionth of a
metre.) When the electric potential of the tip is made to
differ by a few volts from that of the surface, quantum
mechanical effects cause a measurable electric current to
cross the gap. The strength of this current is extremely
sensitive to the distance between the probe and the surface,
and as the probe’s tip scans the surface, it can be kept a
fixed distance away by raising and lowering it so as to
hold the current constant. A record of the elevation of
the probe is a topographical map of the surface under
study, on which the contour intervals are so small that the
individual atoms making up the surface are clearly
recognizable.
Gerd Binnig
The German-born Gerd Binnig graduated from Johann
Wolfgang Goethe University in Frankfurt in 1973 and
received a doctorate from the University of Frankfurt in
- He then joined the IBM Zürich Research Laboratory,
where he and Rohrer designed and built the first STM. In
1985–86 Binnig joined a physics research group at IBM’s
Almaden Research Center in San Jose, Calif., and in 1987–
95 he directed an IBM research group at the University of
Munich. He then returned to Zürich.
About the time Binnig shared the Nobel Prize with
Rohrer for the invention of the STM, he developed the
concept of atomic force microscopy. An atomic force
microscope profiles a sample by dragging a stylus only a
few atoms wide across the surface of the sample and
measuring the force between the stylus and the surface.
The resulting signal can be translated into a description of