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Heinrich Rohrer
(1933)
Swiss physicist who, with Gerd Binnig, received half of the 1986 Nobel
Prize for Physics for their joint invention of the scanning tunneling
microscope. (Ernst Ruska received the other half of the prize.)
Rohrer was educated at the Swiss Federal Institute of Technology in
Zurich and received his Ph.D. there in 1960. In 1963 he joined the IBM
Research Laboratory in Zurich, where he remained. Binnig also joined
the laboratory, and it was there that the two men designed and built
the first scanning tunneling microscope. This instrument is equipped
with a tiny tungsten probe whose tip, only about one or two atoms wide,
is brought 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.
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