Funding

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To begin with, small amounts of dye molecules
are placed in powder form onto a
vaporizer (top photo). The molecules are then
evaporated onto an insulator surface and
later stimulated by a scanning tunneling
microscope (STM). Liquid nitrogen and liquid
helium are used to keep the STM at extreme
low temperature. Our photo shows Professor
Dr. Jascha Repp filling the nitrogen tank.
from the sides of this quadrant to the top and bottom, or vice versa, the
geometry of the molecule remaining constant.
“This molecule acts as a switch since the electrical current changes upon flipping
of hydrogen atoms”, he elucidates. However, just one switch of this type
is clearly not enough for electronic applications. If, though, we can succeed in
linking several up into larger switching arrays it will be possible to transport
information via the molecules. And this is what he and his colleagues from
the IBM research laboratory in Zürich actually did achieve when they succeeded
in joining up three such molecules – “just a small step towards building
more complex switches with single molecules”, Jascha Repp points out.
However, an accomplishment that led to a publication in the renowned journal
“Science” (31 August 2007, Vol. 317. no 5842, pp.1203-1206).
Of course, it is not possible to build this type of switch on the lab bench. The
laboratory he and his colleagues work in resembles something between a
science-fiction film set and a submarine. Vast surfaces of polished stainless
steel meet the eye in the basement rooms of the Institute for Experimental
and Applied Physics in Regensburg. Heavy bolts and flanges hold the small
steel chamber together, there are just narrow windows through which the
researchers can look into the inside. “All our experiments have to be carried
out inside this chamber”, Jascha Repp explains, “and we cannot enter it ourselves,
or even use our hands”. Using small metal grips controlled from the
outside, he evaporates the dye molecules onto the insulator, where then in
the center of the cold steel chamber they are stimulated and activated by
means of a fine needle. At its center, the chamber houses a scanning tunneling
microscope. Through this instrument, no bigger than a man’s fist, the
Regensburg scientist can view the individual atoms which make up his molecules.
The space in which Jascha Repp moves things around with his grips is
completely empty: Quite literally so – for he is working in an ultrahigh vacuum.
Moreover, it is extremely cold. His very special switches will only function at
nearly absolute zero, i.e. around minus 270 degrees Celsius. The needle of the
scanning tunneling microscope moves infinitely slowly over the research
specimen, scanning the surface atom by atom.
This sort of work calls for immense patience. Jascha Repp, though, is a patient
person. Full of patience. Working with the grips in an ultrahigh vacuum
chamber is not really so bad, he says; it takes him about half a day to prepare
a specimen. And even when his equipment – which he built himself by the
way – sometimes suffers a breakdown, he remains perfectly calm. He may
well do so, for half a week will have to pass by before he is even able to examine
a defective soldering joint, for instance. For it takes much more then just a
few minutes to fill the vacuum in the chamber with air and warm it up to
room temperature. “A much bigger problem than that, though, is that we
then have to put the whole steel chamber inside a huge sort of heated oven
to get rid of the condensed water on the chamber walls.” There is pleasure