NANOTECHNOLOGY—TECHNOLOGY ON A MOLECULAR SCALE - Chemistry: Notable Research and Discoveries - page 52

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machine produces a contour of the surface with the preci-
sion of the size of the probe tip—a single atom!
When researchers position the tip even closer to the
surface, sometimes an atom will stick to the probe. If this
attractive force is strong enough, the atom will break free of
the surface and follow the probe. By picking up an atom and
then placing it down at another spot, STM allows scientists
to move material one atom at a time.
Semiconductors are made by “doping”—adding a small quantity of bo-
ron or phosphorus to silicon; controlling this process at the atomic level
might allow engineers to construct integrated circuits on a scale un-
imaginably small prior to the development of STM. The decrease in the
size of the components of an integrated circuit means that more of them
can be used, resulting in even more powerful computer processors.
nAnoMATErIAlS
Building materials atom-by-atom is not generally feasible yet, despite
the help of machines such as STMs. A square nanometer box—each
side having a length of 0.00000004 inches (0.0000001 cm), or, in other
words, one nanometer—contains about 500-1,000 atoms, many more
particles than researchers can efficiently move at the present stage of
science. But nanotechnology is not solely about moving atoms, design-
ing self-assembling molecules, and making tiny motors. Nanotechnol-
ogy also involves small-scale materials—“nanomaterials.”
Assembly is a field of nanotechnology that starts at the bottom, to
use Feynman's expression. The molecular construction proceeds by
putting together the pieces, either through a series of chemical reac-
tions performed by a chemist or through a process of self-assembly. A
different approach to nanotechnology begins with a material of interest.
The challenge is to fashion an extremely small yet functional object or