"As a research scientist you are driven by the desire to find things out with ail your might."
Gerd Karl Binnig
As recently as thirty years ago the idea of being able to "see" bumps and grooves on substances at an atomic scale seemed unachievable. Then, in 1981, Gerd Karl Binnig (b. 1947) and Heinrich Rohrer (b. 1933) created a microscope capable of doing just that.
Their scanning tunneling microscope (STM) bears little resemblance to a conventional microscope. Operating at a low temperature and in a vacuum, it consists of a very sharp needle (its end is the width of a single atom), which can be brought very close to the sample being examined. It is a tool that "senses" rather than "sees" because it deals with sizes that are smaller than the wavelength of light.
The STM exploits a phenomenon of quantum mechanics known as electron tunneling where electrons can jump (or "tunnel through") small gaps between atoms. In electricity-conducting materials, such as metals, electrons flow from one atom to another. If the STM needle tip is projected close enough, this electron flow can be detected as the electrons tunnel from the metal surface to the tip. The needle tip can then follow the contours of the surface to reveal its shape. The result is a picture of the molecule in the nanometer range (one nanometer is a billionth of a meter, or the width of three atoms).
The STM's needle also allows scientists to move individual atoms by applying an electric field to the sample The tip attracts the electrons making up the atoms of the sample and pulls them around. In 1990 this was famously used to make the smallest branding In the world when the IBM logo was created out of thirty-five xenon atoms on a nickel plate.
