Engineering Memory of the Month

Happy 20th birthday to the atomic force microscope

In 1982, IBM scientists Gerd Binnig and Henrich Rohrer gave the world the scanning tunneling microscope (STM), a device so exquisitely precise that it could measure individual atoms on a conducting surface by running an extremely sharp, electrically sensitive tip over that surface. A small current, proportional to the distance of the tip from the surface below, would result. The scope measured the contours of the surface by raising and lowering the tip to keep the current constant. It was a great breakthrough in scientific measurement and imaging, but the surfaces it scanned had to be made of materials that were electrically conducting. The question remained, how to image insulating surfaces as finely.

On March 3, 1986, Binnig, IBM colleague Christoph Gerber, and Stanford electrical engineering and applied physics Professor Cal Quate announced the answer in a Physical Review Letters paper titled, "Atomic Force Microscope" (AFM). The image above is from that paper, which has been cited more than 4,000 times. Their first AFM actually used a diamond tip between the sample surface and an STM tip. The diamond tip would move up and down to keep a force between it and the undulating surface constant. The STM tip, in turn, measured the movement of the diamond tip. Quate and his colleagues showed the new scope was capable of 30 Angstrom resolution on insulating as well as conducting surfaces. For the STM, Binnig and Rohrer went on to win half the 1986 Nobel Prize in physics, while the AFM brought researchers expanded capabilities. Nowadays, modern AFMs are used more widely than STMs because while the STM requires a vacuum, the AFM can operate in open air.

Bring your Stanford Engineering memories out into the open air. Scan in your old photos from your school days and send them to David Orenstein, manager, Communications and P.R.