The Sharp End of Nanotechnology

We have known about the atomic nature of the structure of matter for over a century, however this microscopic world was always considered abstract and invisible, hidden from our direct view by the limitations on how closely we can look at any material that forms everyday reality. Over the past two decades, this divide has been dramatically removed with the development of a new class of microscopes that allow us to probe and even manipulate the surfaces of materials with unprecedented precision.

The invention of the Scanning Tunnelling Microscope (STM) in 1982 by the IBM researchers Gerd Binnig and Gerhard Rohrer (for which they were awarded the Nobel prize four years later), allowed us for the first time to directly observe the structure of matter on the atomic scale. In the STM, a sharp metallic tip (terminated with a single metal atom) is scanned back and forth across the material to be observed, and an effect know as 'quantum tunnelling' results in a very small electrical current flowing between the tip and the surface, which can be measured very precisely and is used to create the images. The amount of current that flows is very sensitive to the exact distance between the tip atom and the atoms in the surface, and in this way the microscope can resolve an atomic structure.

The resolution of the STM is much finer than other forms of microscopy: an optical microscope can resolve details down to approximately 0.5 micrometers (500 nanometers), a scanning electron microscope can resolve a few nanometres, whereas the the STM can resolve features down to almost 0.1 nm.