When a voltage is put between the tip of an STM and the sample, a small amount of current tunnels across the gap between tip and sample. The amount of current that tunnels is proportional to the distance between the tip and sample. That is to say: the closer the tip is to the sample, the more current flows across. As the tip scans over the sample, the distance between tip and sample changes and the amount of current changes. By measuring the current you can tell how close the sample is to the tip. By scanning over the entire sample, you can actually generate a picture of the surface, accurate to less than 1 nanometer. Using this technique, amazingly small things can be seen. For example it is possible to resolve the individual atoms in a carbon nanotube and to actually SEE the carbon honeycomb structure. You can also see the individual atoms of an O2 molecule absorbed onto a surface at low temperatures. Click Here to see some nice STM images Courtesy of Dr. Robert Wolkow, University of Alberta Continue on to the final thoughts.
© 2006 M. Busuttil, I. Kandikov, M. Lubrick, J. Mutus, J. Nantais