Scanning Tunneling Microscopy


Gold atoms on an insulating NaCl film on copper.


The change in charge state is revealed by the dark trough around the gold atom.

False-colour three-dimensional image.

The gold atom on the left-hand side has been intentionally negatively charged using the STM tip.

http://physicsweb.org/article/news/8/7/13#Repp1
J. Repp, G. Meyer, F. E. Olsson, and M. Persson, Science, 305. 493-495 (2004).