Chemical identification of individual surface atoms by atomic force microscopy

Name that atom Dynamic force microscopy, which works by detecting the interaction force between the oscillating tip of an atomic force microscope (AFM) and a surface, has been refined to the extent that it can achieve true atomic resolution of insulator, semiconductor and metal surfaces. In a landmark publication in this issue this technique has been used to perform the chemical identification of individual atoms in a multi-element system. The method involves precise quantification of short-range chemical forces between the probed atoms and the AFM tip, and provides a robust and general recognition tool suitable for both cryogenic and room temperature environments. The cover shows a topographic image of a surface alloy made up of silicon (red), tin (blue), and lead atoms (green) in equal proportions on a silicon (111) substrate. This atomic identification method is relevant to a wide range of research areas such as catalysis, materials science and semiconductor technology.