Exploring the nanoworld with atomic force microscopy

The atomic force microscopy (AFM) has gradually evolved over the years into an instrument whose resolution is now fine enough to image sub atomic features on the scale of picometers. In an AFM, the cumulative force, which is a mixture of short and long-range interactions, is much less tractable as a feedback signal. The key task in achieving true atomic resolution is to single out the chemical-bonding forces of surface atoms on the front atom of the tip from the various other forces at play and exploit its signal for distance feedback. The AFM may be configured so that its cantilever swings only close enough to capture the initial stages of bonding or may make and break those bonds during each oscillation cycle. The force between an AFM tip and the sample also depends on their respective chemical identities and the distance between them, and also on the tip atom's angular orientation with respect to atoms that support it and with respect to atoms on the surface.