Atomic Force Microscopy vs Scanning Tunnelling Microscopy

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Atomic Force Microscopy (AFM)

Contact mode vs tapping/non-contact mode

Atomic force microscopy (AFM) sometimes referred to as scanning force microscopy (SFM) is a microscopy technique used to give a topographical image of a surface i.e. allows the analysis of the shape and features of the surface. It has relatively good resolution, though not as good as scanning tunnelling microscopy (STM).

There a two different types of imaging modes for AFM, contact mode and tapping/non-contact mode. In contact mode, the probe is brought into contact with the sample and scanned with the force kept constant (or height). This is a more destructive technique and only relevant for a relatively even surface. Alternatively, in tapping/non-contact mode the probe oscillates on/off the surface making it a less destructive technique.  

Scanning Tunnelling Microscopy (STM)

Image of a graphite surface at an atomic level obtained by an STM.

Scanning tunnelling microscopy (STM) is a similar technique, however it involves applying a voltage across the tip/sample to measure the tunnelling current, giving an electrons density of the surface. (read more about the science behind STM here).  STM can offer very high resolution, down to resolving individual atoms, however only surfaces that conduct electricity can be analysed using STM.

STM explained (Jubobroff)

Page Author; Thomas Squire

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