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Scanning Tunnel Microscopy (STM)

Schematic layout of a scanning tunnelling microscope

(Kopie 2)

The Scanning Tunnelling Microscope (STM) relies on the quantum-mechanical tunnelling effect. Upon the approach of a conductive, nanoscopic tip towards a likewise conductive sample surface, an electron exchange can take place under a nanometre at certain distances. The electrons can overcome the energy barrier and, because their probability density on the other side of this barrier is not zero, they can have unoccupied states. If voltage is applied between the sample and the tip, this produces a measurable tunnel current, the strength of which is very much location-dependent. If the value of this current is applied based on the tip position, this produces an image that contains combined information regarding electronic states and topography. Because these often correspond in the present scales, a representation of the sample surface can be produced with an atomic resolution.

 

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