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scanning tunnelling microscopy

(Science: procedure) A form of ultra high resolution microscopy of a surface in which a very small current is passed through a surface and is detected by a microprobe of atomic dimnensions at its tip that scans the surface by use of a piezodrive. In the simplest form the current transferred to the probe is recorded as an indication of the contours of molecules on the surface above the local plane. In more complex forms feedback is used to hold the probe at a constant difference and the signal in the feedback loop indicates the contours of the molecule. Capable of resolving single atoms and known to work for nonconducting molecules as well as conducting ones.