scanning tunneling microscopy

Technique belonging to the group of scanning probe microscopy (SPM) used to directly observe individual atoms on surfaces. In STM a solid specimen in air, liquid or vacuum is scanned by a sharp tip located within a few Å from the surface. A quantum -mechanical tunneling current flows between atoms on the surface and those on the tip. The magnitude of the current depends upon the separation between the surface and tip atoms, so that it is possible to obtain surface topography with atomic resolution.