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Scanning tunneling microscopy

Scanning tunneling microscopy

Scanning tunneling microscopy is a technique able to explore the electronic states at surfaces, reaching in this way to some topographic information. The Nobel prize was awarded to Gerd Karl Binnig and Heinrich Rohrer in 1986 for the first realisation of this instrument, which was shared with Ernst Ruska for the electronic microscope. The technique consists of approaching a tip to the sample. A voltage bias is settled between tip and surface. If the tip is close enough to the surface but there is no contact, electrons can flow between tip and sample due to the electrons that travel through the potential barrier by quantum tunneling. Topographic images can be obtained by scanning the surface with the tip. It is possible to constrain the tip-sample current to be constant during this process. In this way, the vertical tip displacement reports on the topography of the surface.

Scanning tunneling microscopy principle. A tip scans the sample and a voltage is settled between sample and tip. If the distance between them is small enough without contact, electrons can flow through the potential barrier between sample and tip by quantum tunneling. By recording the tip height variation when scanning the surface in a rectangular region, the STM image is obtained.

Film of the scanning tunneling microscopy principle. Courtoisy of Julien Bobroff.