Working Principle of STM

When a sharp tip is positioned as a local probe above the surface and a voltage is applied, the tunneling of electrons results in a current, which exponentially decays with increasing distance between tip and surface. An increase in the distance of one Angstrom leads to a decrease in tunneling current by approximately one order of magnitude. It is this sensitivity, which ultimately causes the unique resolution of STM. 

The concept of a scanning tunneling microscope along with the first STM data were first published in the year 1982 by G. Binnig, H. Rohrer, C. Gerber and E. Weibel [52, 53]. Only five years later [54], its invention was awarded the Nobel prize in physics.  

How can the tunneling barrier width and the lateral position of the tip be controlled so accurately Tire tip is mounted on an actuator consisting of piezoelectric ceramics for reliable and exact positioning in all three dimensions (particular for the scanning). Only the nanometer positioning ability of piezo ceramics (see Tutorial 2 on Piezoelectric Tube Scanners and Translational Stages) made SPM techniques initially possible. 

4) STM on adsorbates and molecules is also performed on thin layers of insulators for application in catalysis and molecular electronics. 

Tutorial 2. Piezoelectric Tube Scanners and Translational Stages 

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Figure 9.5 Schematic illustration of working principle of STM-BI (a) and jump-to-contact-based nanostructuring and STM-BJ (b). The STM image in (b) is a ring of 48 Fe clusters created by jump-to-contact-based nanostructuring.

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