An introduction to scanning tunneling microscopy (STM) (Invited article)

Dr. Mostafa Enayat (Researcher at the Leibniz Institute for Solid State and Materials Research Dresden, Germany)

Scanning tunneling microscopy (STM) can be used to visualize the surface of conducting samples with atomic resolution. It has been widely used in research institutes and has revolutionized the realm of Nanoscience, hence honored the inventors “Binning and Rohrer” the Noble prize in Physics in 1986. This fascinating instrument operates based on quantum tunneling of electrons; if the distance between the tip and the sample is less than 1nm and voltage-bias is applied between them, electrons would tunnel between the tip and the sample thus generating a tunneling current. This current is extremely sensitive to the distance between the tip and the sample, which provides STM a vertical (depth) resolution with sub-Angstrom range, allowing to visualize atomic corrugations and charge ordering. By using a piezo-scanner tube it would be possible to scan through the surface by controlling the position of the tip. STM measurements are preferred to be carried out in UHV conditions to avoid dirt depositing on the surface. By measuring the tunneling current as a function of the applied bias at a fixed position of the tip, it would be possible to study the electronic excitations of many crystals and molecules with ultra-high spatial resolution.

Sketch

STM is used in numerous fields of research, including condensed matter physics where it has been used to study various Quantum-Materials like superconductors, topological insulators and graphene. By having a magnetic tip, it would be possible to do spin-polarized STM measurements where it would be possible to show magnetic structure on the surface with atomic resolution. STM is used to study single molecules on conductive substrates, where by taking spectroscopy it would be possible to study molecular electronics. It is also possible to move atoms to a precise position on the surface making it a tool for manipulating the quantum and Nano world.



Categories: Articles, Materials Science Methods

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