Scanning tunneling microscope

Not to be confused with scanning electron microscope (SEM).
Image of reconstruction on a clean (100) surface of gold

A scanning tunneling microscope (STM) is a type of scanning probe microscope used for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer, then at IBM Zürich, the Nobel Prize in Physics in 1986.[1][2][3] STM senses the surface by using an extremely sharp conducting tip that can distinguish features smaller than 0.1 nm with a 0.01 nm (10 pm) depth resolution.[4] This means that individual atoms can routinely be imaged and manipulated. Most scanning tunneling microscopes are built for use in ultra-high vacuum at temperatures approaching absolute zero, but variants exist for studies in air, water and other environments, and for temperatures over 1000 °C.[5][6]

Scanning tunneling microscope operating principle

STM is based on the concept of quantum tunneling. When the tip is brought very near to the surface to be examined, a bias voltage applied between the two allows electrons to tunnel through the vacuum separating them. The resulting tunneling current is a function of the tip position, applied voltage, and the local density of states (LDOS) of the sample. Information is acquired by monitoring the current as the tip scans across the surface, and is usually displayed in image form.[5]

A refinement of the technique known as scanning tunneling spectroscopy consists of keeping the tip in a constant position above the surface, varying the bias voltage and recording the resultant change in current. Using this technique, the local density of the electronic states can be reconstructed.[7] This is sometimes performed in high magnetic fields and in presence of impurities to infer the properties and interactions of electrons in the studied material.

Scanning tunneling microscopy can be a challenging technique, as it requires extremely clean and stable surfaces, sharp tips, excellent vibration isolation, and sophisticated electronics. Nonetheless, many hobbyists build their own microscopes.[8]

  1. ^ Binnig G, Rohrer H (1986). "Scanning tunneling microscopy". IBM Journal of Research and Development. 30 (4): 355–369. doi:10.1016/0039-6028(83)90716-1.
  2. ^ Binnig G, Rohrer H (1987-07-01). "Scanning tunneling microscopy—from birth to adolescence". Reviews of Modern Physics. 59 (3): 615–625. Bibcode:1987RvMP...59..615B. doi:10.1103/RevModPhys.59.615.
  3. ^ "Press release for the 1986 Nobel Prize in physics".
  4. ^ Bai C (2000). Scanning tunneling microscopy and its applications. New York: Springer Verlag. ISBN 978-3-540-65715-6.
  5. ^ a b Chen CJ (1993). Introduction to Scanning Tunneling Microscopy (PDF). Oxford University Press. ISBN 978-0-19-507150-4. Archived from the original (PDF) on 2022-12-18.
  6. ^ SPECS. "STM 150 Aarhus – High Stability Temperature Control" (PDF). specs.de. Archived from the original (PDF) on 2017-02-23. Retrieved 23 February 2017.
  7. ^ Voigtländer, Bert (2015), Voigtländer, Bert (ed.), "Scanning Tunneling Spectroscopy (STS)", Scanning Probe Microscopy: Atomic Force Microscopy and Scanning Tunneling Microscopy, NanoScience and Technology, Berlin, Heidelberg: Springer, pp. 309–334, doi:10.1007/978-3-662-45240-0_21, ISBN 978-3-662-45240-0, retrieved 2020-10-15
  8. ^ "STM References – Annotated Links for Scanning Tunneling Microscope Amateurs". Retrieved July 13, 2012.