Scanning tunneling microscope

The scanning tunneling microscope (not to be confused with scanning electron microscopes), or STM, was invented in 1981 by Gerd Binnig and Heinrich Rohrer of IBM's Zurich Lab in Zurich, Switzerland. The invention garnered the two a Nobel prize for physics in 1986. The STM allows scientists to see and position individual atoms with higher resolution than its related cousin, the atomic force microscope (AFM). Both the STM and the AFM fall under the class of scanning probe microscopy instruments.

Use of the STM

STM is one of the most important tools for surface physics and surface chemistry, where it shows the structure of the topmost layer of atoms or molecules, e.g., defects and surface domain formation, morphology of thin films grown by various deposition techniques or modifications of surfaces by chemical processes.

Related Topics:
Surface chemistry - Deposition techniques

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For high-resolution of metals and semiconductors, the STM is usually operated in ultrahigh vacuum to avoid contamination or oxidation of the surface. Samples that are less sensitive to the atmosphere, such as graphite, self-assembled monolayers and Langmuir-Blodgett films can be imaged with high resolution under air. The tip of an STM can be also immersed into an electrochemical cell to study processes in electrochemistry (electrochemical STM).

Related Topics:
Ultrahigh vacuum - Graphite - Self-assembled monolayers - Langmuir-Blodgett film - Electrochemical cell - Electrochemical STM

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Far from simply a fancy microscope, the STM offers much in the way of surface science studies. Conduction mechanisms can be studied by analyzing a substrate via scanning tunneling spectroscopy, or STS, for which the feedback loop is momentarily interrupted during a scan to obtain dI/dV (point conductance) measurements. Furthermore, the STM can be used to study charge transport mechanisms in molecules or other extremely small structures such as carbon nanotubes.

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STM is also a tool for modification of surfaces through various methods such as indenting the tip or modification of the substrate by the electrons emitted from the tip. At low temperatures (typically, 4K) it is even possible to move single atoms with high accuracy by carefully "pushing" or "dragging" them with the tip of an STM. Since STM can be used as both a tool and an observation instrument on the nanometer scale it has been vital for the emergence of the nanosciences.

Related Topics:
K - Nanoscience

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