A scanning tunneling microscope, or STM, is a microscope commonly used in fundamental and industrial research.
Invented in 1981 by Gerd Binnig and Heinrich Rohrer from IBM's Zurich Research Center in Switzerland, it helped them win the 1986 Nobel Prize in Physics.
For an STM, good resolution is 0.1 nm lateral resolution and 0.01 nm depth resolution.
The high resolution of STMs enable researchers to examine surfaces at an atomic level.
The microscopes help scientists get a picture of how the atoms are arranged on a surface, by looking at the electron density of the surface atoms.
STMs are based on the idea of quantum tunneling, when a conducting tip is brought very close to the surface and a voltage difference between the tip and the surface is applied.
When the voltage difference is applied, electrons can tunnel through the vacuum between the tip and the surface, causing a tunneling current.
Using this principle, STMs work by passing a sharp wire made of metal over the surface that is to be examined.
The tip passes very close to the surface at the same time that the microscope applies an electrical voltage to the tip.
This creates an image that shows miniscule details on an atomic level.
There are several other microscopy techniques that researchers have developed based on the principles used for STMs.
STMs are helpful because they can give researchers a three dimensional profile of a surface, which allows researchers to examine a multitude of characteristics, including roughness, surface defects and determining things about the molecules such as size and conformation.
Other advantages of the scanning tunneling microscope include:
There are very few disadvantages to using a scanning tunneling microscope.
The two major downsides to using STMs are:
The electronics required for an STM are extremely sophisticated as well as very expensive.
Low cost and relatively low quality STMs start at approximately $8,000 but some people have actually built their own amateur STMs for much less than that amount.
However, professional quality STMs can range anywhere from $30,000 to $150,000 depending on the manufacturer and the extra parts included.
If you are interested in buying a scanning tunneling microscope, there are several reputable manufacturers from which you can make a purchase.
STM manufacturers include:
See Also: Atom under the Microscope for more info