Surface Science Group
How STM Works
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Surface Science Group |
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STMThis stands for Scanning Tunneling Microscopy which is a technique that lets us image individual atoms. By looking at where the atoms on a surface are located relative to other atoms, we can figure out how they are bound to each other.
We can also make movies! We see the atoms moving around as they break and make bonds and settle down with their favorite friends. Yes, some become stars of the little screen. |
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How the STM Works |
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We use an STM whose design was developed in Aarhus. The STM brings a sharp tip, usually made of tungsten, really close to the surface of a sample. When it is a few Angstroms away (an atom is about 1 Angstrom) electrons jump across the gap bewteen the tip and surface.
This "tunneling" current lets us measure how close the tip is. When we scan the tip across the sample, atoms that are sticking out from the surface give a larger current. We can take this current map and make a picture of where the atoms are all located. The scanning and tip approach are all accomplished with piezoelectric actuators which allow us to move the tip with extreme precision - fractions of the size of atoms. Check out the detailed schematic of the Aarhus STM. |
The actual motion is accomplished using a piezoelectric tube. This material expands or contracts when a voltage is applied to it. By applying potentials to opposite sides (where metal pads are located) the STM tip is translated from side to side. There are also contacts that allow us to expand or contract the length of the tube which provides the exquisitely sensitive adjustment of the distance between the sample and the tip. |
 Graphic from http://www.fysik.dtu.dk/~horch/ |
This image shows individual atoms on an FeAl crystal that has been oxidized to form a surface layer of Al2O3. For more STM data check out our Research links |
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This work supported in part by NSF-DMR under IMR 0216875 and 0216134 and by NSF-DECS under NER 0210583 and by the Louisiana State Board of Regents |