STM: Some Applications


Here are some examples of using STM in both surface science studies and advanced technological applications.

Surface Science

The invention of STM have left a great impact on surface science. Uses of STM to study metals and semiconductors surface can provide non-trivial real space information. especially in studying semiconductor such as Si(100) surface, which is the technologically important Si substrate material for microelectronics device fibrication. The STM image of Si(100) surface shown below gives direct confirmation of dimers formation during surface reconstruction, although it has been previously suggested by theoretical calculation and other experimental observations.

Si (001)

Here are the bias-dependent STM images, the top left image, with positive bias to the tip, the right one, with negative bias to the tip. The images directly reflect the spatial distribution of the occupied pi -bonding state is between the dimer atoms, while the unoccupied pi star -antibonding states localized away from the dimer. The bottom pictures depict the model of the reconstruction of the bulk-terminated (1x 1) lattices into a (2 x 1) reconstruction via dimerization, the large dots represent atoms on top layer, while small dots are atoms of second layer.




Si(100) surface model





Metrological Applications

The microtopography and nanotopography of a surface is crucial in many applications, such as for high precision optical components and disk drive surface roughness of machined or ground surfaces in area where such a finish is crucial.

This is the STM image of and individual turn mark on a diamond-turned Al substrate to be used for subsequent magnetic film deposition for a high capacity hard disc drive. The image obtained by scanning electron microscope (SEM) is shown to the right for comparison. The high spatial resolution of STM provides an important complement to the SEM.



stm image of harddisk surface SEM image of hard disk surface



Manipulation of Atoms




Formation of quantum Corral

One innovative applications of STM recently found is manipulation of atoms. Here is an example, Iron atoms are placed on Cu(111) surface at very low temperature (4K), Iron atoms are first physisorbed on the Su surface, then the tip is placed directly over a physisorbed atom and lowered to increase the attractive force by increasing the tunneling current, the atom was dragged by the tip and moves across the surface to a desired position. Then, the tip was withdrawn by lowering the tunneling current.

These STM images show the steps of "quantum corral" formation






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Author: Tit-Wah Hui email: <thui@uoguelph.ca>
Curator: Dan Thomas email: <thomas@chembio.uoguelph.ca>
Last Updated: Mon, Apr 14, 1997 15:06 EST