An atomic force microscope can be used to position individual atoms on a semiconductor surface at room temperature
The ability to manipulate individual atoms and molecules represents the ultimate limit in 'top-down' approaches to nanotechnology. The most famous example of single-atom manipulation was demonstrated in 1990, when two IBM researchers used a scanning tunnelling microscope to spell out the name of their company with 35 xenon atoms on a nickel surface. Now Oscar Custance of the National Institute of Materials Science in Tsukuba, and co-workers1 elsewhere in Japan, Spain and the Czech Republic have demonstrated a new variation on this theme with an atomic force microscope (AFM).
The interaction between an AFM tip and a surface can either be attractive or repulsive. In the past, Custance and co-workers have exploited attractive tip–surface interactions to create nanostructures on a surface, which they demonstrated by using tin atoms to spell out Sn — the atomic symbol for this element — on a germanium surface. Now they have exploited repulsive interactions between a silicon AFM tip and a monolayer of tin atoms on a silicon substrate to pattern the surface.
Whereas the approach based on attractive interactions involved using the AFM to move the atoms laterally on the surface, this latest work involves swapping a silicon atom at the end of the tip with a tin atom immediately below it on the surface. The ability of this 'vertical interchange' approach to produce complex patterns on a surface is demonstrated, as readers might have guessed, by writing the symbol Si with silicon atoms.
References
Sugimoto, Y. et al. Complex patterning by vertical interchange atom manipulation using atomic force microscopy. Science 322, 413–417 10.1126/science.1160601 (2008).
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Rodgers, P. Spelling it out. Nature Nanotech (2008). https://doi.org/10.1038/nnano.2008.338
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DOI: https://doi.org/10.1038/nnano.2008.338