Semiconductors are made by adding minute amounts of a dopant, such as antimony, to highly pure crystals of silicon or germanium. Greater precision in controlling such doping would enable the production of semiconductors with superior properties. In this experiment, the mixing of minute amounts of an element into a different material was done at the level of individual atoms.

The material used by the group to accept the dopant was a surface layor of single tin atoms on a silicon substrate. They placed the probe of an atomic force microscope near this surface. Atomic force microscopes can be used with nonconductors and are fitted with fine probes having sharp tips on the micro level. If such a probe is brought close to the material to be observed, the atomic force acts between the probe tip and target material, and the material surface is observed by measuring this atomic force.

In this study, the research group discovered a phenomenon in which a single atom at the probe tip switches places with a single atom on the material surface when the probe approaches the material surface under certain conditions. The group encountered difficulty when it tried to make this phenomenon occur for specific atoms on the material surface. However, they were able to overcome this by improving the adjustment accuracy of the probe in a horizontal position to the atomic level of ±0.01 nanometer and increasing the detection sensitivity of the atomic force acting between the probe tip and surface atoms down to the microscopic level of 10 piconewtons.

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