Atom-scale manipulation breakthrough by Swiss researchers

15 July 2014
By Anna Vega
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20 bromine atoms were positioned on a sodium chloride surface using the tip of an atomic force microscope at room temperature.

20 bromine atoms were positioned on a sodium chloride surface using the tip of an atomic force microscope at room temperature.

The first successful systematic atomic manipulation on an insulating surface at room temperatures has been achieved and presented by international researchers at the University of Basel, thereby taking the manipulation of atoms to a new level.

It is significant because it opens up the possibility for the creation of next generation atomic-scale data storage devices and logic circuits, and the fabrication of a new generation of electromechanical systems.

The scientists used the tip of an atomic force microscope and placed single bromine atoms on a sodium chloride (NaCl) surface to construct the shape of the Swiss cross. The tiny cross is made of 20 bromine atoms and was created by exchanging chlorine with bromine atoms. It measures only 5.6nm square and represents the largest number of atomic manipulations ever achieved at room temperature.

“Essentially, you can think about it as an ultra-dense storage medium, where information can be stored with a few atoms,” Head of Research, Ernst Meyer, explained.

“Alternatively, one may think to create logic circuits as in a processor. NaCl is an insulator. If we can write conducting lines, one may build a network.” 

Meyer said one can imagine combining mechanical motions with electrical circuits: “For example, to create high accuracy frequency standards, similar to quartz in a watch or the time base in a computer,” he said.

The fabrication of artificial structures on an insulator at room temperature was a long-standing challenge. While several atomic manipulations were previously demonstrated on conducting and semi-conducting surfaces, these were mainly achieved under very low temperatures. Previous attempts to fabricate artificial structures on insulators at room temperatures were uncontrollable and did not deliver the desired results.

 

“It is essential that the bromine atoms remain embedded in the NaCl-lattice. If they would sit on top, diffusion would be too large,” explains Meyer.

Together with theoretical calculations the research team was able to identify the novel manipulation mechanisms to fabricate unique structures at the atomic scale. So what is the novel manipulation mechanism that was identified?

“The manipulation process is an exchange mechanism between bromine and chlorine atoms mediated by the probing tip. It is quite similar to people in a full cinema who change places,” explains Meyer.

The research team included Shigeki Kawai and Ernst Meyer from the University’s Department of Physics, together with teams from Finland and Japan.

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