The physical limits of how small a transistor can be have been tested following the creation of a single-molecule transistor, but not without great difficulty.

The concept of a single-molecule transistor was first proposed way back in 1990 by a team of researchers at IBM who managed to manoeuvre single atoms to form the company’s acronym with the help of a scanning tunnelling microscope (STM).

Now, however, a joint international research effort from Germany, Japan and the US has finally created a working single-molecule transistor by placing it on a semiconductor surface made of indium arsenide, with the findings published in Nature Physics.

To function, the single-molecule transistor can operate as a field-effect transistor, but only when it is surrounded by charged atoms that act as the transistor’s gate.

According to IEEE, the researchers encountered fewer challenges than had been expected as, typically, molecules on semiconductor surfaces are difficult to shift, but by using a molecule of copper phthalocyanine, thereby offering less resistance when using the STM, they encountered fewer issues.

“We created a certain electrostatic potential ‘landscape’ on the surface by placing [charged] atoms in a certain geometry through which we are moving the molecule on a fixed line,” said Stefan Fölsch, lead researcher on the project. “In each new position, the molecule feels a different electrostatic potential created by these atomic-scale gates.”

There is still a long way to go, however, before we can begin implementing almost-atomic level transistors commercially, largely due to the fact that the process in which it was created is still not really understood by science.

Equally challenging is the fact that it was created in an ultra-high vacuum at temperatures of just four degrees Kelvin (-269ºC).

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