Single Molecule Switch Could Bring Us Closer to True Molecular Electronics

June 12, 2020 by Luke James

According to an international team of scientists, we could be one step closer to molecular electronics with a single molecule ‘switch’ that acts like a transistor and could potentially store binary information.

The team behind the switch believes that molecules like the ones discovered could hold 250 terabits of information per square inch. This is according to their study which shows that organic salt molecules can be switched to appear either bright or dark by using a small electrical current.

This switching between bright or dark provides binary information that can be written, read, and erased at room temperature and in normal air pressures. In contrast, much of the previous research that has gone into molecular electronics had to be conducted at very low temperatures in a vacuum.



Combining All Useful Features

In a statement, Dr. Stijn Mertens, Senior Lecturer in Electrochemical Surface Science at Lancaster University, who led the research study, said: “There is an entire list of properties that a molecule has to possess to be useful as a molecular memory…. Ours is the first example that combines all these [useful] features in the same molecule.”

These useful features are that aside from being switchable in both directions under ambient conditions, the molecule must be stable in the long-term in both the bright and dark state, and also spontaneously form highly ordered layers that are one molecule thick, a process known as self-assembly. 


Molecular switches seen under a scanning tunnelling microscope.

An image of the molecular switches seen under a scanning tunneling microscope. The light and dark squares can be used to provide binary information. Image credited to Dr. Kunal Mali, KU Leuven

An Important Proof of Concept

To prove their discovery’s worthiness, the research team used small electric pulses in a scanning tunneling microscope to switch individual molecules from bright to dark.

During switching, the electric pulse changes the way the organic salt’s cations and anions are stacked together, and this causes the molecule to appear either bright or dark. 

According to the Lancaster research team, the spontaneous ordering of these molecules is crucial. Via self-assembly, the molecules find their way into a two-dimensional crystal without the need for expensive manufacturing tools or processes that are currently used for electronics. “Because chemistry allows us to make molecules with sophisticated functions in enormous numbers and with atomic precision, molecular electronics may have a very bright future,” Dr. Mertens said.

Although the researchers are enthusiastic, they emphasize that they do not expect their molecules to be used in real-world applications but admit that the study is an “important” proof of concept that brings us one step closer to molecular electronics.