World's smallest diode developed

Scientists have developed the world's smallest diode - the size of a single molecule, an breakthrough that may help develop molecular electronic devices.
Continuous demand for more computing power is pushing the limitations of present day methods.
This need is driving researchers to look for molecules with interesting properties and find ways to establish reliable contacts between molecular components and bulk materials in an electrode, in order to mimic conventional electronic elements at the molecular scale.
An example for such an element is the nanoscale diode (or molecular rectifier), which operates like a valve to facilitate electronic current flow in one direction.

A collection of these nanoscale diodes, or molecules, has properties that resemble traditional electronic components such as a wire, transistor or rectifier.
"Creating and characterising the world's smallest diode is a significant milestone in the development of molecular electronic devices," said Yoni Dubi, a researcher in the Ben-Gurion University of the Negev (BGU) in Israel.

The emerging field of single molecule electronics may provide a way to overcome Moore's Law - the observation that over the history of computing hardware the number of transistors in a dense integrated circuit has doubled approximately every two years - beyond the limits of conventional silicon integrated circuits.

Researchers took a single DNA molecule constructed from 11 base pairs and connected it to an electronic circuit only a few nanometres in size.
When they measured the current through the molecule, it did not show any special behaviour.
However, when layers of a molecule called "coralyne," were inserted (or intercalated) between layers of DNA, the behaviour of the circuit changed drastically.
The current jumped to 15 times larger negative vs positive voltages - a necessary feature for a nano diode.
"In summary, we have constructed a molecular rectifier by intercalating specific, small molecules into designed DNA strands," said Bingqian Xu, from the University of Georgia.

Researchers constructed a theoretical model of the DNA molecule inside the electric circuit to better understand the results of the experiment.
"The model allowed us to identify the source of the diode-like feature, which originates from breaking spatial symmetry inside the DNA molecule after coralyne is inserted," the researchers said.
The study was published in the journal Nature Chemistry.