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One Step Closer to a Single-Molecule Device

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Molecule used to create the first single-molecule diode.

Columbia University engineering researchers have designed a new technique to create a single-molecule diode.

Credit: Latha Venkataraman

Under the direction of Columbia University professor Latha Venkataraman, researchers designed a new technique to create a single-molecule diode that can perform 50 times better than prior designs.

Venkataraman's group is the first to develop a single-molecule diode that may have real-world technological applications for nanoscale devices.

In order to develop a single-molecule diode, researchers designed molecules with asymmetric structures. However, "asymmetric molecular designs have typically suffered from very low current flow in both 'on' and 'off' directions, and the ratio of current flow in the two has typically been low. Ideally, the ratio of 'on' current to 'off' current, the rectification ratio, should be very high," researcher Brian Capozzi.

In order to overcome the issues associated with asymmetric molecular design, Venkataraman's team focused on developing asymmetry in the environment around the molecular junction. They surrounded the active molecule with an ionic solution and used gold metal electrodes of different sizes to contact the molecule. Their results achieved rectification ratios as high as 250:50 times higher than earlier designs.

The "on" current flow in their devices can be more than 0.1 microamps, which is a significant amount of current to be passing through a single molecule, Venkataraman notes.

From Columbia University
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