Nanocrystals Emit Light by Tunneling Electrons

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Tiny device out of silver crystals to generate light by tunnelling electrons through a tiny barrier

Engineers at University of California San Diego have built a nanosized device out of silver crystals that can generate light by tunnelling electrons through a tiny barrier. The work brings plasmonics research a step closer to realising compact light sources for high-speed, optical data processing and other on-chip applications.

Morphology and working of the device

The device is a tiny bow tie shaped plasmonic nanostructure consisting of two cuboids, single crystals of silver joined at one corner. Connecting the corners is a 1.5-nanometer wide barrier of insulator made of a polymer called polyvinylpyrrolidone (PVP).

This tiny metal insulator metal (silver PVP silver) junction is where the action occurs. Electrodes connected to the nanocrystals allow voltage to be applied to the device. As electrons tunnel from a corner of a silver nanocrystal through the tiny PVP barrier, they transfer energy to surface plasmon polaritons. Then the electromagnetic waves that travel along the metal-insulator interface convert that energy to photons.

But what makes this particular junction more efficient at tunnelling electrons inelastically is its geometry and extremely tiny size. By joining two silver single crystals together at their corners with a tiny barrier of an insulator in between results in the conversion of electronic energy to light.

With additional work, the team aims to boost efficiency and are exploring different geometries and materials for future studies.