The new nanostructured approach using solution-based chemical synthesis is in contrast to traditional nanolithography techniques. The research comes from the University of California San Diego. Through this method the researchers have managed to to assemble silver nanocrystals into tiny metal–insulator–metal junctions.
The new technology, as EE News reports, is comprised of two single crystals silver cuboids connected at one corner. The device is a tiny bow-tie-shaped plasmonic nanostructure. These crystals are separated by a 1.5 nanometer thin insulating polymer (made from PolyVinylPyrrolidone, a water-soluble polymer). The study showed that by applying a controlled voltage across the tiny junction enables electrons to move from one corner to the next corner, through the through the PolyVinylPyrrolidone barrier.
This functions to transfer some of the energy from the electrons to surface plasmon polaritons across a metal-insulator interface. Here the effect is to radiate that energy into photons.
Because of the small size, and due to the precise geometric arrangement, the technology is very efficient at tunnelling electrons inelastically. In practice, this means greater amounts of energy can be transferred from the electrons.
The scientists have found a more efficient light generation of up to 2 percent, which represents an improvement of two orders of magnitude in relation to conventional light generating systems.
The optimize the light emitting device architecture, the researchers applied computational methods together with numerical simulations. These simulations demonstrated that the color of the emitted light was a factor of the geometry of the junction structures. By working on this, the researchers are able to alter the size and shape of the crystals that they synthesise in solution, generating improved and energy efficient light.
In the longer term, this could lead to a new generation of ultra-compact optical sources. The new plasmonic nanostructure is described in a paper headed “Efficient light generation from enhanced inelastic electron tunnelling“, which is published in Nature Photonics.
