Nano-LEDs emit full visible spectrum of light

Physicists through Taiwan possess designed along with fabricated nano-sized light-emitting diodes (LEDs) that emit light source spanning your whole visible spectrum. Although all the tiny full-color LEDs aren't meant for commercial lighting fixtures applications, they must be useful within high-resolution microscopy and additionally subwavelength photolithography.
A single nanodisk-nanorod LED viewed with a field-emission
scanning electron microscope. (Right) Some colors of light
emissions from nanodisk-nanorod LEDs - violet, blue, cyan,
green, and yellow - viewed with an optical microscope.
Image credit: Lu, et al. ©2011 American Institute of Physics

A researchers, Yu-Jung Lu, et ing., from National Tsing-Hua University or college in Hsinchu, Taiwan, have published their study to the nano-LEDs in a the latest issue of Applied Physics Letters.

The new nano-LEDs have a very good unique structure that is made of 40-nm-thick nanodisks sandwiched involving two layers of nanorods, creating a nanodisk-in-nanorod geometry. The nanodisks are made from indium gallium nitride (InGaN), a semiconducting material that is definitely widely used in LEDs and solar cells, while the nanorods are made from gallium nitride (GaN). Having said that, InGaN LEDs capable of emitting light belonging to the entire visible spectrum haven’t been achieved until now.

“The InGaN/GaN nanodisk/nanorod structure is just like a well-known quantum well structure, but in a lower dimensionality (reduction during lateral sizes), ” coauthor Shangjr Gwo, your physics professor at National Tsing-Hua University, told PhysOrg. com. “The InGaN nanodisks sandwiched regarding the p- and n-GaN regions be working as the full-color visible-light emitters anytime electrons and holes are injected through the p-n junction at a forward bias voltage. The electroluminescent light hails from the electron-hole recombination during the InGaN nanodisks. ”

As being the researchers explained, the essential to achieving full-color LEDs was first overcoming large lattice traces, which degrade long-wavelength emissions. The InGaN/GaN nanorod method resolves this issue as a consequence of strain relaxation in all the nanostructured geometry.

The researchers hope the full-color nano-LEDs work extremely well in high-resolution imaging techniques which could resolve ultrasmall subwavelength features of objects. To do this approach, these techniques must overcome the diffraction limit, the fundamental limit on imaging resolution as a result of the spreading out – and / or “diffraction” – of surf. Imaging techniques can find their way this limit by employing evanescent waves, which reveal home elevators objects’ subwavelength features, and decay exponentially away through the object. Due to the short range of the evanescent waves, imaging techniques that detect them depend on near-field optics.

One of such techniques is scanning near-field optical microscopy (SNOM), which operates on the all tiny probe to acquire and retrieve evanescent ocean. One of the biggest challenges in SNOM gets a light source that could be small and versatile enough to function on this probe, and that’s where new nano-LEDs come for. While previous research has demonstrated learn about using nano-LEDs on your probes, this is to start with that a nano-LED using a full-color range has already been available.

“For microscopy, we will use the nano-LED as being a localized excitation light source with a chosen wavelength to selectively inspire specific fluorescent molecules, ” Lu reported.

In their study, the researchers experimentally demonstrated making use of the nanodisk-in-nanorod LEDs for subwavelength photolithography, in which light is used to generate a pattern on a light-sensitive materials. They predict that, by way of fabricating the nano-LEDs upon the SNOM probe suggestions, they could achieve far better spatial control for near future subwavelength photolithography.

“For a applications of photolithography, the freedom of utilizing nano-LEDs at any wavelength broadens the options of photoresist and consists of the control of most of the photo-response, ” Lu reported.

More information: Yu-Jung Lu, et ing. “Single InGaN nanodisk lumination emitting diodes as full-color subwavelength lighting sources. ” Applied Physics Albhabets. DOI: 10. 1063/1. 3597211.

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