Team demonstrates quantum dots that assemble themselves

April 16, 2013

(Phys.org) —Scientists from the U.S. Department of Energy's National Renewable Energy Laboratory and other labs have demonstrated a process whereby quantum dots can self-assemble at optimal locations in nanowires, a breakthrough that could improve solar cells, quantum computing, and lighting devices.

A paper on the new technology, "Self-assembled Quantum Dots in a Nanowire System for ," appears in the current issue of the scientific journal Nature Materials.

Quantum dots are tiny crystals of semiconductor a few billionths of a meter in diameter. At that size they exhibit beneficial behaviors of such as forming electron-hole pairs and harvesting excess energy.

The scientists demonstrated how quantum dots can self-assemble at the apex of the /aluminum gallium arsenide core/shell nanowire interface. Crucially, the quantum dots, besides being highly stable, can be positioned precisely relative to the nanowire's center. That precision, combined with the materials' ability to provide quantum confinement for both the electrons and the holes, makes the approach a potential game-changer.

Electrons and holes typically locate in the lowest energy position within the confines of high-energy materials in the nanostructures. But in the new demonstration, the electron and hole, overlapping in a near-ideal way, are confined in the quantum dot itself at high energy rather than located at the lowest energy states. In this case, that's the gallium-arsenide core. It's like hitting the bulls-eye rather than the periphery.

The quantum dots, as a result, are very bright, spectrally narrow and highly anti-bunched, displaying excellent optical properties even when they are located just a few nanometers from the surface – a feature that even surprised the scientists.

"Some Swiss scientists announced that they had achieved this, but scientists at the conference had a hard time believing it," said NREL senior scientist Jun-Wei Luo, one of the co-authors of the study. Luo got to work constructing a quantum-dot-in-nanowire system using NREL's supercomputer and was able to demonstrate that despite the fact that the overall band edges are formed by the gallium Arsenide core, the thin aluminum-rich barriers provide both for the electrons and the holes inside the aluminum-poor quantum dot. That explains the origin of the highly unusual optical transitions.

Several practical applications are possible. The fact that stable quantum dots can be placed very close to the surface of the nanowires raises a huge potential for their use in detecting local electric and magnetic fields. The also could be used to charge converters for better light-harvesting, as in the case of photovoltaic cells.

The team of scientists working on the project came from universities and laboratories in Sweden, Switzerland, Spain, and the United States.

Explore further: Encouraging quantum dots to emit photons

More information: www.nature.com/nmat/journal/vaop/ncurrent/fig_tab/nmat3557_F4.html

Related Stories

Encouraging quantum dots to emit photons

August 5, 2010

(PhysOrg.com) -- One of the fields of great interest to scientists and researchers is that of using the quantum world to enhance various aspects of our lives. Advances in quantum cryptography make headlines, and scientists ...

Short-range scattering in quantum dots

October 20, 2010

Chinese researchers, reporting in the Journal of Applied Physics, published by the American Institute of Physics, have described a new breakthrough in understanding the way electrons travel around quantum dots. This might ...

Single quantum dot nanowire photodetectors

December 14, 2010

Moving a step closer toward quantum computing, a research team in the Netherlands recently fabricated a photodetector based on a single nanowire, in which the active element is a single quantum dot with a volume of a mere ...

Researchers demonstrate quantum dots that assemble themselves

February 11, 2013

(Phys.org)—Scientists from the U.S. Department of Energy's National Renewable Energy Laboratory and other labs have demonstrated a process whereby quantum dots can self-assemble at optimal locations in nanowires, a breakthrough ...

Recommended for you

An engineered surface unsticks sticky water droplets

August 31, 2015

The leaves of the lotus flower, and other natural surfaces that repel water and dirt, have been the model for many types of engineered liquid-repelling surfaces. As slippery as these surfaces are, however, tiny water droplets ...

Electrical circuit made of gel can repair itself

August 25, 2015

(Phys.org)—Scientists have fabricated a flexible electrical circuit that, when cut into two pieces, can repair itself and fully restore its original conductivity. The circuit is made of a new gel that possesses a combination ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.