Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Success in Self-Assembly of Quantum Dots with World’s Highest Density

19.07.2012
The NIMS Photonic Materials Unit is developing an advanced self-assembly technique for semiconductor quantum dots called droplet epitaxy, which is an original NIMS technology, and recently succeeded in the development of a new self-assembly technique for quantum dots with the world’s highest surface density, greatly exceeding the previously reported value.
Dr. Takaaki Mano, a Senior Researcher, Dr. Masafumi Jo, a Post Doctoral Fellow, and Dr. Yoshiki Sakuma, Group Leader of the Quantum Nanostructures Group, Photonic Materials Unit (Unit Director: Kazuaki Sakoda), National Institute for Materials Science (President: Sukekatsu Ushioda) are engaged in developing an advanced self-assembling technology for semiconductor quantum dots called droplet epitaxy, which is an original NIMS technology, and recently succeeded in the development of a new self-assembling technology for quantum dots with the world’s highest surface density, greatly exceeding the previously reported value. In addition, the NIMS researchers observed strong photoluminescence (PL) emission from the assembled quantum dots groups, suggesting that the developed technology is also effective for realizing excellent crystal quality.

Quantum dots have attracted heightened attention in recent years as a technology for achieving substantial improvement in the properties of semiconductor lasers and development of ultra-high efficiency photovoltaic cells based on a new operating principle. In the newly-developed technology, (1) use of a substrate with a high index surface, (2) formation and crystallization of gallium droplets at near-room temperature, and (3) suppression of the droplet coalescence by optimization of the amount of supplied gallium were introduced in the gallium arsenide (GaAs) quantum dot formation by droplet epitaxy. As a result, the NIMS team succeeded in self-assembly of GaAs quantum dots with an extremely high surface density of 7.3 x 1011/cm2 in a lattice-matched system. The team also discovered that defects originating in crystallization at near-room temperature can be restored by applying ingenuity to the heat treatment process for the crystallized quantum dots, and strong PL emission can be observed from the quantum dots.

Droplet epitaxy has attracted attention as the only method which enables self-assembly of quantum dots in lattice-matched systems, and in principle has the advantage that a large number of high quality quantum dot layers can be stacked in close proximity with maintaining high crystallinity. Therefore, if the ultra-high density in-plane quantum dots developed in this research are stacked in close proximity, it will be possible to produce quantum dot materials with extremely high volumetric density, which cannot be realized with the conventional technology. Thus, it is expected to be possible to achieve higher performance in optical and electronic devices which use quantum dots as a result of this research achievement.

Details of this research were published in the online edition of Applied Physics Letters, which is an American scientific journal in the field of applied physics, and are scheduled for publication in Vol. 100, No. 21 of the print edition.

Atomic force microscope (AFM) image of ultra-high surface density quantum dots formed by reducing the amount of gallium irradiation to 3 monolayer at a growth temperature of 30°C. An ultra-high surface density of 7.3 x 1011/cm2 was achieved. © NIMS

For more details:

Takaaki Mano
Senior Researcher
Photonic Materials Unit
National Institute for Materials Science
TEL:+81-29-859-2790

E-Mail: MANO.Takaaki=nims.go.jp
(Please change "=" to "@")

Masafumi Jo
Post-doctoral Researcher
Photonic Materials Unit
National Institute for Materials Science
TEL: +81-29-859-2702

E-Mail: JO.Masafumi=nims.go.jp
(Please change "=" to "@")

For general inquiry:

NIMS Public Relations Office
TEL:+81-29-859-2026
FAX:+81-29-859-2017

Mikiko Tanifuji | Research asia research news
Further information:
http://www.nims.go.jp
http://www.researchsea.com

More articles from Materials Sciences:

nachricht The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>