Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum dots see in the dark

15.06.2004


USC/UT ’Quantum Dot’ nanodevices promise improved night vision goggles, medical sensors and more



Researchers at the University of Southern California and the University of Texas at Austin have built and tested a device based on nanostructures called quantum dots that can sensitively detect infrared radiation in a crucial wavelength range. Quantum dot IR receptor unit.

The atmosphere is opaque to most infrared, but it is transparent for a narrow "window" between 8 and 12 microns. Night vision goggles, military target tracking devices and environmental monitors utilize this range of wavelengths.


Anupam Madhukar, holder of the Kenneth T. Norris Chair in the USC Viterbi School of Engineering with appointments in the departments of materials science, biomedical engineering and physics, says "a class of existing infrared detectors are based on what is called ’quantum well’ technology. But we have created a detector based on different physics--quantum dot physics--that works at least as well and has the potential to perform better."

Madhukar worked with Joe C. Campbell, who holds the Cockrell Family Regents Chair in the UT Austin College of Engineering’s department of electrical and computer engineering. The two engineers described the device in the April 24 issue of Applied Physics Letters.

The device uses self-assembled "quantum dots," island-like pyramidal structures made of semiconductors. Each dot has a core of indium arsenide surrounded by gallium arsenide and an indium-gallium arsenide alloy. A single dot is approximately 20 nanometers (2 millionths of a centimeter) in base size and about 4 nanometers in height.

The three-dimensional confinement of electrons within these structures creates unique, characteristic behavior. By using varying proportions of the materials and changing synthesis procedures, engineers can tailor quantum dots for use in lasers, detectors, optical amplifiers, transistors, tunneling diodes, and other devices.

"Quantum dots are emerging as the most viable semiconductor nanotechnology for future higher performance communication systems, biomedical imaging, environmental sensors, and infrared detection," said Madhukar.

Unlike their alternatives, quantum dot infrared detectors strongly absorb radiation shining perpendicular to the plane of an array of quantum dots.

By contrast, the alternate quantum well detectors don’t pick up radiation that shines straight down on them. To achieve this "necessitates additional processing steps," Madhukar said. This increases the cost of the well detectors.

When the engineers benchmarked the new device using standard tests, its detectivity was nearly 100 times higher than the previously reported peak for quantum dot systems. The new range is competitive with the corresponding values for the well-established quantum well infrared photo detectors.

"It is about an order of magnitude lower than a third technology, mercury-cadmium-telluride material based infrared detectors. These now provide the best available performance, but suffer from materials uniformity and long-term stability issues," said Campbell.

The researchers expect that placing the dot arrays in a configuration called a "resonant cavity," which traps the radiation and bounces it back and forth between mirroring walls, will make them more sensitive.



The U.S. Air Force Office of Scientific Research supported the research under the U.S. Department of Defense sponsored Multidisciplinary University Research Initiatives (MURI) Program in Nanoscience.

Contacts: A. Madhukar, USC, 213-740-4323; Joe C. Campbell, UT Austin, 512-471-9669]

Eric Mankin | EurekAlert!
Further information:
http://www.usc.edu/

More articles from Process Engineering:

nachricht Diamond watch components
18.06.2018 | Schweizerischer Nationalfonds SNF

nachricht Quick and safe laser joining of steel-aluminum mixed connections
05.06.2018 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Creating a new composite fuel for new-generation fast reactors

20.06.2018 | Materials Sciences

Game-changing finding pushes 3D-printing to the molecular limit

20.06.2018 | Materials Sciences

Could this material enable autonomous vehicles to come to market sooner?

20.06.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>