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NEWS | Sept. 26, 2013

Dr. Alexander Efros Receives the E.F. Gross Medal for Pioneering Nanocrystal Research

By Daniel Parry

U.S. Naval Research Laboratory (NRL) research physicist, Dr. Alexander Efros, is one of three recipients of the 2013 E. F. Gross Medal, awarded by the D. S. Rozhdestvensky Optical Society for pioneering work in the discovery and theoretical description of quantum size effects in the optical spectra of semiconductor nanocrystals.

Efros is most notably recognized for his work on the tunable emission spectra of nanocrystals that launched a revolution in the development of affordable, highly efficient devices for use as sensors, imaging, and displays and his contributions to the theory of nanocrystal quantum dots to include the establishment of the basic model used for describing their electronic and optical properties.

In the early 1980s Efros and his colleagues, A. I. Ekimov and A. A. Onuschenko, discovered semiconductor nanocrystals while studying doped glasses. They also explained the origin of the size-dependent optical properties of nanocrystals, and established that nanocrystals act as 'artificial atoms' that opened the door to a new class of optical materials.

Like atoms, nanocrystals have discrete optical energy spectra that are tunable over a wide spectral range by varying their size. At the same time these atoms can be manipulated with nanometer precision to form nanocrystal molecules and solids. Nanocrystals also can serve as dopants in nanocrystalline solids. As a result, researchers now have an unlimited number of new atomic elements available to create new materials.

Based on size controlled tunable emission spectra and great structural and chemical flexibility, the nanocrystals have potential in the creation of a new class of tunable quantum dot lasers and light emitting diodes that function from the far infrared to deep ultraviolet wavelength ranges. An additional application is the labeling of biological molecules by nanocrystals, which are being developed as ultra-sensitive detectors and sensors for use in neuron and drug transport imaging, and the detection of dangerous chemical agents.

The high optical stability of the nanocrystals allow for higher efficiency in quantum dot displays. In very recent developments of this area, researchers from Samsung Electronics demonstrated in 2012 a full-color quantum-dot display monitor that is brighter than liquid-crystal displays and consumes less than a fifth of the power.

Receiving a Master of Science degree in physical engineering in 1973 and a Ph.D. in physics in 1978, both from the Technical University in Leningrad, USSR, Efros became senior researcher at the Ioffe Institute in Leningrad. From 1990 to 1992 he was senior researcher at the Technical University of Munich and a visiting scientist at Massachusetts Institute of Technology (MIT). In 1993 Efros came to NRL as a consultant and in 1999 become senior researcher in NRL's Materials Science and Technology Division.

Efros has authored and co-authored more than 180 articles in refereed journals and holds two patents. He has given more than 70 invited talks at international meetings and more than 180 at various universities and laboratories. He is co-editor of two books on nanoscale semiconductors and co-organizer of many conferences on this topic and is a Fellow of the American Physical Society. Efros has received five Alan Berman publication awards, an NRL Patent Award (2003), the NRL Sigma Xi Award for Pure Science (2006), the R.W. Wood Prize of the Optical Society of America (2006, with L. E. Brus and A. I. Ekimov), the Humboldt Research Award for Senior U.S. Scientists (2008), and the Dolores M. Etter Top Navy Scientists and Engineers of the Year Award (2009).

Established in 2012 by the Russian Optical Society, the E. F. Gross Medal is awarded annually for pioneering discoveries and fundamental contributions to the fields of optics and solid-state spectroscopy. The medal was established in honor of Professor Evgenii Fedorovich Gross (1897- 1972), an outstanding physicist and member of the USSR Academy of Sciences, who laid the foundations of modern solid-state optical spectroscopy in the USSR.

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