Published in the July 1 issue of Nature, their research builds on work by the same Maryland research team published in March in the journal Science (3-26-10). According to the authors and outside experts, the new findings further advance the promise these new nanostructures hold for quantum computing and for new, more efficient, energy generation technologies (such as photovoltaic cells), as well as for other technologies that are based on light-matter interactions like biomarkers.
"The real breakthrough is that we use a new technology from materials science to 'shed light' on light-matter interactions and related quantum science in ways that we believe will have important applications in many areas, particularly energy conversion and storage and quantum computing," said lead researcher Min Ouyang, an assistant professor in the department of physics and in the university's Maryland NanoCenter. "In fact, our team already is applying our new understanding of nanoscale light-matter interactions and advancement of precise control of nanostructures to the development of a new type of photovoltaic cell that we expect to be significantly more efficient at converting light to electricity than are current cells."
Ouyang and the other members of the University of Maryland team -- research scientist Jiatao Zhang, and students Kwan Lee and Yun Tang -- have created a patent-pending process that uses chemical thermodynamics to produce, in solution, a broad range of different combination materials, each with a shell of structurally perfect mono-crystal semiconductor around a metal core. In the research published in this week's Nature, the researchers used hybrid metal/semiconductor nanostructures developed through this process to experimentally demonstrate "tunable resonant coupling" between a plasmon (from metal core) and an exciton (from semiconductor shell), with a resulting enhancement of the Optical Stark Effect. This effect was discovered some 60 years ago in studies of the interaction between light and atoms that showed light can be applied to modify atomic quantum states.
Ouyang and his colleagues agree that their new findings were made possible by their crystal-metal hybrid nanostructures, which offer a number of benefits over the epitaxial structures used for previous work. Epitaxy has been the principle way to create single crystal semiconductors and related devices. The new research highlights the new capabilities of these UM nanostructures, made with a process that avoids two key constraints of epitaxy -- a limit on deposition semiconductor layer thickness and a rigid requirement for "lattice matching."
The Maryland scientists note that, in addition to the enhanced capabilities of their hybrid nanostructures, the method for producing them doesn't require a clean room facility and the materials don't have to be formed in a vacuum, the way those made by conventional epitaxy do. "Thus it also would be much simpler and cheaper for companies to mass produce products based on our hybrid nanostructures," Ouyang said.
"Tailoring light-matter-spin interactions in colloidal hetero-nanostructures" Jiatao Zhang, Yun Tang, Kwan Lee, Min Ouyang, Nature, July 1, 2010.
This work was supported by the Office of Naval Research, the National Science Foundation (NSF), and Beckman Foundation. Facility support was from Maryland Nanocenter and its Nanoscale Imaging, Spectroscopy, and Properties Laboratory, which is supported in part by the NSF as a Materials Research Science and Engineering Centers shared experiment facility.Media Contact
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