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December, 2012


Better Electronics Through Invisibility


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ties. The composite structures used for cloaking cause light beams to bend around an object and then meet on the other side, resuming their original path —making the object ap- pear to be invisible. “We were inspired by this idea,”


says Chen, the Carl Richard Soder- berg Professor of Power Engineering at MIT, who decided to study how it might apply to electrons instead of light. But in the new electron-cloak- ing material developed by Chen and his colleagues, the process is slightly different. The MIT researchers modeled


nanoparticles with a core of one ma- terial and a shell of another. But in this case, rather than bending around the object, the electrons do actually pass through the particles; their paths are bent first one way, then back again, so they return to the same trajectory they began with.


In computer simulations, the


concept appears to work, Liao says. Now, the team will try to build actu- al devices to see whether they per- form as expected. “This was a first step, a theoretical proposal,” Liao says. “We want to carry on further research on how to make some real devices out of this strategy.” While the initial concept was


developed using particles embedded in a normal semiconductor substrate, the MIT researchers would like to see if the results can be replicated with other materials, such as two-di- mensional sheets of graphene, which might offer interesting additional properties.


Optimizing Materials The MIT researchers’ initial im-


petus was to optimize the materials used in thermoelectric devices, which produce an electrical current from a temperature gradient. Such devices require a combination of characteris- tics that are hard to obtain: high electrical conductivity (so the gener-


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ated current can flow freely), but low thermal conductivity (to maintain a temperature gradient). But the two types of conductivity tend to coexist, so few materials offer these contra- dictory characteristics. The team’s simulations show this electron-cloak- ing material could meet these re- quirements unusually well. The simulations used particles


a few nanometers in size, matching the wavelength of flowing electrons and improving the flow of electrons at particular energy levels by orders of magnitude compared to traditional doping strategies. This might lead to more efficient filters or sensors, the researchers say. As the components on computer chips get smaller, Chen says, “we have to come up with strategies to control electron trans- port,” and this might be one useful approach. The concept could also lead to a


new kind of switch for electronic de- vices, Chen says. The switch could operate by toggling between trans- parent and opaque to electrons, thus turning a flow of them on and off. “We’re really just at the beginning,” he says. “We’re not sure how far this is going to go yet, but there is some potential” for significant applica- tions.


This research was funded by the


U.S. Department of Energy (DOE) through MIT’s Solid-State Solar- Thermal Energy Conversion center, a DOE Energy Frontier Research Center.


Contact: Massachusetts Insti-


tute of Technology, 77 Massachu- setts Ave., Bldg. 11-400, Cambridge, MA 02139-4307 % 617-253-1682 Web: http://web.mit.edu r


Contents


Tech-Op-Ed ........................... 4 Tech Watch ........................... 10 People.................................... 12 Business News........................ 14 Business Briefs....................... 15 Management........................ 16 EMS .................................... 18 ElectronicMfg. Prods............. 22 Production.......................... 42 Partnering........................... 44 Distribution........................ 46 New Products..................... 58 High-Tech Events................... 92 Editorial Calendar............... 92 Advertisers Index............... 94


Special Focus: Test and Measurement........... 48


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