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Nanotube-Based Tunneling Field Effect Transistor Offers Semiconductor-Free Switching

Researchers at Michigan Technological University (MTU) have developed a method for producing a tunneling field effect transistor (TFET) that overcomes a key obstacle to their adoption: the need to be operated at cryogenic temperatures. Eliminating semiconductor materials in the design of their nanotube-based TFET has allowed the MTU researchers to fabricate a device that can operate at room temperatures and offers the added feature of flexibility.

In research explained in an article published in the Nature journal Scientific Reports, the MTU researchers, led by Yoke Khin Yap, used iron quantum dots in combination with functionalized boron nitride nanotubes (BNNTs) to create flexible tunneling channels in TFET devices.

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Nanomembrane May Bring Rechargeable Lithium-Metal Batteries Back

Researchers at Cornell University, in Ithaca, N.Y., may have found a way to bring the long-moribund prospects of rechargeable lithium-metal batteries back from the dead with a novel nanostructured membrane that could make the batteries both safe and efficient.

In research described in the journal Nature Communications, the Cornell researchers looked anew at the problem that has been plaguing the prospects of rechargeable lithium-metal batteries: growths, referred to as dendrites, that over time branch out of the anode, into the electrolyte, and eventually expand to the point where they actually bridge the gap between the two electrodes and cause the battery to short out—or even worse.

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Cheap Cubic-Boron Nitride Could Enable Next Gen Smart Grid

Researchers at North Carolina State University (NCSU), led by Jay Narayan, have developed a new method for converting hexagonal-boron nitride (h-BN) directly into cubic-boron nitride (c-BN) that is faster and less expensive than previous processes and promises to make a material that is more viable for high-power electronics, transistors and solid-state devices.

Boron nitride (BN) comes in four basic forms. Two of these forms of boron nitride, namely hexagonal-boron nitride (h-BN) and cubic-boron nitride (c-BN), represent the two most attractive forms of BN for electronic applications because their structures and properties are quite similar to both graphite and diamonds. Like diamonds, c-BN has very good thermal properties for integrated circuits as well as high-frequency power capabilities that compare favorably with silicon.

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World's First Single-Atom Optical Switch Fabricated

You may have heard of the single-atom transistor that thumbed its nose at Moore’s Law once and for all. But that transistor was based on the electron, a relative slow poke. What if you could develop a single-atom transistor based on the movement of photons, which travel at the speed of light? Now that would be both small and fast.

Now researchers at ETH Zurich Switzerland have developed the equivalent of a single-atom photonic transistor by fabricating the world’s first single-atom optical switch

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Graphene Cages Cover Silicon Anodes for High Capacity Batteries

Ever since researchers first discovered that the charge life of Li-ion batteries could be improved by a factor of ten by replacing graphite on the anodes with silicon, there has been a steady stream of research aimed at making silicon actually work as an anode material in real-world batteries.

This has not been easy. The main problem has been that as they take on charge, the anodes swell enormously; when they discharge, they shrink, and the silicon cracks. Another issue has been that when lithium ions travel from anode to cathode through the electrolyte, they create a coating on the electrodes that reduces the battery’s performance.

One researcher who has been focused on developing a practical silicon-based anode is Yi Cui from both Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory. Now Cui and a team of researchers from both Stanford and SLAC have developed a new approach to using silicon in the anodes of Li-ion batteries—one that might not only be technologically possible, but also commercially viable.

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Charge Transport in Plastics Increased One Thousand Times

One of the factors that has kept conjugated semiconducting polymers from being even more effective in applications such as organic photovoltaics (OPVs) and organic light-emitting diodes (OLEDs) is the materials’ poor charge carrier mobility. Basically, charge doesn’t move through plastic—even the conjugated variety—as well as it does through silicon. The result is high losses and poor performance.

Nanomaterials such as graphene have been offered up as additives to increase carrier mobility in polymers

Now researchers at Umeå University in Sweden have developed a novel technique for improving the charge transport mobility of a polymer by more than a thousand times. The researchers were able to achieve this enormous increase without any doping of the polymer; instead, they controlled the orientation of the crystallite formations in the polymer.

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Flexible Pressure Sensors Stay Accurate Even When Bent

Research has shown that nanofibers can be fashioned into a pretty effective flexible pressure sensor. We have also seen carbon nanotubes structured into pyramid shapes  or just sprayed over silicone to produce flexible pressure sensors.

Now an international team at the University of Tokyo has produced nanofibers made from a mix of carbon nanotubes and graphene that overcomes a big problem facing flexible pressure sensors—that they lose their accuracy after being bent or deformed. The resulting pressure sensor could be used to better detect breast tumors, its inventors suggest.

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Detergent Triggers Self Assembly of Two-Dimensional Zinc Oxide

There is a fairly large number of materials that might have some pretty attractive properties if they could be made into monolayer, two-dimensional (2-D) sheets. Unfortunately, unlike graphene, which is fabricated by peeling away layers from bulk graphite, these other materials don’t have a multi-layered source. But now the fabrication of these materials has become a possibility through a novel “bottom-up” production technique whose development may have just changed the future of 2-D materials in electronics.

Researchers at the University of Wisconsin-Madison (UW-Madison) have developed a technique in which a zinc oxide monolayer self assembles in a liquid with the help of a surfactant.  After six years of trial-and-error testing with different surfacants, the UW-Madison researchers believe they have found the right mix.

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Nanoscale Thermal Interfaces Eliminate Overheating in Future Photonic Circuits

For years the prospects of photonic circuits—those that use photons instead of the electrons—were mired in a lack-of-space problem: A photonic system couldn’t get any smaller than a wavelength of light, about 1000 nanometers for infrared, while some dimensions of today’s transistors are one one-hundedth that size.

Enter plasmonics in which devices exploit the oscillating waves of electrons that are generated when photons hit a metal surface. Plasmonic-based approaches confine the size of the wavelength and makes it possible to fabricate smaller devices. But plasmonics for photonic circuits has some drawbacks too, namely surface-of-the-sun type heat.

Now researchers at Moscow Institute of Physics and Technology's (MIPT) Laboratory of Nanooptics and Plasmonics have found a solution to the problem of overheating of active plasmonic components using industry-standard heatsinks. If this solution proves successful, the prospects for photonic circuits will have brightened significantly.

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Graphene Offers Emission Tunability for Terahertz Lasers

Despite the myriad uses we have for lasers, once the wavelengths of light have been set for a laser, it’s usually fixed for that device.

Now researchers at the University of Manchester in the UK have demonstrated that they can tune a terahertz laser so that there is reversible control over its emission. They’ve done so by combining a graphene sheet with a terahertz quantum cascade laser. The key to this control over the laser’s emission is manipulating the doping of the graphene layer to change the concentration of charge carriers.

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IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

Dexter Johnson
Madrid, Spain
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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