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Rice University researchers have discovered a simple method to make films of highly aligned carbon nanotubes. The films can be separated from their backgrounds and show potential for use in electronic and photonic applications. (Credit: Jeff Fitlow/Rice University)

A simple filtration process helped Rice University researchers create flexible, wafer-scale films of highly aligned and closely packed carbon nanotubes. Scientists at Rice, with support from Los Alamos National Laboratory, have made inch-wide films of densely packed, chirality-enriched single-walled carbon nanotubes. In the right solution of nanotubes and under the right conditions, the tubes assemble themselves by the millions into long rows that are aligned better than once thought possible, the researchers reported. The thin films offer possibilities for making flexible electronic and photonic (light-manipulating) devices, said Rice physicist Junichiro Kono, whose lab led the study. Think of a bendable computer chip, rather than a brittle silicon one, and the potential becomes clear, he said. The Rice lab is closing in, Kono said, but the films reported in the current paper are “chirality-enriched” rather than single-chirality. A carbon nanotube is a cylinder of graphene, with its atoms arranged in hexagons. How the hexagons are turned sets the tube’s chirality, and that determines its electronic properties. Some are semiconducting like silicon, and others are metallic conductors. A film of perfectly aligned, single-chirality nanotubes would have specific electronic properties. Controlling the chirality would allow for tunable films, Kono said, but nanotubes grow in batches of random types.

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Stanford and IBM researchers inserted chain-like molecules of polystyrene—the same material in a styrofoam coffee cup—between layers of nanocomposites to make these materials tougher and more flexible. (Image Credit: Dauskardt Lab, Stanford University)b, Stanford University)

Stanford and IBM researchers inserted chain-like molecules of polystyrene—the same material in a styrofoam coffee cup—between layers of nanocomposites to make these materials tougher and more flexible.(Image Credit: Dauskardt Lab, Stanford University)

By slipping springy polystyrene molecules between layers of tough yet brittle composites, researchers made materials stronger and more flexible, in the process demonstrating the theoretical limits of how far this toughening technique could go. Researchers at Stanford and IBM have tested the upper boundaries of mechanical toughness in a class of lightweight nanocomposites toughened by individual molecules, and offered a new model for how they get their toughness. The potential applications for nanocomposites cut across many industries, from computer circuitry to transportation to athletics. They could even revolutionize spaceflight with their ability to withstand tension and extreme temperatures. The study was led by Reinhold Dauskardt, a professor of materials science and engineering at Stanford University, and Geraud Dubois, of IBM's Almaden Research Center. The study was sponsored by the Air Force Office of Scientific Research.

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The recently launched EU ASCENT project recently held its 1st Users Workshop at the XXIV International Scientific Conference ‘Electronics - ET2015’ in Bulgaria. Attendees heard how ASCENT will enable access to the unique nanoelectronics infrastructure of three of Europe’s premier research centres. The Users Workshops are an important part of the ASCENT mission to support a vibrant nanoelectronics research community across Europe. The three partners (Tyndall, imec and CEA-Leti) will provide researchers with access to advanced device data, test chips, flexible fabrication and characterisation equipment. ASCENT will enable the nanoelectronics modelling-and-characterisation research community to explore exciting new developments in industry and meet the challenges created in an ever-evolving and demanding digital world. ASCENT enables Europe’s world-leading atomic scale device, TCAD and compact modelling community to perform the systematic studies that are required to develop nanoscale design methodologies and to identify the impact of quantum effects on sub-10 nm device performance. It provides an interface to global industrial leaders in nanoelectronics through the Industry Innovation Committee and through activities designed to transfer IP and technology uptake from the supported research activities. The results from the access activities will be fed back to device manufacturers to future improve the nanoscale devices being developed. ASCENT will reach out to the research community through a co-ordinated marketing campaign and will offer a simple single access route to the advanced technologies provided. ASCENT will provide technical and logistical support to Users and the results of the Access activities will be published and shared at User Workshops enabling strong interaction between the Users and Providers.

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Scientists announced the first observation of a dynamic vortex Mott transition, which experimentally connects the worlds of quantum mechanics and classical physics and could shed light on the poorly understood world of non-equilibrium physics. (Image courtesy Valerii Vinokur/Science, Argonne National Lab Press Release)
An international team of researchers, including the MESA+ Institute for Nanotechnology at the University of Twente in The Netherlands and the U.S. Department of Energy’s Argonne National Laboratory, have announced the observation of a dynamic Mott transition in a superconductor. 
The discovery experimentally connects the worlds of classical and quantum mechanics and illuminates the mysterious nature of the Mott transition. It also could shed light on non-equilibrium physics, which is poorly understood but governs most of what occurs in our world. The finding may also represent a step towards more efficient electronics based on the Mott transition.
Since its foundations were laid in the early part of the 20th century, scientists have been trying to reconcile quantum mechanics with the rules of classical or Newtonian physics (like how you describe the path of an apple thrown into the air—or dropped from a tree). Physicists have made strides in linking the two approaches, but experiments that connect the two are still few and far between; physics phenomena are usually classified as either quantum or classical, but not both.
One system that unites the two is found in superconductors, certain materials that conduct electricity perfectly when cooled to very low temperatures. Magnetic fields penetrate the superconducting material in the form of tiny filaments called vortices, which control the electronic and magnetic properties of the materials.
These vortices display both classical and quantum properties, which led researchers to study them for access to one of the most enigmatic phenomena of modern condensed matter physics: the Mott insulator-to-metal transition.

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Image Credit: Bilkent University UNAM

Memristors, resistors of which conductance is a function of the history of voltage applied to them, have attracted great attention in the present decade as potential components of memory and computing platforms. These long-forgotten device components were predicted over fifty years ago by Leon Chua, who described them as the fourth fundamental circuit element alongside resistors, capacitors and inductors – although the true origins of the memristor are even older than its name, as the term applies to such a broad range of electronic phenomena that the original observations of memristive behavior date over a century ago.

In the modern world, however, memristors are making a comeback: They are expected to play a major role in the development of novel computing platforms, particularly neuromorphic systems, where brain-like (cortical) computational schemes can be efficiently implemented using semiconductor technology. Recent reports on memristive switches demonstrate improvements in the uniformity and controllability of nanoionics-based memristors, though there is still a long way to go before memristors can compete with other circuit elements in forming neuromorphic systems with billions of synapses and millions of solid state neurons. On the other hand, Flash memory -another non-volatile memory technology- has reached very high densities and is readily compatible with CMOS technology, which makes it a particularly suitable model for the implementation of memristor-based applications.

In recent work at the National Nanotechnology Research Center at Bilkent University (Turkey), the Dâna group has demonstrated that junctionless flash memory cells can be operated like a memristor: The write and erase operations commonly performed through voltage pulses applied to the gate can be effected through the application of voltages through the source and drain terminals of the transistor. In fact, the equations that relate the transistor operation and charge/discharge of the floating gate show that the flash memory, when operated in this way, behaves nearly like an ideal memristor. The significance of the demonstration is that it connects the two non-volatile memory device families, the memristor and flash, and may facilitate future applications of flash memory devices in neuromorphic computing. Considering that the density of flash drives has improved to such an extent that multigigabit chips can be mass produced and have entered into virtually every cell-phone, flash technology already has the infrastructure that can enable the implemention of billions of synthetic synapses. Moreover, the flashristor mode -the new operation mode is referred to in the article- can be implemented with high uniformity and repeatability.

The group’s findings are also highlighted in the IEEE Spectrum website, which can be found at:

http://spectrum.ieee.org/tech-talk/computing/hardware/flashristors-getting-the-best-of-memristors-and-flash-memory

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Image Credit: National Institute of Standards and Technology

Two-dimensional (2D) materials* such as molybdenum-disulfide (MoS2) are attracting much attention for future electronic and photonic applications ranging from high-performance computing to flexible and pervasive sensors and optoelectronics. But in order for their promise to be realized, scientists need to understand how the performance of devices made with 2D materials is affected by different kinds of metal electrical contacts.

Researchers in the National Institute of Standards and Technology (NIST) Physical Measurement Laboratory's Semiconductor & Dimensional Metrology Division, in collaboration with researchers from George Mason University, compared silver and titanium contacts on MoS2 transistors to determine the influence of the metal–MoS2 interface. A sophisticated suite of measurements (Raman spectroscopy, scanning electron microscopy and atomic force microscopy) was used to characterize the surface morphology and the interface between MoS2 and the metals, the properties of which affect the device behavior. It was found that silver provides a much better electrical contact to MoS2 than the widely used titanium, with the silver-contact devices having 60 times higher current when the device is in the "on" state. These results are another step towards the advanced manufacture of high-value products based on 2D materials.

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Oak Ridge National Laboratory researchers used atomic force microscopy to draw nanoscale patterns in a polymerized ionic liquid. (Image Credit: ORNL)

Scientists at the U.S. Department of Energy’s Oak Ridge National Laboratory have used advanced microscopy to carve out nanoscale designs on the surface of a new class of ionic polymer materials for the first time. The study provides new evidence that atomic force microscopy, or AFM, could be used to precisely fabricate materials needed for increasingly smaller devices. Polymerized ionic liquids have potential applications in technologies such as lithium batteries, transistors and solar cells because of their high ionic conductivity and unique structure. But many aspects of the recently discovered materials are still not well understood. When ORNL researchers used an atomic force microscope to begin characterizing the properties of polymerized ionic liquid thin films, the experiment yielded some surprising results.

“We were expecting to measure ionic conductivity, and instead we found that we were forming holes on the surface,” said ORNL’s Vera Bocharova, corresponding author on the study published in Advanced Functional Materials. “Then we started to think about how this might have great applications in nanofabrication.” Nanolithography is the dominant technique used by industry for nanofabrication, but its size limitations are leading researchers to explore other methods such as AFM. “This study is part of our search for alternative methods and materials that can be used to create smaller sized objects,” Bocharova said. “For example, our technique might be interesting for the miniaturization of semiconductor technology.”

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Chuck Black of the Center for Functional Nanomaterials displays a nanotextured square of silicon on top of an ordinary silicon wafer. The nanotextured surface is completely antireflective and could boost the production of solar energy from silicon solar cells. (Image Credit: BNL)

Reducing the amount of sunlight that bounces off the surface of solar cells helps maximize the conversion of the sun's rays to electricity, so manufacturers use coatings to cut down on reflections. Now scientists at the U.S. Department of Energy's Brookhaven National Laboratory show that etching a nanoscale texture onto the silicon material itself creates an antireflective surface that works as well as state-of-the-art thin-film multilayer coatings. Their method has potential for streamlining silicon solar cell production and reducing manufacturing costs. The approach may find additional applications in reducing glare from windows, providing radar camouflage for military equipment, and increasing the brightness of light-emitting diodes. "For antireflection applications, the idea is to prevent light or radio waves from bouncing at interfaces between materials," said physicist Charles Black, who led the research at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility.

Preventing reflections requires controlling an abrupt change in "refractive index," a property that affects how waves such as light propagate through a material. This occurs at the interface where two materials with very different refractive indices meet, for example at the interface between air and silicon. Adding a coating with an intermediate refractive index at the interface eases the transition between materials and reduces the reflection, Black explained. "The issue with using such coatings for solar cells," he said, "is that we'd prefer to fully capture every color of the light spectrum within the device, and we'd like to capture the light irrespective of the direction it comes from. But each color of light couples best with a different antireflection coating, and each coating is optimized for light coming from a particular direction. So you deal with these issues by using multiple antireflection layers. We were interested in looking for a better way." For inspiration, the scientists turned to a well-known example of an antireflective surface in nature, the eyes of common moths. The surfaces of their compound eyes have textured patterns made of many tiny "posts," each smaller than the wavelengths of light. This textured surface improves moths' nighttime vision, and also prevents the "deer in the headlights" reflecting glow that might allow predators to detect them.

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(Image Credit: University of Oregon)

Scientists, including University of Oregon chemist Geraldine Richmond, have tapped oil and water to create scaffolds of self-assembling, synthetic proteins called peptoid nanosheets that mimic complex biological mechanisms and processes. The accomplishment is expected to fuel an alternative design of the two-dimensional peptoid nanosheets that can be used in a broad range of applications. Among them could be improved chemical sensors and separators, and safer, more effective drug-delivery vehicles. Study co-author Ronald Zuckermann of the Molecular Foundry at Lawrence Berkeley National Laboratory (LBNL) first developed these ultra-thin nanosheets in 2010 using an air-and-water combination.

"We often think of oil on water as something that is environmentally bad when, in fact, my group over the past 20 years has been studying the unique properties of the junction between water and oil as an interesting place for molecules to assemble in unique ways — including for soaps and oil dispersants," said Richmond, who holds a UO presidential chair. "This study shows it is also a unique platform for making nanosheets." To create the new version of the nanosheets, the research team used vibrational sum frequency spectroscopy to probe the molecular interactions between the peptoids as they assemble at the oil-water interface. The work showed that peptoid polymers adsorbed to the interface are highly ordered in a way that is influenced by interactions between neighboring molecules.

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Pieces of Kimsooja's "Needle Woman" artwork during fabrication in Shanghai show the polymer film developed by Cornell researchers. (Image Credit: Cornell University/Jaeho Chong)

For her newest work, Korean artist Kimsooja wanted to explore a “shape and perspective that reveals the invisible as visible, physical as immaterial, and vice versa.” As artist-in-residence for the Cornell Council for the Arts’ (CCA) 2014 Biennial, she has realized that objective with “A Needle Woman: Galaxy was a Memory, Earth is a Souvenir,” one of several installations on campus for the semesterlong biennial, “Intimate Cosmologies: The Aesthetics of Scale in an Age of Nanotechnology.” The biennial, which runs through December 21, is a deep survey of artistic and scientific exploration, framing changes in 21st-century culture, art practice and nanoscale technology through collaborative research-based projects by faculty and students and guest artists. Kimsooja’s 46-foot-tall structure features an iridescent polymer film developed at Cornell, reflecting light with structural colors similar to those in a butterfly’s wings. Creating it involved some diligent problem-solving by materials scientists in the lab of Uli Wiesner, the Spencer T. Olin Professor of Engineering.

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