The Next FET...

Source: Modeling Carbon Nanotube FET Physics in COMSOL Multiphysics®

Topics: Applied Physics, Carbon Nanotubes, Field Effect Transistors, Nanotechnology

Silicon field-effect transistors (FETs) were developed in the late 1950s as a scaled-down, energy-efficient substitute for bipolar junction transistors. They paved the way for the high-density integrated circuits that today underlie most electronics (see the article by Alan Fowler, Physics Today, October 1993, page 59). With their lower gate voltages, carbon nanotube FETs could surpass silicon FET energy efficiency by nearly a factor of 10. In 2013 Subhasish Mitra, Max Shulaker (then at Stanford University), and coworkers made the first CNFET microprocessor; it comprised 178 transistors and could run a single operation.

Variability caused by the production process has made moving beyond that proof-of-concept computer challenging. Gage Hills, Christian Lau, and coworkers in Shulaker’s group at MIT have now overcome that hurdle with a protocol for wafer-scale CNFET microprocessor production. Their technique is also compatible with existing CMOS infrastructure, which lowers the bar for future commercial implementation.

To remove carbon nanotube aggregates—a common contaminant from CNT deposition on silicon wafers—the researchers spin-coated a layer of adhesive polymer over the device and then removed the aggregates using ultrasonic vibrations. In previous attempts, sonication damaged the nonaggregated CNTs. Using the photoresist binds them to the wafer, which preserves their function while removing more than 99% of the aggregates.

Production of carbon nanotube microprocessors gets scaled up
Christine Middleton, Physics Today

Darkest Black...

Image Source: CNET: Sci-Tech

Topics: Carbon Nanotubes, Materials Science, Nanotechnology, Optics

The Science of Vantablack

The name Vantablack® stands for Vertically Aligned Nanotube Array black.

Vantablack is a free-space coating consisting of a 'forest' of aligned and equally spaced, high aspect-ratio carbon nanotubes (CNTs).

The CNT array is patterned and spaced to allow photons to enter. Most of the light, or radiation arriving at the surface enters the space between the CNTs, and is repeatedly reflected between tubes until it is absorbed and converted to heat. This heat (largely undetectable in most applications) is conducted to the substrate and dissipated. The Vantablack array is very largely free-space; the volume of CNTs only makes up about 0.05% of the coating. Consequently, only a minuscule proportion of the incident radiation is able to hit the tip of a CNT, explaining why such a small amount is reflected back to the observer.

Vantablack's exceptional properties

Ultra low reflectance - Vantablack absorbs 99.965% of light (750nm wavelength)

UV, Visible and IR absorption - Absorption works from UV (200-350 nm wavelength), through the visible (350-700nm) and into the far infrared (>16 microns) spectrum, with no spectral features.

Very high front to back thermal conduction - excellent for Black Body calibration sources

Super hydrophobic - Unlike other black coatings, water has no impact on the optical properties

Very high thermal shock resistance - Repeatedly plunging a Vantablack coated substrate into liquid Nitrogen at -196°C and then transferring to a 300°C hot plate in air does not affect its properties.

Resistant to extreme shock and vibration - Independently tested, Vantablack has been subjected to severe shocks and vibration simulating launch and staging.

Information Source: Surrey Nanosystems

Carbon Nanotube FET...

Figure 1.
A three-dimensional integrated circuit, made possible with carbon nanotubes (CNTs). The circuit senses and classifies ambient gases using a multilayered stack of devices that are connected by platinum wires known as interlayer vias. In the top layer, roughly 1 million CNT field-effect transistors (FETs) register a change in electrical resistance when the gas molecules adsorb on a CNT. The second layer hosts memory cells that read and store the signals created by the FETs just above them. The third layer contains another million FETs that process the sensor data and implement a machine-learning algorithm to identify the type of gas picked up. Conventional silicon CMOS circuitry on the bottom acts as an interface to external devices. (Adapted from ref. 2.)

Topics: Carbon Nanotubes, Computer Engineering, Nanotechnology, Quantum Mechanics

In 2013 graduate student Max Shulaker, his adviser Subhasish Mitra, Philip Wong, and their Stanford University colleagues built the first computer made entirely of carbon nanotube (CNT) field-effect transistors (FETs). ¹ The achievement was eagerly anticipated. Even before their first incorporation into FETs in 1998, CNTs had been touted as a superior substitute for the silicon channel that shuttles current between the traditional FET’s source and drain electrodes.

The intrinsic thinness of single-wall CNTs—essentially graphene sheets rolled into hollow cylinders a nanometer wide—enables superb control over power dissipation in the transistor’s off state and allows the transistor to switch off and on with much lower energy consumption than is possible with any other material. Moreover, thanks to that one-dimensionality, which suppresses scattering, charge carriers in CNTs have a much higher velocity for a given electric field than in Si. (See the article by Phaedon Avouris, Physics Today, January 2009, page 34.)

The 2013 computer was modest: It contained fewer than 200 FETs, ran at a clock speed of just 1 kHz, and implemented a single instruction. Nonetheless, the instruction was a conditional statement that qualified the computer as “Turing complete,” able to make any calculation given enough memory and time. The achievement also reassured Shulaker, now a professor at MIT, and his Stanford colleagues that CNTs could form the foundation for a much more complex system.

The researchers have now built a prototype system that embodies a vision of a transformative computer architecture—one in which computing, data storage, and input and output technologies are each fabricated into two-dimensional layers that are built up into a 3D integrated circuit.² Shown schematically in figure 1, the circuit consists of more than 2 million CNT FETs and more than 1 million memory cells. The components are divided among three layers—stacked on the same chip atop a layer of Si CMOS circuitry and interconnected by a forest of fine platinum wires.

The carbon nanotube integrated circuit goes three-dimensional
R. Mark Wilson, Physics Today

Imaging Neurotransmitters...

The nanosensor array is composed of single-walled carbon nanotubes (SWCNTs) deposited on a microscope slide. These nanotubes fluoresce in the near infrared when excited with laser light and are wrapped in single-stranded DNA to make them fluoresce brightly in the presence of dopamine. Courtesy: D Salem

Topics: Carbon Nanotubes, Biology, Nanotechnology

Chemical signalling between biological cells is the very essence of life, but it is difficult to measure such signals using existing techniques – such as those that rely on microfabricated electrodes, for example. A team of researchers from the Massachusetts Institute of Technology (MIT) have now succeeded in imaging how the neurotransmitter dopamine is released from a single cell using an array of 20,000 individually addressable sensors. The spatiotemporal resolution of the new technique is several orders of magnitude larger than that of previously reported electrode-based approaches.

Cells communicate with each other using waves of chemical concentrations that change in both direction and time. However, unlike electrical potentials, measuring this chemical signalling between cells and within cellular networks is more difficult – and especially at the spatial resolutions required to find out exactly from where on a cell chemicals are released.

Michael Strano and colleagues have now taken an important step forward to overcoming this problem. The researchers have developed fluorescent nanosensors based on single carbon nanotubes that can be placed under and around neuroprogenitor cells and image how the neurotransmitter dopamine is released from these cells. Thanks to their small size, as many as 20,000 sensors can be placed around an individual cell.

SWCNTs fluoresce brightly in the presence of dopamine

“The nanosensor array is composed of single-walled carbon nanotubes (SWCNTs) deposited on a microscope slide,” explains team member Daniel Salem. “These nanotubes fluoresce in the near-infrared (nIR) part of the electromagnetic spectrum when they are excited with laser light and we wrap them in single-stranded DNA to make them fluoresce brightly in the presence of dopamine.

“By imaging the surface beneath a cell with these sensors and making a movie of the nIR fluorescence, we are able to observe turn-on responses of individual pixels and correlate these with dopamine release from the cell.”

SWCNTs are versatile building blocks for biosensors, he says, and can detect down to the single-molecule level. The researchers chose to study dopamine in their work because it plays a central role in reward control and learning in humans.

Nanotechweb: Nanotube array images neurotransmitter signals, Belle Dumé

Single File...

Illustration of a sealed and empty single-walled carbon nanotube (top) and a nanotube filled with water.
(Courtesy: Xuedan Ma et al/Phys. Rev. Lett.)

Topics: Biology, Cancer, Carbon Nanotubes, Nanotechnology, Research

The optical properties of single-walled carbon nanotubes (SWCNTs) change when the tiny structures are filled with water. That is the conclusion of scientists in Belgium and the US, who attribute the change to a "quasi-phase transition" that occurs in the water – although the exact nature of the transition is unknown. The research points to a new technique for studying confined water molecules – which is crucial to various branches of science, but it is surprisingly difficult to do. The study could lead to better ways of delivering drugs in the body and even boost our understanding of quantum mechanics.

SWCNTs are hollow hair-like structures with walls that are one atom thick. Normally they are closed at both ends, but sometimes the ends can be open and Sofie Cambré of the University of Antwerp in Belgium and colleagues have previously shown that open SWCNTs rapidly fill with other molecules and hold on to them. Why this occurs is not well understood, but Cambré says "it seems the energy of a molecule inside a SWCNTs is much lower than when you have them separated."

SWCNTs are naturally fluorescent, and the colour of the fluorescent light shifts if the nanotube is filled. "You need dedicated equipment to really see these very small shifts", Cambré says. However, by measuring the shifts, researchers can potentially gain useful insights into the behaviour of confined molecules.

Physics World:
Quasi-phase transition spotted in water-filled carbon nanotubes, Tim Wogan

Nanomechanics...

Molecular geometry of plastic deformation. Subplot (a): snapshots of the deformation mechanisms, pure CF, for increasing strain. Fibrillar yield is characterized by intermolecular slip (see the circles highlighting a local area of repeated molecular slip). Slip leads to the formation of regions with lower material density. Subplot (b): snapshots of the deformation mechanisms, mineralized collagen fibrils, for increasing strain. Slip initiates at the interface between hydroxyapatite particles and tropocollagen molecules. Slip reduces the density, leading to the formation of nanoscale voids. Courtesy of Nanotechnology

Topics: Biology, Materials Science, Carbon Nanotubes, Nanotechnology

Nanostructures, such as carbon nanotubes, are often added to polymers and composites to enhance their strength. The extreme mechanical properties of carbon nanotubes suggest an obvious rationale behind this approach. However, as Markus Buehler and Isabelle Su at Massachusetts Institute of Technology in the US highlight in their recent topical review, the behaviour that renders nanomaterials soft or strong can be far from trivial, often involving interactions on a range of scales from macrostructures to nanostructures and – in the case of biostructures – the amino acids and proteins they are built from.

Bone is a classic example of excellent natural material engineering. It primarily consists of tropocollagen fibrils – which would be too soft to support the weight of the skeleton under its daily loads – and hydroxyapatite, a stiff but fragile material prone to fracture. However, the alliance of these two imperfect candidates is an extremely tough, lightweight and robust material.

Based on a simple molecular model of mineralized collagen fibrils, Buehler showed that, as might be expected, the stiffness of mineralized fibrils lies somewhere between the two extremes of the component materials, with as more recent studies reveal, the mineral components bearing up to four times the stress of the collagen fibrils. However, in addition his 2007 study pointed out that the mineralization increases the energy dissipation during deformation. As he explains in his report, “The fibrillar toughening mechanism increases the resistance to fracture by forming large local yield regions around crack-like defects, a mechanism that protects the integrity of the entire structure by allowing for localized failure.”

Nanotechweb:
Nanomechanics – the whole is more than the sum of its parts, Anna Demming

Simpler, Faster, Cheaper...

To prevent cores of single-wall carbon nanotubes from filling with water or other detrimental substances, the NIST researchers advise intentionally prefilling them with a desired chemical of known properties. Taking this step before separating and dispersing the materials, usually done in water, yields a consistently uniform collection of nanotubes, especially important for optical applications.
Credit: Fagan/NIST
View hi-resolution image

Topics: Carbon Nanotubes, Electrical Engineering, Nanotechnology, Semiconductor Technology

Just as many of us might be resigned to clogged salt shakers or rush-hour traffic, those working to exploit the special properties of carbon nanotubes have typically shrugged their shoulders when these tiniest of cylinders fill with water during processing. But for nanotube practitioners who have reached their Popeye threshold and “can’t stands no more,” the National Institute of Standards and Technology (NIST) has devised a cheap, quick and effective strategy that reliably enhances the quality and consistency of the materials—important for using them effectively in applications such as new computing technologies.

To prevent filling of the cores of single-wall carbon nanotubes with water or other detrimental substances, the NIST researchers advise intentionally prefilling them with a desired chemical of known properties. Taking this step before separating and dispersing the materials, usually done in water, yields a consistently uniform collection of nanotubes. In quantity and quality, the results are superior to water-filled nanotubes, especially for optical applications such as sensors and photodetectors.

The approach opens a straightforward route for engineering the properties of single-wall carbon nanotubes—rolled up sheets of carbon atoms arranged like chicken wire or honey combs—with improved or new properties.

“This approach is so easy, inexpensive and broadly useful that I can’t think of a reason not to use it,” said NIST chemical engineer Jeffrey Fagan.

NIST:
Simpler, Faster and Cheaper: A Full-filling Approach to Making Carbon Nanotubes of Consistent Quality, Mark Bello

Nano Oasis...

Researchers have accidentally created nanorods that can absorb water at low humidity and expel it as the humidity increases.

Topics: Carbon Nanotubes, Materials Science, Metamaterials, Nanotechnology

Learning from your mistakes is a key life lesson, and it's one that researchers at Pacific Northwest National Laboratory (PNNL) can attest to. After unintentionally creating carbon-rich nanorods, the team realized its accidental invention behaves weirdly with water, demonstrating a 20-year old theory and potentially paving the way to low-energy water harvesting systems and sweat-removing fabrics.

The researchers note that ordinarily materials will absorb more water as the humidity in the air around them increases. But between 50 and 80 percent relative humidity, these nanorods will actually do the opposite and expel water, a behavior they say is not shared by any other material. Below that range, they behave as normal, so the process is reversible by lowering the humidity again.

"Our unusual material behaves a bit like a sponge; it wrings itself out halfway before it's fully saturated with water," says David Lao, PNNL research associate and creator of the material.

These nanorods were created by mistake while trying to fabricate magnetic nanowires, and the researchers decided to give the accidents a closer look. On examining them with a vapor analysis instrument, Satish Nune, one of the authors of the research paper, noticed that the structures were actually losing weight as the humidity increased.

Gizmag:
Scientists accidentally create nanorods that harvest water from the air, Michael Irving

STEP...

The Solar Thermal Electrochemical Process (STEP) converts atmospheric carbon dioxide into carbon nanotubes that can be used in advanced batteries. Credit: Julie Turner, Vanderbilt University

Topics: Alternative Energy, Carbon Nanotubes, Climate Change, Global Warming, Green Energy, Green Tech, Greenhouse Gases, Nanotechnology

An interdisciplinary team of scientists has worked out a way to make electric vehicles that are not only carbon neutral, but carbon negative, capable of actually reducing the amount of atmospheric carbon dioxide as they operate.

They have done so by demonstrating how the graphite electrodes used in the lithium-ion batteries that power electric automobiles can be replaced with carbon material recovered from the atmosphere.

The recipe for converting carbon dioxide gas into batteries is described in the paper titled "Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes" published in the Mar. 2 issue of the journal ACS Central Science.

The unusual pairing of carbon dioxide conversion and advanced battery technology is the result of a collaboration between the laboratory of Assistant Professor of Mechanical Engineering Cary Pint at Vanderbilt University and Professor of Chemistry Stuart Licht at George Washington University.

Phys.org: Converting atmospheric carbon dioxide into batteries

Bubble Pen Lithography...

Schematic illustration of the pattern-writing process using an optically controlled microbubble on a plasmonic substrate and the logo of “UT-AUSTIN” written with 60 nm polystyrene beads. Courtesy: M Yogeesh

Topics: Biology, Carbon Nanotubes, Medical Physics, Nanotechnology, Photonics, Semiconductor Technology

A new “bubble-pen” lithography technique can be used to pattern colloidal and biological particles on solid-state substrates according to researchers at the University of Texas at Austin. The technique, which works by using laser-controlled microbubbles to create the patterns, will find a wide range of applications in microelectronics, nanophotonics and nanomedicine.

Photolithography is one of the main techniques available today to make micro- and nano-scale components for semiconductor devices. However, the problem is that these methods have inherent disadvantages. “Far-field" optical lithography, for example, is limited by the so-called diffraction limit of light, which means that it is extremely difficult to create features smaller than several hundred nanometres across. Techniques based on "near-field" scanning optical microscopy can overcome the diffraction limit by bringing the light source very near to the surface, but they are low-throughput and can only scan small areas at a time. Electron-beam lithography, although able to produce much smaller features, is also limited by the choice of working materials and substrates that can survive exposure to an electron beam.

The new bubble-pen lithography technique invented by Yuebing Zheng's team in collaboration with Deji Akinwande's and Andrew Dunn's groups in Texas uses a single low-power laser beam to generate a microbubble at the interface of a colloidal suspension of nanoparticles and a plasmonic substrate containing a network of metallic nanoparticles that interact strongly with light via localized surface plasmons (collective oscillations of electrons on a metal's surface). These metal particles act as efficient optical nanoantennas and can focus light to wavelengths dramatically below the diffraction limit. The microbubble produced captures and immobilizes the colloidal particles on the substrate and by directing the laser beam to move the bubble, the researchers can create different patterns from the colloidal particles with varying sizes and architectures.

Nanotechweb: Bubble-pen lithography patterns nanodevices, Belle Dumé

Seeing The Light...

Drawing illustrates how tiny changes in wavy images scattered from lines in a grid-like array can be reconstructed when paired with advanced optical and computational techniques. Lines are 15 nanometers wide, 30 times smaller than the wavelength used to “see” them. The pattern depicts estimated uncertainties in the experimental data. Coloring corresponds to the magnitude of the variance for specific data points.

Topics: Carbon Nanotubes, Consumer Electronics, Nanotechnology, Semiconductor Technology

National Institute of Standards and Technology (NIST) researchers are seeing the light, but in an altogether different way. And how they are doing it just might be the semiconductor industry's ticket for extending its use of optical microscopes to measure computer chip features that are approaching 10 nanometers, tiny fractions of the wavelength of light.

Using a novel microscope that combines standard through-the-lens viewing with a technique called scatterfield imaging, the NIST team accurately measured patterned features on a silicon wafer that were 30 times smaller than the wavelength of light (450 nanometers) used to examine them. They report* that measurements of the etched lines—as thin as 16 nanometers wide—on the SEMATECH-fabricated wafer were accurate to one nanometer. With the technique, they spotted variations in feature dimensions amounting to differences of a few atoms.

"Historically, we would ignore this scattered light because it did not yield sufficient resolution," explains Richard Silver, the physicist who initiated NIST's scatterfield imaging effort. "Now we know it contains helpful information that provides signatures telling us something about where the light came from."

With scatterfield imaging, Silver and colleagues methodically illuminate a sample with polarized light from different angles. From this collection of scattered light—nothing more than a sea of wiggly lines to the untrained eye—the NIST team can extract characteristics of the bounced lightwaves that, together, reveal the geometry of features on the specimen.

NIST: Measuring Nanoscale Features with Fractions of Light, Mark Bello

Small Solutions For Big Problems...

Image source: National Physical Laboratory

Topics: Carbon Nanotubes, Diversity, Diversity in Science, Engineering Physics, Materials Science, Nanotechnology, Semiconductor Technology, Women in Science

Stephanie Moroz and I share the same background in Engineering Physics and both in the same industry at the moment (she has extensive experience in other areas as well, and I'm not a CEO). She gives an excellent primer presentation at TEDx:

What is nanotechnology? Stephanie Moroz explores some of the ways that designing materials at an incredibly small scale can address global challenges in fields such as energy, medicine and electronics.

Stephanie Moroz is the CEO of Nano-Nouvelle, a Sunshine Coast company developing high-performance battery electrodes. Her international career has been dedicated to commercializing new technologies, particularly in the areas of energy efficiency and nanomaterials.

Stephanie is a truly global citizen. With her education in engineering physics, she has worked in Canada and then Germany where she led the integration of hydrogen fuel cells into the Mercedes F-CELL vehicle. From there she moved to France, developing systems to reduce the pollution generated by conventional vehicles. Finally, she was lured to Australia by opportunities in nanotechnology: first in solid-state hydrogen storage and now innovative battery materials at Nano-Nouvelle.

This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at http://ted.com/tedx

Graphene Ice Sandwich...

Square ice between two graphene sheets as seen in a transmission electron microscope. High-contrast dark spots are oxygen atoms that indicate positions of water molecules. Hydrogen atoms yield too little contrast to be resolved even by the state-of-the-art TEM. The top right inset shows a magnified image of a small area in the centre of the ice crystal. Credit: University of Ulm, Germany

Topics: Carbon Nanotubes, Graphene, Nanotechnology, Nanostructures

Researchers in the UK, Germany and China say they have observed a new type of frozen water in the form of square ice sandwiched between sheets of graphene. The ice films, which are less than 1 nm thick, have a completely different symmetry to that of normal ice – which has a hexagonal structure. This ice should also exist inside certain other types of nanostructures, such as carbon nanotubes, and could help explain why water moves unusually in these materials – a result that could have implications for developing more efficient filtration, desalination and distillation technologies.

"The new phase of ice forms at room temperature, well above the 'normal' freezing temperature of water," explain team leaders Irina Grigorieva and Andre Geim of the University of Manchester in the UK. "Apart from finding this new phase – not something that happens every day – our result will allow us to better understand the counterintuitive behaviour of water inside nanochannels, such as ultrafast permeation though graphene oxide membranes."

Nanotech Web: Square ice forms in graphene sandwich, Belle Dumé, contributing editor at nanotechweb.org

On The Dot...

Physicists in Finland and Russia have shown how graphene quantum dots can be used to split Cooper pairs. (Courtesy: Shutterstock/Mopic)

Topics: Cooper Pairs, Graphene, Modern Physics, Superconductivity, Quantum Computers, Quantum Mechanics

Superconducting "Cooper pairs" of electrons have been split to create entangled pairs of electrons in a new device built by physicists in Finland and Russia. The device employs two quantum dots made of graphene. Although other types of quantum dots have been used for this purpose, the latest research suggests that graphene quantum dots should deliver long-lived entangled electron pairs that could be used in quantum computers.

Entanglement is a quantum-mechanical phenomenon in which properties of fundamental particles are correlated so that making a measurement on one particle can instantaneously affect another particle – even across very large distances. In principle, a quantum computer can use this connectedness to perform certain calculations much faster than a conventional computer. Although practical quantum computers do not exist today, some potential designs involve using the intrinsic angular momenta, or "spin", of electrons as quantum bits (qubits) of information that can be entangled.

Superconductors provide a ready source of entangled electrons because the Cooper pairs that allow these materials to conduct electricity with little or no resistance are in fact entangled pairs of electrons with opposite spin. Splitting the pairs while preserving the electrons' entanglement can be done simply by connecting ordinary metal wires to either end of the superconductor. If the set-up is just right, each wire will carry away one electron from a pair. However, it is more often the case that both electrons will end up going down the same wire.

Physics World: Graphene quantum dots split Cooper pairs, Edwin Cartlidge

Dr. Nadya Mason...

Mayer                                            Mason

Topics: Carbon Nanotubes, Diversity in Science, Nanotechnology, Women in Science

Dr. Nadya Mason

University of Illinois, repost: 2012 Maria Goeppert Mayer Prize recipient

Citation:

"For innovative experiments that elucidate the electronic interactions and correlations in low-dimensional systems, in particular the use of local gates and tunnel probes to control and measure the electronic states in carbon nanotubes and graphene."

 

Additional note: The first photograph of a Maria Goeppert Mayor Prize recipient seems to be in 1996 with Dr. Majorie Ann Olmstead, most likely made a part of the site as society got comfortable with the Internet, advances in tools and what could be posted. The prize has been awarded by APS since 1986: "To recognize and enhance outstanding achievement by a woman physicist in the early years of her career, and to provide opportunities for her to present these achievements to others through public lectures in the spirit of Maria Goeppert Mayer." Dr. Mason seems to be - at first brush of the site - the first African American woman awarded this honor.

I attended her talk at the NSBP conference in Austin, Texas. Nobel Prize next, Dr. Mason!

NobelPrize.org: Maria Goeppert Mayer Biography

Silicene Transistor...

Image: University of Texas at Austin, Source: IEEE link below

Topics: Graphene, Nanotechnology, Semiconductor Technology, STEM

TECHNOLOGY REVIEW: An exotic but tricky-to-use new form of silicon is being eyed as a way to build much faster computer chips. And now, those who see its potential can claim a minor victory by making the first transistors out of the stuff.

The material in question, called silicene, comes in layers of silicon just one-atom thick. This structure gives the material fantastic electrical properties, but it also means it’s devilishly tricky to produce and work with. Even testing its basic properties in the lab has proved difficult.

Now Deji Akinwande, a computer engineer at the University of Texas at Austin, has figured out how to work with the stubborn material well enough to make the first silicene transistors. His first-of-their-kind devices are described today in the journal Nature Nanotechnology, and they live up to silicene’s promise by switching with extraordinary speed.

Another atom-thick material, graphene, which is made from carbon, has gained attention in recent years for its own electrical properties. The appeal of silicene, says Akinwande, is that it’s made from the stuff Silicon Valley was built on. In theory, it should be easier for chipmakers to work with than some new material. “If we can get good properties out of it, it can be translated immediately by the semiconductor industry,” Akinwande says.

Deji received a B.S/M.S. combined degree in Electrical Engineering and Applied Physics from Case Western Reserve University, Cleveland, Ohio. His master’s research involved the development and characterization of evanescent microwave probes for non-destructive imaging of materials. Afterwards, he gained experience designing and testing a variety of analog circuits from MHz to 110 GHz for network analyzer and signal generator instruments at Agilent Technologies in northern California.

He subsequently worked at XtremeSpectrum, Freescale and Motorola on the modeling, design and testing of the first commercial 100 Mb/s ultra-wideband receiver chip.

He received the Ph.D. degree from Stanford University in December 2009. His thesis focused on the physics, chemistry, materials and electronic properties of carbon materials. He has published widely on carbon nanomaterials in a variety of disciplines including physics, chemistry, materials, and electrical engineering journals.

Professor Akinwande joined UT Austin starting from January 2010, and he is a member of IEEE, APS, ACS, and MRS societies.

Extreme Tech:
Silicene could help create create an alternative to graphene with many of its benefits, Joel Hruska
Nature: Graphene's cousin silicene makes transistor debut, Mark Peplow
Spectrum IEEE: Transistor Made From Silicene for the First Time,
Dexter Johnston

International Year of Light...

The International Year of Light and Light-based Technologies will see hundreds of events around the world celebrating the science and applications of light.

Physicists around the world are gearing up for the International Year of Light and Light-based Technologies (IYL), which kicks off later this month at an official opening ceremony at the headquarters of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in Paris. Some 1500 delegates are set to converge on the French capital for the event, which runs from 19 to 20 January, and will include representatives from the UN and UNESCO as well as the Nobel laureates Zhores Alferov, Steven Chu, Serge Haroche and William Phillips. Designed to highlight how light and light-based technologies touch every aspect of our lives, the IYL will involve more than 100 partners from 85 countries – including the Institute of Physics (IOP), which publishes Physics World.

The UN has declared "international years" since 1959 to draw attention to topics deemed to be of worldwide importance. In recent years, there have been a number of successful science-based themes, including physics (2005), astronomy (2009), chemistry (2011) and crystallography (2014), with the idea for a celebration of light having been initiated by the European Physical Society (EPS) in 2009.

It is light and its careful, focused exposure to finer details that has allowed us to shrink feature sizes and thus technologies in line with Moore's Law. Beyond light, we're looking at nanomanufacturing techniques using e-beam (electrons); nanoimprinting, nanoscratching and using AFM (atomic force microscope) and STM (scanning tunneling microscopy) for finer control still (ref: Physics Today, "Top-down Nanomanufacturing," Matthias Imboden and David Bishop, page 47). This post accompanies Monday's "Fab on a Chip" post. What we do in this industry is not trivial, but it is learn-able, doable and quite rewarding with the right dedication and discipline.

Physics World: Physicists get set for UNESCO's Year of Light

Physics 2014...

First Realistic Virtual Universe (see 5 below)

In May cosmologists took the place on the pedestal by releasing the first simulated universe of such a large scale: it simulated 13 billion years of cosmic evolution in a cube with 350 million light year long sides. “Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously,” said the lead author Mark Vogelsberger.

1. Deepest Image of a Galaxy Cluster (January)
2. NASA Releases First Images Taken by the Curiosity Rover ( February)
3. The Discovery of Gravitational Waves (March), though there's some recent data that cast doubt.
4. NASA’s Exoplanet Discoveries (April)
5. The First Realistic Virtual Universe (May)
6. Hybrid Carbon Nanotube Circuits (June)
7. OCO-2 Launched (July) The OCO-2 will study carbon dioxide concentrations and distributions in the atmosphere.
8. Field Medals and IBM’s Neuromorphic Computer Chip (August)
9. Water Vapour Found on an Exoplanet + India’s First Probe to Mars (September)
10. Nobel Prizes (October), the winners were Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, who were responsible for the development of the efficient blue light diodes.
11. Landing on a Comet (November), the first landing on the surface of a comet performed by the Rosetta spacecraft equipped with Philae landing module.
12. Planck 2014 Results (December)
The newest data suggests that the universe is 13.8 billion years old and is composed of 4.9 percent atomic matter, 26.6 percent dark matter and 68.5 percent dark energy.

Physics Database: Top Physics News of 2014

Nanobuds...

A nanobud consists of a tube of carbon atoms with a bud-like appendage.

Transparent films containing carbon nanobuds—molecular tubes of carbon with ball-like appendages—could turn just about any surface, regardless of its shape, into a touch sensor.

The films were developed by a Finnish startup, Canatu, and could be used to add touch controls to curved automobile consoles and dashboards, for example. The films are rugged and can be repeatedly bent around something as thin as the cord for your earbuds, so they could be handy for adding buttons to flexible devices.

Touch screens are usually made by overlaying a display screen with a transparent sheet of indium tin oxide. This material is brittle, however, and can’t be used on anything other than a flat surface. Individual carbon nanotubes have long been seen as a promising alternative because they conduct electricity so well. But carbon nanotubes have performed badly in touch screens due to poor electrical connections between different nanotubes. Carbon nanobuds are better because the ball-like appendages are particularly good at emitting electrons, which improves those electrical connections.

MIT Technology Review:
“Nanobuds” Could Turn Almost Any Surface Into a Touch Sensor, Kevin Bullis

Dumbbells and Detection Techniques...

Figure 1: Nano-objects with varying curvatures, Nature

ARGONNE, Ill. – Like snowflakes, nanoparticles come in a wide variety of shapes and sizes. The geometry of a nanoparticle is often as influential as its chemical makeup in determining how it behaves, from its catalytic properties to its potential as a semiconductor component. 

Thanks to a new study from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, researchers are closer to understanding the process by which nanoparticles made of more than one material – called heterostructured nanoparticles – form. This process, known as heterogeneous nucleation, is the same mechanism by which beads of condensation form on a windowpane.

Heterostructured nanoparticles can be used as catalysts and in advanced energy conversion and storage systems. Typically, these nanoparticles are created from tiny “seeds” of one material, on top of which another material is grown. In this study, the Argonne researchers noticed that the differences in the atomic arrangements of the two materials have a big impact on the shape of the resulting nanoparticle. [1]

ARGONNE, Ill. ― A team of researchers from the U.S. Department of Energy's Argonne National Laboratory and Ohio University have devised a powerful technique that simultaneously resolves the chemical characterization and topography of nanoscale materials down to the height of a single atom.

The technique combines synchrotron X-rays (SX) and scanning tunneling microscopy (STM). In experiments, the researchers used SX as a probe and a nanofabricated smart tip of a STM as a detector.

Using this technique, researchers detected the chemical fingerprint of individual nickel clusters on a copper surface at a two-nanometer (nm) lateral resolution, and at the ultimate single atom height sensitivity. By varying the photon energy, the researchers used the difference in photoabsorption cross sections for nickel and the copper substrate to chemically image a single-nickel nanocluster - thus opening the door to new opportunities for chemical imaging of nanoscale materials. Until now, a spatial limit of about only 10-nm was attainable, and the researchers would simultaneously sample a large sample area. The researchers have improved the spatial resolution to 2 nm. [2]

Argonne National Laboratories:
1. Atomic 'mismatch' creates nano 'dumbbells', Jared Sagoff
2. Powerful new technique simultaneously determines nanomaterials' chemical makeup, topography, Angela Hardin