Posts belonging to Category electronics



After Graphene, New 2D Materials To Play With

Dozens of new two-dimensional materials similar to graphene are now available, thanks to research from University of Manchester scientists. These 2D crystals are capable of delivering designer materials with revolutionary new properties. The problem has been that the vast majority of these atomically thin 2D crystals are unstable in air, so react and decompose before their properties can be determined and their potential applications investigated.  By protecting the new reactive crystals with more stable 2D materials, such as , via computer control in a specially designed inert gas chamber environments, these materials can be successfully isolated to a single atomic layer for the first time.
2D materials

The team created devices to stablise 2D materials

Combining a range of 2D materials in thin stacks give scientists the opportunity to control the properties of the materials, which can allow ‘materials-to-order’ to meet the demands of industry.  High-frequency electronics for satellite communications, and light weight batteries for mobile energy storage are just two of the application areas that could benefit from this research. The breakthrough could allow for many more atomically thin materials to be studied separately as well as serve as building blocks for multilayer devices with such tailored properties.

The team, led by Dr Roman Gorbachev, used their unique fabrication method on two particular two-dimensional crystals that have generated intense scientific interest in the past 12 months but are unstable in air: black phosphorus and niobium diselenide. The technique the team have pioneered allows the unique characteristics and excellent electronic properties of these air-sensitive 2D crystals to be revealed for the first time.

The isolation of graphene in 2004 by a University of Manchester team lead by Sir Andre Geim and Sir Kostya Novoselov led to the discovery of a range of 2D materials, each with specific properties and qualities. Dr Gorbachev said: “This is an important breakthrough in the area of 2D materials research, as it allows us to dramatically increase the variety of materials that we can experiment with using our expanding 2D crystal toolbox”. The more materials we have to play with, the greater potential there is for creating applications that could revolutionise the way we live.” Sir Andre Geim added.

Writing in NanoLetters, the University of Manchester team demonstrate how tailored fabrication methods can make these previously inaccessible materials useful.

Source: http://www.manchester.ac.uk/

Black Phosphorus Instead Of Silicon

Silicon Valley in Northern California got its nickname from the multitude of computer chip manufacturers that sprung up in the surrounding area in the 1980’s.  Despite its ubiquity as a chip building material, silicon may be facing some competition from a new version of an old substance.

Researchers working at the Institute for Basic Science (IBS) Center for Integrated Nanostructure Physics at Sungkyunkwan University (SKKU) in South Korea, led in part by Director Young Hee Lee, have created a high performance transistor using black phosphorus (BP) which has revealed some fascinating results.

Transistors are made up of materials with semiconducting properties, which come in two varieties: n-type (excess electrons) and p-type (excess holes). With the BP crystal, researchers have discovered that they can change its thickness and/or the contact metals and that will determine if it is high performance n-type, p-type, or ambipolar (function as both n- or p-type) material.

Atomic structure of black phosphorus monolayer

Sibplicon has to be extrinsically doped (inserting another element into its crystal structure) to make it n-type or p-type in order for it to work in a semiconductor chip.   The BP crystals can operate as both n-type and p-type or something in between, but don’t require extrinsic doping.  This means that instead of having to fabricate a silicon-arsenic crystal sandwiched between silicon-boron crystals, a transistor can have a single, lightweight, pure black phosphorus logic chip — no doping required.

Additionally, changing the metals used to connect the chip to the circuit has an influence on whether BP will be n- or p-type.  Instead of doping to make an n- and p-type material, both n- and p-type BP can be put all together on one chip just by changing its thickness and the contact metal used.

Source: http://www.ibs.re.kr/

Graphene Nanoribbons Boost Electronics

Graphene, an atom-thick material with extraordinary properties, is a promising candidate for the next generation of dramatically faster, more energy-efficient electronics. However, scientists have struggled to fabricate the material into ultra-narrow strips, called nanoribbons, that could enable the use of graphene in high-performance semiconductor electronics.

Now, University of Wisconsin-Madison engineers have discovered a way to grow graphene nanoribbons with desirable semiconducting properties directly on a conventional germanium semiconductor wafer. This advance could allow manufacturers to easily use graphene nanoribbons in hybrid integrated circuits, which promise to significantly boost the performance of next-generation electronic devices. The technology could also have specific uses in industrial and military applications, such as sensors that detect specific chemical and biological species and photonic devices that manipulate light.

In a paper published Aug. 10 in the journal Nature Communications, Michael Arnold, an associate professor of materials science and engineering at UW-Madison, Ph.D. student Robert Jacobberger, and their collaborators describe their new approach to producing graphene nanoribbons. Importantly, their technique can easily be scaled for mass production and is compatible with the prevailing infrastructure used in semiconductor processing.

graphene nanoribbonsProgressively zoomed-in images of graphene nanoribbons grown on germanium. The ribbons automatically align perpendicularly and naturally grow in what is known as the armchair edge configuration.

 

 

Graphene nanoribbons that can be grown directly on the surface of a semiconductor like germanium are more compatible with planar processing that’s used in the semiconductor industry, and so there would be less of a barrier to integrating these really excellent materials into electronics in the future,” Arnold says.

Source: http://news.wisc.edu/

Electric Cars: How To Improve Batteries

One big problem faced by electrodes in rechargeable batteries, as they go through repeated cycles of charging and discharging, is that they must expand and shrink during each cycle — sometimes doubling in volume, and then shrinking back. This can lead to repeated shedding and reformation of its “skin” layer that consumes lithium irreversibly, degrading the battery’s performance over time.

Image with 2014 Renault

Image with 2014 Renault

Now a team of researchers at MIT and Tsinghua University in China has found a novel way around that problem: creating an electrode made of nanoparticles with a solid shell, and a “yolk” inside that can change size again and again without affecting the shell. The innovation could drastically improve cycle life, the team says, and provide a dramatic boost in the battery’s capacity and power.

The new findings, which use aluminum as the key material for the lithium-ion battery’s negative electrode, or anode, are reported in the journal Nature Communications, in a paper by MIT professor Ju Li and six others. The use of nanoparticles with an aluminum yolk and a titanium dioxide shell has proven to be “the high-rate champion among high-capacity anodes,” the team reports.

Source: https://newsoffice.mit.edu/

Nanotechnology: The Brillant Future Of CubeSats

To understand why CubeSats could be the next big thing in the study of comets and asteroids, consider the story of Philae, the European Space Agency (ESA) probe that recently made history with the first-ever landing on the surface of a comet. The idea was to get close enough to the comet to analyze its composition in situ—what scientists call “ground truthing.” You can only learn so much about small bodies by studying them from Earth, so scientists built and launched the first spacecraft to sample a comet directly. Trouble is, Philae cost around $240 million, and we almost lost it. Harpoons designed to help the lander grab on to the comet in the low gravity failed to deploy. Another smidgeon of velocity in its bounce, and that $240 million would have been drifting uselessly in the comet’s wake. Philae was lucky; after another bounce it finally came to rest on the surface. But comet landings remain an inherently risky business. That’s where CubeSats—which can cost in the tens of thousands rather than the hundreds of millions of dollars—start to look appealing.
cubesats
Because CubeSat is low-cost, one can afford to tolerate more risks,” says USC’s Joseph Wang, who has been working on CubeSat engineering for the past several years. In theory, low cost means that scientists can afford to explore more small bodies, more often. The challenge is designing small, light instruments with enough capability to do serious science.

Source: http://www.airspacemag.com/

Fuel Cell Electrodes 7 Times More Efficient

A new fabrication technique that produces platinum hollow nanocages with ultra-thin walls could dramatically reduce the amount of the costly metal needed to provide catalytic activity in such applications as fuel cells. The technique uses a solution-based method for producing atomic-scale layers of platinum to create hollow, porous structures that can generate catalytic activity both inside and outside the nanocages. The layers are grown on palladium nanocrystal templates, and then the palladium is etched away to leave behind nanocages approximately 20 nanometers in diameter, with between three and six atom-thin layers of platinum. Use of these nanocage structures in fuel cell electrodes could increase the utilization efficiency of the platinum by a factor of as much as seven, potentially changing the economic viability of the fuel cells.
platinum-nanocages

A transmission electron microscope image shows a typical sample of platinum cubic nanocages

We can get the catalytic activity we need by using only a small fraction of the platinum that had been required before,” said Younan Xia, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. Xia also holds joint faculty appointments in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech. “We have made hollow nanocages of platinum with walls as thin as a few atomic layers because we don’t want to waste any material in the bulk that does not contribute to the catalytic activity.
The research – which also involved researchers at the University of Wisconsin-Madison, Oak Ridge National Laboratory, Arizona State University and Xiamen University in China – was reported in the July 24 issue of the journal Science.

Source: http://www.news.gatech.edu/

How To Make Solar Energy Conversion More Efficient

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense.  The solar cells – made often of silicon or cadmium telluride – rarely cost more than 20 percent of the total costSolar energy could be made cheaper if less land had to be purchased to accommodate solar panels, best achieved if each solar cell could be coaxed to generate more power.

A huge gain in this direction has now been made by a team of chemists at the University of California, Riverside (UCR) that has found an ingenious way to make solar energy conversion more efficientThe researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in “upconvertingphotons in the visible and near-infrared regions of the solar spectrum.

 

Solar-panels UCRChemists at the University of California, Riverside have found an ingenious way to make solar energy conversion more efficient

The infrared region of the solar spectrum passes right through the photovoltaic materials that make up today’s solar cells,” explained Christopher Bardeen, a professor of chemistry. The research was a collaborative effort between him and Ming Lee Tang, an assistant professor of chemistry. “This is energy lost, no matter how good your solar cell.  The hybrid material we have come up with first captures two infrared photons that would normally pass right through a solar cell without being converted to electricity, then adds their energies together to make one higher energy photon.  This upconverted photon is readily absorbed by photovoltaic cells, generating electricity from light that normally would be wasted.”

Source: http://ucrtoday.ucr.edu/

Ultrathin Electronics At Nano Scale

Semiconductors, metals and insulators must be integrated to make the transistors that are the electronic building blocks of your smartphone, computer and other microchip-enabled devices. Today’s transistors are miniscule—a mere 10 nanometers wide—and formed from three-dimensional (3D) crystals.

But a disruptive new technology looms that uses two-dimensional (2D) crystals, just 1 nanometer thick, to enable ultrathin electronics. Scientists worldwide are investigating 2D crystals made from common layered materials to constrain electron transport within just two dimensions. Researchers had previously found ways to lithographically pattern single layers of carbon atoms called graphene into ribbon-like “wires” complete with insulation provided by a similar layer of boron nitride. But until now they have lacked synthesis and processing methods to lithographically pattern junctions between two different semiconductors within a single nanometer-thick layer to form transistors, the building blocks of ultrathin electronic devices. Now for the first time, researchers at the Department of Energy’s Oak Ridge National Laboratory (ONRL) have combined a novel synthesis process with commercial electron-beam lithography techniques to produce arrays of semiconductor junctions in arbitrary patterns within a single, nanometer-thick semiconductor crystal.

scalable arrays of semiconductor junctions

We can literally make any kind of pattern that we want,” said Masoud Mahjouri-Samani, who co-led the study with David Geohegan. Geohegan, head of ORNL’s Nanomaterials Synthesis and Functional Assembly Group at the Center for Nanophase Materials Sciences, is the principal investigator of a Department of Energy basic science project focusing on the growth mechanisms and controlled synthesis of nanomaterials.
Millions of 2D building blocks with numerous patterns may be made concurrently, Mahjouri-Samani added. In the future, it might be possible to produce different patterns on the top and bottom of a sheet.

Source: http://www.ornl.gov/

Yarns that store and release electrical power

Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough power to transmit data. Now, researchers at MIT and in Canada have found a promising new approach to delivering the short but intense bursts of power needed by such small devices. The key is a new approach to making supercapacitors — devices that can store and release electrical power in such bursts, which are needed for brief transmissions of data from wearable devices such as heart-rate monitors, computers, or smartphones, the researchers say. They may also be useful for other applications where high power is needed in small volumes, such as autonomous microrobots.

The new approach uses yarns, made from nanowires of the element niobium, as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between). The concept is described in a paper in the journal ACS Applied Materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili, and three others at the University of British Columbia.

Nanotechnology researchers have been working to increase the performance of supercapacitors for the past decade. Among nanomaterials, carbon-based nanoparticles — such as carbon nanotubes and graphene — have shown promising results, but they suffer from relatively low electrical conductivity, Mirvakili says.

In this new work, he and his colleagues have shown that desirable characteristics for such devices, such as high power density, are not unique to carbon-based nanoparticles, and that niobium nanowire yarn is a promising an alternative.

MIT-Nanowires-1Yarn made of niobium nanowires, seen here in a scanning electron microscope image (background), can be used to make very efficient supercapacitors, MIT researchers have found. Adding a coating of a conductive polymer to the yarn (shown in pink, inset) further increases the capacitor’s charge capacity. Positive and negative ions in the material are depicted as blue and red spheres.

Imagine you’ve got some kind of wearable health-monitoring system,” Hunter says, “and it needs to broadcast data, for example using Wi-Fi, over a long distance.” At the moment, the coin-sized batteries used in many small electronic devices have very limited ability to deliver a lot of power at once, which is what such data transmissions need.

Long-distance Wi-Fi requires a fair amount of power,” says Hunter, the George N. Hatsopoulos Professor in Thermodynamics in MIT’s Department of Mechanical Engineering, “but it may not be needed for very long.” Small batteries are generally poorly suited for such power needs, he adds.

We know it’s a problem experienced by a number of companies in the health-monitoring or exercise-monitoring space. So an alternative is to go to a combination of a battery and a capacitor,” Hunter says: the battery for long-term, low-power functions, and the capacitor for short bursts of high power. Such a combination should be able to either increase the range of the device, or — perhaps more important in the marketplace — to significantly reduce size requirements.

Source: https://newsoffice.mit.edu/

Electric Planes Cross The Channel

Airbus Group  Friday completed its first-ever flight of an electric plane across the English Channel as the European plane maker seeks to spark interest in less polluting aircraft.

E fan

Airbus’s two-seat E-Fan demonstrator plane powered exclusively by lithium-batteries took 36 minutes to fly from Lydd in southern England to Calais, France, on the historic hop. It came soon after the single-seat Solar Impulse 2 flew from Japan to Hawaii in the longest-ever solar-powered flight as part of an around-the-world journey.

Just as cars are moving from burning fossil fuels to battery power, aircraft makers are exploring a similar shift to reduce carbon dioxide emissions. “It’s a big steppingstone,” said Jean Botti, chief technical officer at Airbus.

Private pilot Hugues Duval beat Airbus to the bragging rights of completing the first-ever Channel crossing in an electric plane when he traversed the body of water on Thursday in his single-seat Cri-Cri plane.

Airbus, better known for making airliners seating more than 100 passengers, plans to start delivering two-seat production versions of the E-Fan in 2017 through its VoltAir subsidiary.

A four-seat E-Fan 4.0 could follow 18 months later. It would introduce hybrid technology that could provide a springboard to building regional planes carrying 100 passengers, Mr. Botti said.

Source: http://www.airbusgroup.com/