Posts belonging to Category NEMS



Semiconductors As Thin As An Atom

A two-dimensional material developed by physicist Prof. Dr. Axel Enders (Bayreuth University  in Germany) together with international partners could revolutionize electronicsSemiconductors that are as thin as an atom are no longer the stuff of .  Thanks to its semiconductor properties, this material could be much better suited for high tech applications than graphene, the discovery of which in 2004 was celebrated worldwide as a . This new material contains carbon, boron, and nitrogen, and its chemical name is “Hexagonal Boron-Carbon-Nitrogen (h-BCN)”. The new development was published in the journal ACS Nano.

2D material Bayreuth University

Our findings could be the starting point for a new generation of electronic transistors, circuits, and sensors that are much smaller and more bendable than the electronic elements used to date. They are likely to enable a considerable decrease in power consumption,” Prof. Enders predicts, citing the CMOS technology that currently dominates the electronics industry. This technology has clear limits with regard to further miniaturization. “h-BCN is much better suited than graphene when it comes to pushing these limits,” according to Enders.

Graphene is a two-dimensional lattice made up entirely of carbon atoms. It is thus just as thin as a single atom. Once scientists began investigating these structures more closely, their remarkable properties were greeted with enthusiasm across the world. Graphene is 100 to 300 times stronger than steel and is, at the same time, an excellent conductor of heat and electricity.

Source: https://www.uni-bayreuth.de/

Nanocomputer: Carbon Nanotube Transistors Outperform Silicon

For decades, scientists have tried to harness the unique properties of carbon nanotubes to create high-performance electronics that are faster or consume less power — resulting in longer battery life, faster wireless communication and faster processing speeds for devices like smartphones and laptops. But a number of challenges have impeded the development of high-performance transistors made of carbon nanotubes, tiny cylinders made of carbon just one atom thick. Consequently, their performance has lagged far behind semiconductors such as silicon and gallium arsenide used in computer chips and personal electronics.

Now, for the first time, University of Wisconsin–Madison materials engineers have created carbon nanotube transistors that outperform state-of-the-art silicon transistors. Led by Michael Arnold and Padma Gopalan, UW–Madison professors of materials science and engineering, the team’s carbon nanotube transistors achieved current that’s 1.9 times higher than silicon transistors. The researchers reported their advance in a paper published in the journal Science Advances.

carbon nanotube integrated circuits

This achievement has been a dream of nanotechnology for the last 20 years,” says Arnold. “Making carbon nanotube transistors that are better than silicon transistors is a big milestone. This breakthrough in carbon nanotube transistor performance is a critical advance toward exploiting carbon nanotubes in logic, high-speed communications, and other semiconductor electronics technologies.”

This advance could pave the way for carbon nanotube transistors to replace silicon transistors and continue delivering the performance gains the computer industry relies on and that consumers demand. The new transistors are particularly promising for wireless communications technologies that require a lot of current flowing across a relatively small area.

Source: http://news.wisc.edu/

Smart Windows Control Light and Heat, Save Energy

View, previously Soladigm, is a Californian company working on the development of energy-saving smart windows based on electrochromism that can control light and heat while maintaining view and reducing glareView smart nanotechnology glass is now installed  in 250 commercial buildings.

VIEW smart glassCLICK ON THE IMAGE TO ENJOY THE VIDEO

Solar radiation and glare are reduced when the View glass is tinted, creating a comfortable indoor climate for occupants. By admitting natural daylight and rejecting unwanted solar glare, View Dynamic Glass significantly reduces annual energy costs. Control View Dynamic Glass from anywhere, create schedules, track energy efficiency and manage entire buildings with our mobile app.
View Dynamic Glass uses a proprietary electrochromic process to create smart glass in a world-class manufacturing facility. The best talent, equipment, and processes from the semiconductor, flat panel and solar industries produce dynamic glass in sizes up to 6 feet by 10 feet in many custom configurations. The factory combines leading-edge glass manufacturing with high technology processes and controls to deliver products that save energy, minimize heat and glare and allow occupants to enjoy the view to the outdoors. View Dynamic Glass is specified by architects for product performance, durability and energy savings.

Source: http://www.nextbigfuture.com/

How To Increase By Six Times The Capacity Of Lithium-Ion Batteries

The capacity of lithium-ion batteries might be increased by six times by using anodes made of silicon instead of graphite. A team from the Helmholtz-Zentrum Berlin (HZB) Institute of Soft Matter and Functional Materials has observed for the first time in detail how lithium ions migrate into thin films of silicon. It was shown that extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.

The team was able to show through neutron measurements made at the Institut Laue-Langevin in Grenoble, France, that lithium ions do not penetrate deeply into the silicon. During the charge cycle, a 20-nm anode layer develops containing an extremely high proportion of lithium. This means extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.
lithium-ion battery

Lithium-ion batteries provide laptops, smart phones, and tablet computers with reliable energy. However, electric vehicles have not gotten as far along with conventional lithium-ion batteries. This is due to currently utilised electrode materials such as graphite only being able to stably adsorb a limited number of lithium ions, restricting the capacity of these batteries. Semiconductor materials like silicon are therefore receiving attention as alternative electrodes for lithium batteries. Bulk silicon is able to absorb enormous quantities of lithium. However, the migration of the lithium ions destroys the crystal structure of silicon. This can swell the volume by a factor of three, which leads to major mechanical stresses. Now a team from the HZB Institute for Soft Matter and Functional Materials headed by Prof. Matthias Ballauff has directly observed for the first time a lithium-silicon half-cell during its charging and discharge cycles. “We were able to precisely track where the lithium ions adsorb in the silicon electrode using neutron reflectometry methods, and also how fast they were moving”, comments Dr. Beatrix-Kamelia Seidlhofer, who carried out the experiments using the neutron source located at the Institute Laue-Langevin.

She discovered two different zones during her investigations. Near the boundary to the electrolytes, a roughly 20-nm layer formed having extremely high lithium content: 25 lithium atoms were lodged among 10 silicon atoms. A second adjacent layer contained only one lithium atom for ten silicon atoms. Both layers together are less than 100 nm thick after the second charging cycle.

After discharge, about one lithium ion per silicon node in the electrode remained in the silicon boundary layer exposed to the electrolytes. Seidlhofer calculates from this that the theoretical maximum capacity of these types of silicon-lithium batteries lies at about 2300 mAh/g. This is more than six times the theoretical maximum attainable capacity for a lithium-ion battery constructed with graphite (372 mAh/g).

The results ar published in the journal ACSnano (DOI: 10.1021/acsnano.6b02032).

Source: https://www.helmholtz-berlin.de/

Stamp Hard Disk For NanoComputer Contains All Books Ever Written

Every day, modern society creates more than a billion gigabytes of new data. To store all this data, it is increasingly important that each single bit occupies as little space as possible. A team of scientists at the Kavli Institute of Nanoscience at Delft University (Netherlands) managed to bring this reduction to the ultimate limit: they built a memory of 1 kilobyte (8,000 bits), where each bit is represented by the position of one single chlorine atom.
In 1959, physicist Richard Feynman challenged his colleagues to engineer the world at the smallest possible scale. In his famous lecture There’s Plenty of Room at the Bottom, he speculated that if we had a platform allowing us to arrange individual atoms in an exact orderly pattern, it would be possible to store one piece of information per atom. To honor the visionary Feynman, Otte and his team now coded a section of Feynman’s lecture on an area 100 nanometers wide
Hard disk for nanocomputer

In theory, this storage density would allow all books ever created by humans to be written on a single post stamp”, says lead-scientist Sander Otte. They reached a storage density of 500 Terabits per square inch (Tbpsi), 500 times better than the best commercial hard disk currently available. His team reports on this memory in Nature Nanotechnology on Monday July 18.

Source: http://www.tudelft.nl/

6.3 nanometre lens to revolutionise cameras

Scientists have created the world’s thinnest lens, one two-thousandth the thickness of a human hair, opening the door to flexible computer displays and a revolution in miniature cameras. Lead researcher Dr Yuerui (Larry) Lu from ANU Research School of Engineering  (Australia) said the discovery hinged on the remarkable potential of the molybdenum disulphide crystal.

nanometre lens

This type of material is the perfect candidate for future flexible displays,” said Dr Lu, leader of Nano-Electro-Mechanical System (NEMS) Laboratory in the ANU Research School of Engineering. “We will also be able to use arrays of micro lenses to mimic the compound eyes of insects.”

The 6.3-nanometre lens outshines previous ultra-thin flat lenses, made from 50-nanometre thick gold nano-bar arrays, known as a metamaterial. “Molybdenum disulphide is an amazing crystal,” said Dr Lu. “It survives at high temperatures, is a lubricant, a good semiconductor and can emit photons too. “The capability of manipulating the flow of light in atomic scale opens an exciting avenue towards unprecedented miniaturisation of optical components and the integration of advanced optical functionalities.”

Molybdenum disulphide is in a class of materials known as chalcogenide glasses that have flexible electronic characteristics that have made them popular for high-technology components.

Source: https://cecs.anu.edu.au/

Infrared Vision Using Graphene Makes Man Superior To Predator

Movies such as 1987’s “Predator,” in which an alien who sees in the infrared hunts down Arnold Schwarzenegger and his team, introduced a generation of sci-fi fans to thermal imaging. Since then, heat-sensing devices have found many real-word applications but have remained relatively expensive and rigid. But a new development featuring graphene, reported in ACS’ journal Nano Letters, could lead to a flexible, transparent and low-cost infrared vision system.

predator

The concept of humans — or aliens — having the power to see in the infrared to help fight enemies in the dark has been around for decades. Technology has allowed real-life military, police, firefighters and others to do their jobs successfully at night and in smoky conditions. It also helps manufacturers and building inspectors identify overheating equipment or circuits. But currently, many of these systems require cryogenic cooling to filter out background radiation, or “noise,” and create a reliable image. This approach, however, complicates the design of these imaging devices, and adds to the cost and the unit’s bulkiness. Tomás Palacios, Pablo Jarillo-Herrero and colleagues wanted to find a more practical solution.

The researchers integrated graphene with silicon microelectromechanical systems (known as MEMS) to make their device. Testing showed it could be used to detect a person’s heat signature at room temperature without cryogenic cooling. In the future, advances could make the device even more versatile. The researchers say that a thermal sensor could be based on a single layer of graphene, which would make it transparent and flexible. Also, manufacturing could be simplified, which would bring costs down.

Source: http://www.acs.org/

Nanotube-based Transistor For Nanocomputers

Individual transistors made from carbon nanotubes are faster and more energy efficient than those made from other materials. Going from a single transistor to an integrated circuit full of transistors, however, is a giant leap.

carbon nanotube integrated circuits

A single microprocessor has a billion transistors in it,” said Northwestern Engineering’s Mark Hersam. “All billion of them work. And not only do they work, but they work reliably for years or even decades.

When trying to make the leap from an individual, nanotube-based transistor to wafer-scale integrated circuits, many research teams, including Hersam’s, have met challenges. For one, the process is incredibly expensive, often requiring billion-dollar cleanrooms to keep the delicate nano-sized components safe from the potentially damaging effects of air, water, and dust. Researchers have also struggled to create a carbon nanotube-based integrated circuit in which the transistors are spatially uniform across the material, which is needed for the overall system to work.

Now Hersam and his team have found a key to solving all these issues. The secret lies in newly developed encapsulation layers that protect carbon nanotubes from environmental degradation.

Supported by the Office of Naval Research and the National Science Foundation, the research appears online in Nature Nanotechology on September 7. Tobin J. Marks,  professor of materials science and engineering in the McCormick School of Engineering, coauthored the paper. Michael Geier, a graduate student in Hersam’s lab, was first author. “One of the realities of a nanomaterial, such as a carbon nanotube, is that essentially all of its atoms are on the surface,” said Hersam, the Walter P. Murphy Professor of Materials Science and Engineering. “So anything that touches the surface of these materials can influence their properties. If we made a series of transistors and left them out in the air, water and oxygen would stick to the surface of the nanotubes, degrading them over time. We thought that adding a protective encapsulation layer could arrest this degradation process to achieve substantially longer lifetimes.

Hersam compares his solution to one currently used for organic light-emitting diodes (LEDs), which experienced similar problems after they were first realized. Many people assumed that organic LEDs would have no future because they degraded in air. After researchers developed an encapsulation layer for the material, organic LEDs are now used in many commercial applications, including displays for smartphones, car radios, televisions, and digital cameras. Made from polymers and inorganic oxides, Hersam’s encapsulation layer is based on the same idea but tailored for carbon nanotubes.

To demonstrate proof of concept, Hersam developed nanotube-based static random-access memory (SRAM) circuits. SRAM is a key component of all microprocessors, often making up as much as 85 percent of the transistors in the central-processing unit in a common computer. To create the encapsulated carbon nanotubes, the team first deposited the carbon nanotubes from a solution previously developed in Hersam’s lab. Then they coated the tubes with their encapsulation layers.

Using the encapsulated carbon nanotubes, Hersam’s team successfully designed and fabricated arrays of working SRAM circuits. Not only did the encapsulation layers protect the sensitive device from the environment, but they improved spatial uniformity among individual transistors across the wafer. While Hersam’s integrated circuits demonstrated a long lifetime, transistors that were deposited from the same solution but not coated degraded within hours.

After we’ve made the devices, we can leave them out in air with no further precautions,” Hersam said. “We don’t need to put them in a vacuum chamber or controlled environment. Other researchers have made similar devices but immediately had to put them in a vacuum chamber or inert environment to keep them stable. That’s obviously not going to work in a real-world situation.”

Source: http://www.mccormick.northwestern.edu/

Graphene Boosts By 30 Percent Chips Speeds

A typical computer chip includes millions of transistors connected with an extensive network of copper wires. Although chip wires are unimaginably short and thin compared with household wires, both have one thing in common: in each case the copper is wrapped within a protective sheath. For years a material called tantalum nitride has formed a protective layer around chip wires.

Now Stanford-led experiments demonstrate that a different sheathing material, graphene, can help electrons scoot through tiny copper wires in chips more quickly.

Graphene is a single layer of carbon atoms arranged in a strong yet thin lattice. Stanford electrical engineer H.-S. Philip Wong says this modest fix, using graphene to wrap wires, could allow transistors to exchange data faster than is currently possible.  And the advantages of using graphene could become greater in the future as transistors continue to shrink.

graphene Stanford

“Researchers have made tremendous advances on all of the other components in chips, but recently there hasn’t been much progress on improving the performance of the wires,” he said.

Wong, the Willard R. and Inez Kerr Bell Professor in the School of Engineering, led a team of six researchers, including two from the University of Wisconsin-Madison, who will present their findings at the Symposia of VLSI Technology and Circuits in Kyoto, Japan, a leading venue for the electronics industry. Ling Li, a graduate student in electrical engineering at Stanford and first author of the research paper, will explain why changing the exterior wrapper on connecting wires can have such a big impact on chip performance.

Source: http://engineering.stanford.edu/

How To Double The Energy Capacity Of Li-Ion Batteries

Researchers from Singapore’s Institute of Bioengineering and Nanotechnology (IBN) of A*STAR and Quebec’s IREQ (Hydro-Québec’s research institute) have synthesized silicate-based nanoboxes that could more than double the energy capacity of lithium-ion batteries as compared to conventional phosphate-based cathodes. This breakthrough could hold the key to longer-lasting rechargeable batteries for electric vehicles and mobile devices.

electric car
Lithium-ion batteries are widely used to power many electronic devices, including smart phones, medical devices and electric vehicles. Their high energy density, excellent durability and lightness make them a popular choice for energy storage
IBN researchers have successfully achieved simultaneous control of the phase purity and nanostructure of Li2MnSiO4 for the first time,” said Professor Jackie Y. Ying, IBN Executive Director. “This novel synthetic approach would allow us to move closer to attaining the ultrahigh theoretical capacity of silicate-based cathodes for battery applications.”

Source: http://news.hydroquebec.com/

Laboratories-On-a-Chip

Newly developed tiny antennas, likened to spotlights on the nanoscale, offer the potential to measure food safety, identify pollutants in the air and even quickly diagnose and treat cancer, according to the Australian scientists who created them. The new antennas are cubic in shape. They do a better job than previous spherical ones at directing an ultra-narrow beam of light where it is needed, with little or no loss due to heating and scattering, they say.

In a paper published in the Journal of Applied Physics, from AIP Publishing, Debabrata Sikdar of Monash University in Victoria, Australia, and colleagues describe these and other envisioned applications for their nanocubes in “laboratories-on-a-chip.” The cubes, composed of insulating, rather than conducting or semiconducting materials as were the spherical versions, are easier to fabricate as well as more effective, he says.

Sikdar’s paper presents analysis and simulation of 200-nanometer dielectric (nonconductive) nanoncubes placed in the path of visible and near-infrared light sources. The nanocubes are arranged in a chain, and the space between them can be adjusted to fine-tune the light beam as needed for various applications. As the separation between cubes increases, the angular width of the beam narrows and directionality improves, the researchers say.

nanoantennas
Unidirectional nanoantennas induce directionality to any omnidirectional light emitters like microlasers, nanolasers or spasers, and even quantum dots,” Sikdar said in an interview. Spasers are similar to lasers, but employ minute oscillations of electrons rather than light. Quantum dots are tiny crystals that produce specific colors, based on their size, and are widely used in color televisions. “Analogous to nanoscale spotlights, the cubic antennas focus light with precise control over direction and beam width,” he said.
Source: http://www.aip.org/

Ultra Bendable Electronics

Electronic devices have shrunk rapidly in the past decades, but most remain as stiff as the same sort of devices were in the 1950s — a drawback if you want to wrap your phone around your wrist when you go for a jog or fold your computer to fit in a pocket. Researchers from South Korea have taken a new step toward more bendable devices by manufacturing a thin film that keeps its useful electric and magnetic properties even when highly curved.

nanoparticles od bismuth
This electron microscope image shows tiny nanoparticles of bismuth ferrite embedded in a polymer film. The film enhances the unique electric and magnetic properties of bismuth ferrite and preserves these properties even when bent
Bulk bismuth ferrite has crucial problems for some applications, such as a high leakage current which hinders the strong electric properties,” said YoungPak Lee, a professor at Hanyang University in Seoul, South Korea. Mixing nanoparticles of bismuth ferrite into a polymer improved the current-leakage problem, he said, and also gave the film flexible, stretchable properties.

Flexible multiferrorics could enable new wearable devices such as health monitoring equipment or virtual reality attire, Lee said. The multiferroric materials could be used in high-density, energy efficient memory and switches in such devices, he said.
The researchers describe the film in a paper published in the journal Applied Physics Letters, from AIP Publishing.

Source: http://www.aip.org/