#Researchers find nanowires have pronounced unusually'anelastic'properties Anelastic materials exhibit gradual full recovery of deformation once a load is removed, leading to efficient dissipation of internal mechanical energy.
and p-doped Si nanowires (NWS) can exhibit anelastic behaviour that is up to four orders of magnitude larger than the largest anelasticity observed in bulk materials, with a recovery time-scale in the order
Researchers from North carolina State university and Brown University have found that nanoscale wires (nanowires) made of common semiconductor materials have pronounced a anelasticity-meaning that the wires,
"Because nanowires are so small, the anelasticity is significant and easily observed --although it was a total surprise
when we first discovered the anelasticity in nanowires.""The anelasticity was discovered when Zhu and his students were studying the buckling behavior of nanowires."
"Anelasticity is a fundamental mechanical property of nanowires, and we need to understand these sort of mechanical behaviors
if we want to incorporate nanowires into electronics or other devices,"says Elizabeth Dickey, a professor of materials science and engineering at NC State and co-author of the paper.
Nanowires hold promise for use in a variety of applications, including flexible, stretchable and wearable electronic devices.
The researchers worked with both zinc oxide and silicon nanowires, and found that -when bent-the nanowires would return more than 80 percent of the way to their original shape instantaneously,
but return the rest of the way (up to 20 percent) slowly.""In nanowires that are approximately 50 nanometers in diameter,
it can take 20 or 30 minutes for them to recover that last 20 percent of their original shape,
"says Guangming Cheng, a Ph d. student in Zhu's lab and the first author for the paper.
The work was done using tools developed in Zhu's group that enabled the team to conduct experiments on nanowires
If you think of the bent nanowire as an arch, the atoms are moving from the inside of the arch to the outside.
"This phenomenon is pronounced in nanowires. For instance, zinc oxide nanowires exhibited anelastic behavior that is up to four orders of magnitude larger than the largest anelasticity observed in bulk materials,
with a recovery time-scale in the order of minutes,"says Huajian Gao, a professor at Brown University and co-corresponding author of the paper.
Detailed modeling by Gao's group indicates that the pronounced anelasticity in nanowires is because it is much easier for atoms to move through nanoscale materials than through bulk materials.
nanowires can be bent much further than thicker wires without becoming permanently deformed or breaking.""A reviewer commented that this is a new important page in the book on mechanics of nanostructures,
#Nanowires give'solar fuel cell'efficiency a tenfold boost: Eindhoven researchers make important step towards a solar cell that generates hydrogen A solar cell that produces fuel rather than electricity.
Processing the gallium phosphide in the form of very small nanowires is novel and helps to boost the yield by a factor of ten.
The researchers have overcome this problem by making a grid of very small Gap nanowires, measuring five hundred nanometers (a millionth of a millimeter) long and ninety nanometers thick.
"For the nanowires we needed ten thousand less precious Gap material than in cells with a flat surface.
Each consisted of a plasmonic gold nanowire atop a semiconducting layer of titanium dioxide. In the first setup, the gold sat directly on the semiconductor,
nanostructures (such as nanowires) must be paced into dense"nanostructure forests, "producing 3-D nanogeometries in which ions and electrons must rapidly move.
researchers lay out a mesh of nanowires sandwiched in layers of organic polymer. The first layer is dissolved then, leaving the flexible mesh,
"Laser-assembled nanowires For the first step in grid construction, the team took advantage of their recent invention of laser zone annealing (LZA) to produce the extremely localized thermal spikes needed to drive ultra-fast self-assembly.
and transforms them into functional nanowires. Layer-by-layer lattice The first completed nanowire array acts as the foundation of the full lattice.
Additional layers each one following variations on that same process, are stacked then to produce customized, crisscrossing configurationsike chain-link fences 10,000 times thinner than a human hair."
"The direction of the laser sweeping across each unassembled layer determines the orientation of the nanowire rows,
"For example, a single layer of platinum nanowires conducts electricity in only one direction, but a two-layer mesh conducts uniformly in all directions."
and selectively filled via epitaxy to create arbitrary shaped III-V semiconductors such as nanowires, cross junctions, nanostructures containing constrictions and 3d stacked nanowires.
Using this small seed area epitaxy, today at the VLSI Symposium in Kyoto, IBM scientist Lukas Czornomaz is presenting a solution for large scale and controlled integration of high quality Ingaas on bulk Silcon (Si)
#Novel method creates nanowires with new useful properties (Nanowerk News) Harvard scientists have developed a first-of-its-kind method of creating a class of nanowires that one day could have applications in areas ranging from consumer electronics to solar panels.
but researchers for years have recognized a similar phenomenon in nanowires. When heated to extreme temperatures
Day and Mankin heated traditionally grown nanowires to just below that transformation point in a vacuum chamber,
when nanowires break down at high temperatures. Unlike with the droplets, though, the process can be controlled tightly.
Along with duplicating the process in nanowires between 20 and 100 nanometers in diameter, researchers demonstrated the process using several combinations of materials,
In addition to being able to tune the distance between the lobes on nanowires, Mankin said tests showed they were also able to tune the cross-section of the wires.
What that means is that you could absorb the same amount of infrared light with these nanowires as you could with traditional silicon materials that are 100 times thicker.
if you wanted to use nanowires for photo-detection of green and blue light, youd need two wires,
researchers lay out a mesh of nanowires sandwiched in layers of organic polymer. The first layer is dissolved then, leaving the flexible mesh,
the secret to these new prototype solar cells are gallium phosphide nanowires, which can split water into its hydrogen
So the researchers tried producing a grid of tiny gallium phosphide nanowires measuring 90 nanometres thick and 500 nanometers long,
"For the nanowires we needed 10,000 less precious Gap material than in cells with a flat surface.
#New superconducting hybrid crystals A new type of'nanowire'crystals that fuses semiconducting and metallic materials on the atomic scale could lay the foundation for future semiconducting electronics.
"Our new material was born as a hybrid between a semiconducting nanowire and its electronic contact.
Thus we have invented a way to make a perfect transition between the nanowire and a superconductor.
ever since research into nanowire crystals has existed at the Nanoscience Center at the Niels Bohr Institute.
Nanowire and contact formed at the same time Nanowires are extremely thin nanocrystal threads used in the development of new electronic components
Part of the challenge of working with nanowires is creating a good transition between these nanowires and an electrical contact to the outside world.
but from all over the world, have cultured nanowires and the contact separately. However, with the new approach, both the quality and the reproducibility of the contact have improved considerably."
"The atoms sit in a perfectly ordered lattice in the nanowire crystal, not only in the semiconductor and the metal,
You could say that it is the ultimate limit to how perfect a transition one could imagine between a nanowire crystal and a contact.
Chips with billions of nanowire hybrids In their publication in Nature Materials, the research group has demonstrated this perfect contact
and its properties and has shown also that they can make a chip with billions of identical semiconductor-metal nanowire hybrids."
and that is why the research into nanowires is interesting for the largest electronics companies, "says Thomas Sand Jespersen.
#Nanowire clothing could keep people warm without heating everything else To stay warm when temperatures drop outside,
But scientists have developed now a novel nanowire coating for clothes that can both generate heat
the special nanowire cloth trapped body heat far more effectively. Because the coatings are made out of conductive materials,
and transforms them into functional nanowires. Arraythe first completed nanowire array acts as the foundation of the full lattice.
Additional layers each one following variations on that same process, are stacked then to produce customized, crisscrossing configurations--like chain-link fences 10,000 times thinner than a human hair."
"The direction of the laser sweeping across each unassembled layer determines the orientation of the nanowire rows,
"For example, a single layer of platinum nanowires conducts electricity in only one direction, but a two-layer mesh conducts uniformly in all directions."
thin slivers of silver nanowires. The silver nanowires are tiny, averaging#150 nm in diameter and#30 m in length (a human hair ranges from 17 to 181 m). The nanowires were mixed into a liquid elastic material
which is both soft and stretchy when dry. To ensure that the material remains tight on the target area while heating,
the team devised a 2-D interlocking coil pattern for the mesh structure. To make the mesh,
to promote the growth of silicon nanowires and to induce gold-based patterns in the silicon.
#Transparent, electrically conductive network of encapsulated silver nanowires The electrodes for connections on the"sunny side"of a solar cell need to be not just electrically conductive,
Mesh of silver nanowires Manuela Göbelt on the team of Prof. Silke Christiansen has developed now an elegant new solution using only a fraction of the silver
The doctoral student initially made a suspension of silver nanowires in ethanol using wet-chemistry techniques. She then transferred this suspension with a pipette onto a substrate, in this case a silicon solar cell.
the silver nanowires organise themselves into a loose mesh that remains transparent, yet dense enough to form uninterrupted current paths.
This process caused tiny AZO crystals to form on the silver nanowires, enveloped them completely, and finally filled in the interstices.
The silver nanowires measuring about 120 nanometres in diameter, were covered with a layer of about 100 nanometres of AZO
However, its performance depends on how well the nanowires are interconnected, which is a function of the wire lengths and the concentration of silver nanowires in the suspension.
The scientists were able to specify the degree of networking in advance with computers. Using specially developed image analysis algorithms,
"We are investigating where a given continuous conductive path of nanowires is interrupted to see where the network is not yet optimum,
"The network of silver nanowires is so fine that almost no light for solar energy conversion is lost in the cell due to the shadow,
On the contrary, she hopes"it might even be possible for the silver nanowires to scatter light into the solar cell absorbers in a controlled fashion through
Nanowires that poke out can be connected to a computer to take recordings and stimulate cells. So far, the researchers have implanted meshes consisting of 16 electrical elements into two brain regions of anaesthetized mice
and to add hairpin-shaped nanowire probes to the mesh to record electrical activity inside and outside cells.
a team of Harvard researchers describe the creation of a flexible nanowire mesh with nanoscale electrodes
Nanowires connecting the mesh with computers in the outside world can either record brain activity or stimulate nearby neurons.
so Bailie did it manually. e used a sheet of plastic with silver nanowires on it, he said. hen we built a tool that uses pressure to transfer the nanowires onto the perovskite cell, kind of like a temporary tattoo.
You just need to rub it to transfer the film. Remarkable efficiency For the experiment, the Stanford team stacked a perovskite solar cell with an efficiency of a 12.7 percent on top of a low-quality silicon cell with an efficiency of just 11.4 percent. y combining two cells
researchers lay out a mesh of nanowires sandwiched in layers of organic polymer. The first layer is dissolved then, leaving the flexible mesh,
#Nanowire implants offer remote-controlled drug delivery A team of Purdue University researchers developed a new implantable drug-delivery system using the nanowires,
A team of researchers has created a new implantable drug-delivery system using nanowires that can be controlled wirelessly.
The nanowires respond to an electromagnetic field generated by a separate device, which can be used to control the release of a preloaded drug.
The nanowires are made of polypyrrole, a conductive polymer material that responds to electromagnetic fields. Wen Gao, a postdoctoral researcher in the Center for Paralysis Research who worked on the project with Borgens,
grew the nanowires vertically over a thin gold base, like tiny fibers making up a piece of shag carpet hundreds of times smaller than a human cell.
The nanowires can be loaded with a drug and when the correct electromagnetic field is applied, the nanowires release small amounts of the payload.
This process can be started and stopped at will, like flipping a switch, by using the corresponding electromagnetic field stimulating device,
and transported a patch of the nanowire carpet on water droplets that were used used to deliver it to the site of injury.
The nanowire patches adhere to the site of injury through surface tension, Gao said. The magnitude and wave form of the electromagnetic field must be tuned to obtain the optimum release of the drug
Functional Drug Delivery Using Electromagnetic field-Responsive Polypyrrole Nanowires, was published in the journal Langmuir. Other team members involved in the research include John Cirillo,
A 1-2 millimeter patch of the nanowires doped with dexamethasone was placed onto spinal cord lesions that had been exposed surgically,
and those that received a nanowire patch but were exposed not to the electromagnetic field. In some cases, treated mice had no detectable GFAP signal.
#NRL Researchers First to Detect Spin Precession in Silicon nanowires Scientists at the U s. Naval Research Laboratory (NRL) have reported the first observation of spin precession of spin currents flowing in a silicon nanowire
and the green line is the silicon nanowire transport channel. The bright dot on the end of the nanowire is used the gold nanoparticle to seed the nanowire growth.
The NRL research team observed spin precession (the Hanle effect) for both the spin-polarized charge near the contact interface and for pure spin currents flowing in the NW channel.
Semiconductor nanowires provide an avenue to further reduce the ever-shrinking dimensions of transistors. Including electron spin as an additional state variable offers new prospects for information processing,
or hexagonal boron nitride as tunnel contacts on nanowires offers many advantages over conventional materials deposited by vapor deposition (such as Al2o3
This increase would further improve the performance of nanowire spintronic devices by providing higher signal to noise ratios
and corresponding operating speeds, advancing the techological applications of nanowire devices. The NRL research team includes Dr. Olaf van Erve, Dr. Adam Friedman, Dr. Connie Li,
to promote the growth of silicon nanowires and to induce gold-based patterns in the silicon.
#New Technique to Synthesize Nanostructured Nanowires IBM scientist Frances Ross (left) with Brookhaven Lab scientists Dong Su (center) and Eric Stach in the Center for Functional Nanomaterials.
The researchers have developed a method for growing combinations of different materials in a needle-shaped crystal called a nanowire.
Nanowires are small structures, only a few billionths of a metre in diameter. Semiconductors can be grown into nanowires
and the result is a useful building block for electrical, optical, and energy harvesting devices. The researchers have found out how to grow smaller crystals within the nanowire,
forming a structure like a crystal rod with an embedded array of gems. Details of the new method are published in the journal Nature Materials.
Electron microscope images showing the formation of a nickel silicide nanoparticle (colored yellow) in a silicon nanowire.
and feed the nanowire, so that it self-assembles one atomic layer at a time. VLS allows a high degree of control over the resulting nanowire:
composition, diameter, growth direction, branching, kinking and crystal structure can be controlled by tuning the self-assembly conditions.
As nanowires become better controlled, new applications become possible. The technique that Hofmann and his colleagues from Cambridge and IBM developed can be thought of as an expansion of the concept that underlies conventional VLS growth.
not only to grow the nanowire, but also to form new materials within it. These tiny crystals form in the liquid,
but later attach to the nanowire and then become embedded as the nanowire is grown further. This catalyst mediated docking process can elf-optimiseto create highly perfect interfaces for the embedded crystals.
To unravel the complexities of this process the research team used two customised electron microscopes, one at IBM TJ Watson Research center and a second at Brookhaven National Laboratory.
This allowed them to record high-speed movies of the nanowire growth as it happens atom-by-atom.
resulted in complex structures consisting of nanowires with embedded nanoscale crystals, or quantum dots, of controlled size and position. he technique allows two different materials to be incorporated into the same nanowire,
even if the lattice structures of the two crystals don perfectly match, said Hofmann. t a flexible platform that can be used for different technologies. ossible applications for this technique range from atomically perfect buried interconnects to single-electron transistors, high-density memories, light emission, semiconductor lasers,
Ning group started pursuing the distinctive properties of nanomaterials, such as nanowires or nanosheets, more than 10 years ago.
Six years ago, under U s army Research Office funding, they demonstrated that one could indeed grow nanowire materials in a wide range of energy bandgaps
Later on they realized simultaneous laser operation in green and red from a single semiconductor nanosheet or nanowires.
and to lithographically define oxide templates and fill them via epitaxy, making nanowires, cross junctions,
nanostructures containing constrictions and 3d stacked nanowires. According to Schmid, more work is required before the same level of control can be exerted over III-V materials as currently exists for silicon,
They used extremely thin nanowires that were made of indium arsenide to fabricate the quantum dots. The placed the qubits 6 mm apart in a cavity that was made from niobium at a temperature near absolute zero(-459 degrees Fahrenheit.
< Back - Next >
Overtext Web Module V3.0 Alpha
Copyright Semantic-Knowledge, 1994-2011