#A crystal wedding in the nanocosmos Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Vienna University of Technology and the Maria Curie-Sklodowska University Lublin have succeeded in embedding nearly perfect semiconductor crystals
into a silicon nanowire. With this new method of producing hybrid nanowires, very fast and multifunctional processing units can be accommodated on a single chip in the future.
The research results will be published in the journal Nano Research. Nano-optoelectronics are considered the cornerstone of future chip technology,
but the research faces major challenges: on the one hand, electronic components must be accommodated into smaller and smaller spaces.
On the other hand, what are known as compound semiconductors are to be embedded into conventional materials. In contrast to silicon, many of such semiconductors with extremely high electron mobility could improve performance of the most modern silicon-based CMOS technology.
Scientists from the HZDR, Vienna University of Technology and Maria Curie-Sklodowska University Lublin have now come a step closer to both these targets:
they integrated compound semiconductor crystals made of indium arsenide (Inas) into silicon nanowires, which are suited ideally for constructing increasingly compact chips.
This integration of crystals was the greatest obstacle for such"hetero-nanowires"until now: beyond the nanometer range, crystal lattice mismatch always led to numerous defects.
The researchers have managed now a near-perfect production and embedding of the Inas crystals into the nanowires for the first time.
Implanted atoms form crystals in the liquid-Phase in order to carry out this process, ion beam synthesis and heat treatment with xenon flash-lamps were used, two technologies in
which the Ion beam Center of the HZDR has held experience for many years. The scientists initially needed to introduce a determined number of atoms precisely into the wires using ion implantation.
They then carried out the flash-lamp annealing of the silicon wires in their liquid-phase within a matter of only twenty milliseconds."
"A silicon oxide shell, measuring merely fifteen-nanometers-thick, maintains the form of the liquid nanowire,
"explains HZDR scientist Dr. Slawomir Prucnal, "while the implanted atoms form the indium arsenide crystals.""Dr. Wolfgang Skorupa, the head of the research group adds:"
"The atoms diffuse in the liquid-silicon-phase so rapidly that within milliseconds they form flawless mono-crystals delineated from their surroundings with nearly perfect interfaces."
"In the next step, the scientists want to implement different compound semiconductors into Silicon nanowires and also optimize the size and distribution of the crystals a
#Tiny laser sensor heightens bomb detection sensitivity New technology under development at the University of California,
Berkeley, could soon give bomb-sniffing dogs some serious competition. A team of researchers led by Xiang Zhang,
UC Berkeley professor of mechanical engineering, has found a way to dramatically increase the sensitivity of a light-based plasmon sensor to detect incredibly minute concentrations of explosives.
They noted that it could potentially be used to sniff out a hard-to-detect explosive popular among terrorists.
Their findings are to be published Sunday, July 20, in the advanced online publication of the journal Nature Nanotechnology.
They put the sensor to the test with various explosives 2 4-dinitrotoluene (DNT), ammonium nitrate and nitrobenzene and found that the device successfully detected the airborne chemicals at concentrations of 0. 67 parts per billion, 0. 4 parts per billion and 7. 2 parts
per million, respectively. One part per billion would be akin to a blade of grass on a football field.
The researchers noted that this is much more sensitive than the published results to date for other optical sensors."
"Optical explosive sensors are very sensitive and compact, "said Zhang, who is also director of the Materials science Division at the Lawrence Berkeley National Laboratory and director of the National Science Foundation Nanoscale Science and Engineering Center at UC Berkeley."
"The ability to magnify such a small trace of an explosive to create a detectable signal is a major development in plasmon sensor technology,
which is one of the most powerful tools we have today.""The new sensor could have many advantages over current bomb-screening methods."
"Bomb-sniffing dogs are expensive to train and they can become tired, "said study co-lead author Ren-Min Ma,
an assistant professor of physics at Peking University who did this work when he was a postdoctoral researcher in Zhang's lab."The other thing we see at airports is the use of swabs to check for explosive residue,
but those have relatively low-sensitivity and require physical contact. Our technology could lead to a bomb-detecting chip for a handheld device that can detect the tiny-trace vapor in the air of the explosive's small molecules."
"The sensor could also be developed into an alarm for unexploded land mines that are otherwise difficult to detect,
the researchers said. According to the United nations, landmines kill 15,000 to 20,000 people every year. Most of the victims are children, women and the elderly.
Unstable and hungry for electrons The nanoscale plasmon sensor used in the lab experiments is much smaller than other explosive detectors on the market.
It consists of a layer of cadmium sulfide, a semiconductor, laid on top of a sheet of silver with a layer of magnesium fluoride in the middle.
In designing the device the researchers took advantage of the chemical makeup of many explosives, particularly nitro-compounds such as DNT and its more well-known relative, TNT.
Not only do the unstable nitro groups make the chemicals more explosive, they are also characteristically electron deficient,
the researchers said. This quality increases the interaction of the molecules with natural surface defects on the semiconductor.
The device works by detecting the increased intensity in the light signal that occurs as a result of this interaction.
Potential use to sense hard-to-detect explosive"We think that higher electron deficiency of explosives leads to a stronger interaction with the semiconductor sensor"
said study co-lead author Sadao Ota, a former Ph d. student in Zhang's lab who is now an assistant professor of chemistry at the University of Tokyo.
Because of this, the researchers are hopeful that their plasmon laser sensor could detect pentaerythritol tetranitrate, or PETN, an explosive compound considered a favorite of terrorists.
Small amounts of it pack a powerful punch, and because it is plastic, it escapes x-ray machines
when not connected to detonators. It is the explosive found in Richard Reid's shoe bomb in 2001 and Umar Farouk Abdulmtallab's underwear bomb in 2009.
U s. Attorney general Eric holder Jr. was quoted recently in news reports as having"extreme extreme concern"about Yemeni bomb makers joining forces with Syrian militants to develop these hard-to-detect bombs,
which can be hidden in cell phones and mobile devices.""PETN has more nitro functional groups and is more electron deficient than the DNT we detected in our experiments,
so the sensitivity of our device should be even higher than with DNT, "said Ma.
Latest generation of plasmon sensors The sensor represents the latest milestone in surface plasmon sensor technology,
which is used now in the medical field to detect biomarkers in the early stages of disease.
The ability to increase the sensitivity of optical sensors had traditionally been restricted by the diffraction limit,
a limitation in fundamental physics that forces a tradeoff between how long and how small light can be trapped.
By coupling electromagnetic waves with surface plasmons the oscillating electrons found at the surface of metals,
researchers were able to squeeze light into nanosized spaces, but sustaining the confined energy was challenging
because light tends to dissipate at a metal's surface. The new device builds upon earlier work in plasmon lasers by Zhang's lab that compensated for this light leakage by using reflectors to bounce the surface plasmons back and forth inside the sensor similar to the way sound waves are reflected across the room
in a whispering gallery and using the optical gain from the semiconductor to amplify the light energy.
Zhang said the amplified sensor creates a much stronger signal than the passive plasmon sensors currently available
which work by detecting shifts in the wavelength of light.""The difference in intensity is similar to going from a light bulb for a table lamp to a laser pointer,
"he said.""We create a sharper signal which makes it easier to detect even smaller changes for tiny traces of explosives in the air
#Supercomputers reveal strange stress-induced transformations in world's thinnest materials (Phys. org) Interested in an ultra-fast unbreakable and flexible smart phone that recharges in a matter of seconds?
Monolayer materials may make it possible. These atom-thin sheets including the famed super material graphene feature exceptional and untapped mechanical and electronic properties.
But to fully exploit these atomically tailored wonder materials scientists must pry free the secrets of how
and break under stress. Fortunately researchers have pinpointed now the breaking mechanism of several monolayer materials hundreds of times stronger than steel with exotic properties that could revolutionize everything from armor to electronics.
A Columbia University team used supercomputers at the U s. Department of energy's Brookhaven National Laboratory to simulate
and probe quantum mechanical processes that would be extremely difficult to explore experimentally. They discovered that straining the materials induced a novel phase transition a restructuring in their near-perfect crystalline structures that leads to instability and failure.
Surprisingly the phenomenon persisted across several different materials with disparate electronic properties suggesting that monolayers may have intrinsic instabilities to be either overcome or exploited.
The results were published in the journal Physical Review B. Our calculations exposed these monolayer materials'fundamental shifts in structure
and character when stressed said study coauthor and Columbia University Ph d. candidate Eric Isaacs. To see the beautiful patterns exhibited by these materials at their breaking points for the first time was enormously exciting and important for future applications.
The team virtually examined this exotic phase transition in graphene boron nitride molybdenum disulfide and graphane all promising monolayer materials.
Monolayer materials experience strain on atomic scales demanding different investigative expertise than that of the average demolition crew.
of which can be compared directly to experimental data said Chris Marianetti a professor of materials science at Columbia University and coauthor of the study.
In this study DFT calculations revealed the materials'atomic structures stress values vibrational properties and whether they acted as metals semiconductors or insulators under strain.
Toggling between or sustaining those conductive properties are particularly important for future applications in microelectronics.
Testing all the different atomic configurations for each material under strain boils down to a tremendous amount of computation Isaacs said.
Without the highly parallel supercomputing resources and expertise at Brookhaven it would have been nearly impossible to pinpoint this transition in strained monolayers.
Everything breaks under enough stress of course but not everything meaningfully transforms along the way. A bending oak branch for example doesn't enter a strange transition phase as it creeps toward its breaking point it simply snaps.
Monolayer materials it turns out play by very different rules. Within the honeycomb-like lattices of monolayers like graphene boron nitride and graphane the atoms rapidly vibrate in place.
Different vibrational states which dictate many of the mechanical properties of the material are called modes.
As the perfect hexagonal structures of such monolayers are strained they enter a subtle soft mode the vibrating atoms slip free of their original configurations
The researchers found that this vibrational soft mode caused lingering unstable distortions in most of the known monolayer materials.
In the case of graphene boron nitride and graphane the backbone of the perfect crystalline lattice distorted toward isolated hexagonal rings.
The soft mode distortion ended up breaking graphene boron nitride and molybdenum disulfide. As the monolayers were strained the energetic cost of changing the bond lengths became significantly weaker in other words under enough stress the emergent soft mode encourages the atoms to rearrange themselves into unstable configurations.
This in turn dictates how one might control that strain and tune monolayer performance. Our work demonstrates that the soft mode failure mechanism is not unique to graphene
and suggests it might be an intrinsic feature of monolayer materials Isaacs said. Armed with this knowledge researchers may now be able to figure out how to delay the onset of the newly characterized instabilities
and improve the strength of existing monolayers. Beyond that scientists may even be able to engineer new ultra-strong materials that anticipate
and overcome the soft mode weakness. Beyond the thrill of the discovery this work is immediately useful to a large community of researchers excited to learn about
and exploit graphene and its cousins Isaacs said. For example we've been working with Columbia experimentalists who use a technique called'nanoindentation'to experimentally measure some of
what we simulated. Explore further: Engineers envision an electronic switch just three atoms thick More information:
Eric B. Isaacs and Chris A. Marianetti. Ideal strength and phonon instability of strained monolayer materials.
Phys. Rev. B 89 184111#Published 28 may 2014. journals. aps. org/prb/abstract/3/Physrevb. 89.18411 1
#An anti-glare anti-reflective display for mobile devices? If you've ever tried to watch a video on a tablet on a sunny day,
you know you have to tilt it at just the right angle to get rid of glare or invest in a special filter.
which continue to plague even the best mobile displays today. Valerio Pruneri and colleagues note that much effort has been poured into anti-reflective and anti-glare technology.
But for the most part, that hasn't included an integrated anti-glare, anti-reflective display. Users still typically have to dish out extra cash for a filter
or filmome of questionable effectivenesso lay on top of their glass screens so they can use the devices in bright light.
One of the most promising developments involves layering anti-reflective nanostructures on top of an anti-glare surface.
But the existing technique doesn't work well with glass, the material of choice for many electronic displays
so Pruneri's team at ICFO (The Institute of Photonic Sciences) in collaboration with Prantik Mazumder's team at Corning Incorporated set out to find a new method.
further research is needed to ensure that the surface can withstand heavy touchscreen use, they say.
#Self-assembling nanoparticle could improve MRI scanning for cancer diagnosis Scientists have designed a new self-assembling nanoparticle that targets tumours,
to help doctors diagnose cancer earlier. The new nanoparticle, developed by researchers at Imperial College London,
boosts the effectiveness of Magnetic resonance imaging (MRI) scanning by specifically seeking out receptors that are found in cancerous cells.
The nanoparticle is coated with a special protein, which looks for specific signals given off by tumours,
and when it finds a tumour it begins to interact with the cancerous cells. This interaction strips off the protein coating,
causing the nanoparticle to self-assemble into a much larger particle so that it is more visible on the scan.
used cancer cells and mouse models to compare the effects of the self-assembling nanoparticle in MRI scanning against commonly used imaging agents
and found that the nanoparticle produced a more powerful signal and created a clearer MRI image of the tumour.
The scientists say the nanoparticle increases the sensitivity of MRI scanning and will ultimately improve doctor's ability to detect cancerous cells at much earlier stages of development.
Professor Nicholas Long from the Department of chemistry at Imperial College London said the results show real promise for improving cancer diagnosis."By improving the sensitivity of an MRI examination
our aim is to help doctors spot something that might be cancerous much more quickly.
This would enable patients to receive effective treatment sooner, which would hopefully improve survival rates from cancer.""
""MRI SCANNERS are found in nearly every hospital up and down the country and they are used vital machines every day to scan patients'bodies
and get to the bottom of what might be wrong. But we are aware that some doctors feel that
even though MRI SCANNERS are effective at spotting large tumours, they are perhaps not as good at detecting smaller tumours in the early stages",added Professor Long.
The newly designed nanoparticle provides a tool to improve the sensitivity of MRI scanning, and the scientists are now working to enhance its effectiveness.
Professor Long said:""We would like to improve the design to make it even easier for doctors to spot a tumour
and for surgeons to then operate on it. We're now trying to add an extra optical signal
so that the nanoparticle would light up with a luminescent probe once it had found its target,
so combined with the better MRI signal it will make it even easier to identify tumours."
"Before testing and injecting the nontoxic nanoparticle into mice, the scientists had to make sure that it would not become so big
when it self-assembled that it would cause damage. They injected the nanoparticle into a saline solution inside a petri dish
and monitored its growth over a four hour period. The nanoparticle grew from 100 to 800 nanometres still small enough to not cause any harm.
The scientists are now improving the nanoparticle and hope to test their design in a human trial within the next three to five years.
Dr Juan Gallo from the Department of Surgery and Cancer at Imperial College London said:"
"We're now looking at fine tuning the size of the final nanoparticle so that it is even smaller
but still gives an enhanced MRI image. If it is too small the body will just secrete it out before imaging,
but too big and it could be harmful to the body. Getting it just right is really important before moving to a human trial. a
#Nanophotonics experts create powerful molecular sensor Nanophotonics experts at Rice university have created a unique sensor that amplifies the optical signature of molecules by about 100 billion times.
Researchers at Rice's Laboratory for Nanophotonics (LANP) said the single-molecule sensor is about 10 times more powerful that previously reported devices."
"Ours and other research groups have been designing single-molecule sensors for several years, but this new approach offers advantages over any previously reported method,
"The ideal single-molecule sensor would be able to identify an unknown moleculeven a very small oneithout any prior information about that molecule's structure or composition.
"The optical sensor uses Raman spectroscopy, a technique pioneered in the 1930s that blossomed after the advent of lasers in the 1960s.
When light strikes a molecule, most of its photons bounce off or pass directly through,
and re-emitted into another energy level that differs from their initial level. By measuring and analyzing these re-emitted photons through Raman spectroscopy,
LANP graduate student Yu Zhang used one of these, a two-coherent-laser technique called"coherent anti-Stokes Raman spectroscopy,"or CARS.
By using CARS in conjunction with a light amplifier made of four tiny gold nanodiscs,
Halas and Zhang were able to measure single molecules in a powerful new way. LANP has dubbed the new technique"surface-enhanced CARS,"or SECARS."
"The two-coherent-laser setup in SECARS is important because the second laser provides further amplification,
which contains four tiny gold discs in a precise diamond-shaped arrangement. The gap in the center of the four discs is about 15 nanometers wide.
Owing to an optical effect called a"Fano resonance, "the optical signatures of molecules caught in that gap are amplified dramatically because of the efficient light harvesting
"In previous LANP research, other geometric disc structures were used to create powerful optical processors. Zhang said the quadrumer amplifiers are a key to SECARS,
in part because they are created with standard e-beam lithographic techniques, which means they can be easily mass-produced."
"A 15-nanometer gap may sound small, but the gap in most competing devices is on the order of 1 nanometer,
"Zhang said.""Our design is much more robust because even the smallest defect in a one-nanometer device can have significant effects.
Moreover, the larger gap also results in a larger target area, the area where measurements take place.
The target area in our device is hundreds of times larger than the target area in a one-nanometer device,
"Halas, the Stanley C. Moore Professor in Electrical and Computer engineering and a professor of biomedical engineering, chemistry, physics and astronomy at Rice, said the potential applications for SECARS include chemical and biological sensing as well as metamaterials research.
and it could prove useful in experiments where existing techniques can't provide reliable data. b
#Surrey Nanosystems has super black material (Phys. org) A British company says it has scored a breakthrough in the world's darkest material.
Surrey Nanosystems describes its development as not just a black material but super-black. They are calling it Vantablack
This coating is mad e of carbon nanotubes-each 10000 times thinner than a human hair wrote Ian Johnston in The Independent on Sunday.
The manufacture of`super-black`carbon nanotube-based materials has required traditionally high temperatures preventing their direct application to sensitive electronics or materials with relatively low melting points.
which period Surrey Nanosystems successfully transferred its low-temperature manufacturing process from silicon to aluminum structures and pyroelectric sensors.
Stephen Westland professor of color science and technology at Leeds University said in The Independent These new materials they are pretty much as black as we can get almost as close to a black hole as we could imagine.
Vantablack is a major breakthrough by UK industry in the application of nanotechnology to optical instrumentation.
and long-term vibration and is suitable for coating internal components such as apertures baffles cold shields and Micro Electro Mechanical systems (MEMS)- type optical sensors.
#Researchers demonstrate novel tunable nanoantennas A research team from the University of Illinois at Urbana-Champaign has developed a novel,
tunable nanoantenna that paves the way for new kinds of plasmonic-based optomechanical systems, whereby plasmonic field enhancement can actuate mechanical motion.
Recently, there has been a lot of interest in fabricating metal-based nanotextured surfaces that are preprogrammed to alter the properties of light in a specific way after incoming light interacts with it,
an associate professor of mechanical science and engineering who led the research.""For our approach, one can take a nanoarray structure that was fabricated already and further reconfigure the plasmonic,
and hence, optical properties of select antennas. Therefore, one can decide after fabrication, rather than before,
how they want their nanostructure to modify light.""The researchers developed a novel, metal, pillar-bowtie nanoantenna (p-BNA) array template on 500-nanometer tall glass pillars (or posts.
In doing so, they demonstrated that the gap size for either individual or multiple p-BNAS can be tuned down to approx. 5 nm (approx. 4x smaller than
"On a fundamental level, our work demonstrates electron-beam based manipulation of nanoparticles an order of magnitude larger than previously possible,
using a simple SEM operating at only a fraction of the electron energies of previous work,
and computer engineering (ECE) at Illinois and was first author of the paper published in Nature Communications."
"The dramatic deformation of the nanoantennas we observe is facilitated by strong in-gap plasmonic modes excited by the passing electrons,
which give rise to nanonewton-magnitude gradient forces on the constituent metal particles.""The interdisiciplinary research teamhat included Abdul Bhuiya (MS student in ECE student), Xin Yu (ECE post-grad),
and K c. Chow (a research engineer at the Micro and Nanotechnology Laboratory) lso demonstrated that the gap size for either individual
or multiple p-BNAS can be tuned down to approximately 5 nm (roughly 4x smaller than
The team demonstrated that an electron beam from a standard scanning electron microscope (SEM) can be used to deform either individual p-BNA structures
or groups of p-BNAS within a sub-array with velocities as large as 60 nanometers per second.
A photonic crystal fiber was used to generate (quasi-white light) supercontinuum to probe the spectral response of select regions within the array.
The researchers said the importance of this work is threefold: It enables tuning of the optical (plasmonic) response of the nanoantennas, down to the level of a single nanoantenna (approximately 250 nanometers across;
it could lead to unique, spatially addressable nanophotonic devices for sensing and particle manipulation, for example;
and thermal phenomena in a nanoscale system. The team believes that the relatively high aspect ratio (pillar height-to-thickness) of 4. 2 for the p-BNAS,
Based on the observed experiments, the gradient force is estimated to be on the order of nanonewtons.""Our fabrication process shows for the first time an innovative way of fabricating plasmonic nanoantenna structures under the SEM,
which avoids complications such as proximity effects from conventional lithography techniques, "Bhuiya said.""This process also reduces the gap of the nanoantennas down to 5 nm under SEM with a controlled reduction rate.
With this new fabrication technique, it opens an avenue to study different phenomena which leads to new exciting research fields. e
#Sand-based lithium ion batteries that outperform standard by three times (Phys. org) esearchers at the University of California, Riverside's Bourns College of Engineering have created a lithium ion battery that outperforms the current industry standard by three times.
environmentally friendly way to produce high performance lithium ion battery anodes,"said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.
and saw it was made up primarily of quartz, or silicon dioxide. His research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles.
He is focused on the anode or negative side of the battery. Graphite is the current standard material for the anode,
but as electronics have become more powerful graphite's ability to be improved has been tapped virtually out.
Researchers are focused now on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite.
The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.
Favors set out to solve both these problems. He researched sand to find a spot in the United states where it is found with a high percentage of quartz.
That took him to the Cedar Creek Reservoir east of Dallas, where he grew up.
Sand in hand, he came back to the lab at UC Riverside and milled it down to the nanometer scale,
followed by a series of purification steps changing its color from brown to bright white, similar in color and texture to powdered sugar.
After that, he ground salt and magnesium, both very common elements found dissolved in sea water into the purified quartz.
The resulting powder was heated then. With the salt acting as a heat absorber, the magnesium worked to remove the oxygen from the quartz,
resulting in pure silicon. The Ozkan team was pleased with how the process went. And they also encountered an added positive surprise.
The pure nano-silicon formed in a very porous 3-D silicon sponge like consistency.
That porosity has proved to be the key to improving the performance of the batteries built with the nano-silicon l
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