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  • richardmitnick 10:57 am on May 18, 2020 Permalink | Reply
    Tags: "A theoretical boost to nano-scale devices", , Nanotechnology, , The Korea Advanced Institute of Science and Technology (KAIST)   

    From The Korea Advanced Institute of Science and Technology (KAIST) via phys.org: “A theoretical boost to nano-scale devices” 

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    From The Korea Advanced Institute of Science and Technology (KAIST)

    via


    From phys.org

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    The newly developed formalism and QFL splitting analysis led to new ways of characterizing extremely scaled-down semiconductor devices and the technology computer-aided design (TCAD) of next- generation nano-electronic/energy/bio devices. Credit: Yong-Hoon Kim, KAIST

    Semiconductor companies are struggling to develop devices that are mere nanometers in size, and much of the challenge lies in being able to more accurately describe the underlying physics at that nano-scale. But a new computational approach that has been in the works for a decade could break down these barriers.

    Devices using semiconductors, from computers to solar cells, have enjoyed tremendous efficiency improvements in the last few decades. Famously, one of the co-founders of Intel, Gordon Moore, observed that the number of transistors in an integrated circuit doubles about every two years—and this ‘Moore’s law’ held true for some time.

    In recent years, however, such gains have slowed as firms that attempt to engineer nano-scale transistors hit the limits of miniaturization at the atomic level.

    Researchers with the School of Electrical Engineering at KAIST have developed a new approach to the underlying physics of semiconductors.

    “With open quantum systems as the main research target of our lab, we were revisiting concepts that had been taken for granted and even appear in standard semiconductor physics textbooks such as the voltage drop in operating semiconductor devices,” said the lead researcher Professor Yong-Hoon Kim. “Questioning how all these concepts could be understood and possibly revised at the nano-scale, it was clear that there was something incomplete about our current understanding.”

    “And as the semiconductor chips are being scaled down to the atomic level, coming up with a better theory to describe semiconductor devices has become an urgent task.”

    The current understanding states that semiconductors are materials that act like half-way houses between conductors, like copper or steel, and insulators, like rubber or Styrofoam. They sometimes conduct electricity, but not always. This makes them a great material for intentionally controlling the flow of current, which in turn is useful for constructing the simple on/off switches—transistors—that are the foundation of memory and logic devices in computers.

    In order to ‘switch on’ a semiconductor, a current or light source is applied, exciting an electron in an atom to jump from what is called a ‘valence band,’ which is filled with electrons, up to the ‘conduction band,’ which is originally unfilled or only partially filled with electrons. Electrons that have jumped up to the conduction band thanks to external stimuli and the remaining ‘holes’ are now able to move about and act as charge carriers to flow electric current.

    The physical concept that describes the populations of the electrons in the conduction band and the holes in the valence band and the energy required to make this jump is formulated in terms of the so-called ‘Fermi level.’ For example, you need to know the Fermi levels of the electrons and holes in order to know what amount of energy you are going to get out of a solar cell, including losses.

    But the Fermi level concept is only straightforwardly defined so long as a semiconductor device is at equilibrium—sitting on a shelf doing nothing—and the whole point of semiconductor devices is not to leave them on the shelf.

    Some 70 years ago, William Shockley, the Nobel Prize-winning co-inventor of the transistor at the Bell Labs, came up with a bit of a theoretical fudge, the ‘quasi-Fermi level,’ or QFL, enabling rough prediction and measurement of the interaction between valence band holes and conduction band electrons, and this has worked pretty well until now.

    “But when you are working at the scale of just a few nanometers, the methods to theoretically calculate or experimentally measure the splitting of QFLs were just not available,” said Professor Kim.

    This means that at this scale, issues such as errors relating to voltage drop take on much greater significance.

    Kim’s team worked for nearly ten years on developing a novel theoretical description of nano-scale quantum electron transport that can replace the standard method—and the software that allows them to put it to use. This involved the further development of a bit of math known as the Density Functional Theory that simplifies the equations describing the interactions of electrons, and which has been very useful in other fields such as high-throughput computational materials discovery.

    For the first time, they were able to calculate the QFL splitting, offering a new understanding of the relationship between voltage drop and quantum electron transport in atomic scale devices.

    In addition to looking into various interesting non-equilibrium quantum phenomena with their novel methodology, the team is now further developing their software into a computer-aided design tool to be used by semiconductor companies for developing and fabricating advanced semiconductor devices.

    Science paper:
    https://www.pnas.org/content/117/19/10142
    PNAS

    See the full article here .

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    About Science X in 100 words
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  • richardmitnick 10:04 am on May 9, 2020 Permalink | Reply
    Tags: "New imaging technology allows visualization of nanoscale structures inside whole cells and tissues", , , , , Nanotechnology,   

    From Purdue University: “New imaging technology allows visualization of nanoscale structures inside whole cells and tissues” 

    From Purdue University

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    This image shows a 3D super-resolution reconstruction of dendrites in primary visual cortex. (Image provided)

    Since Robert Hooke’s first description of a cell in Micrographia 350 years ago, microscopy has played an important role in understanding the rules of life.

    However, the smallest resolvable feature, the resolution, is restricted by the wave nature of light. This century-old barrier has restricted understanding of cellular functions, interactions and dynamics, particularly at the sub-micron to nanometer scale.

    Super-resolution fluorescence microscopy overcomes this fundamental limit, offering up to tenfold improvement in resolution, and allows scientists to visualize the inner workings of cells and biomolecules at unprecedented spatial resolution.

    Such resolving capability is impeded, however, when observing inside whole-cell or tissue specimens, such as the ones often analyzed during the studies of the cancer or the brain. Light signals, emitted from molecules inside a specimen, travel through different parts of cell or tissue structures at different speeds and result in aberrations, which will deteriorate the image.

    Now, Purdue University researchers have developed a new technology to overcome this challenge.

    “Our technology allows us to measure wavefront distortions induced by the specimen, either a cell or a tissue, directly from the signals generated by single molecules – tiny light sources attached to the cellular structures of interest,” said Fang Huang, an assistant professor of biomedical engineering in Purdue’s College of Engineering. “By knowing the distortion induced, we can pinpoint the positions of individual molecules at high precision and accuracy. We obtain thousands to millions of coordinates of individual molecules within a cell or tissue volume and use these coordinates to reveal the nanoscale architectures of specimen constituents.”

    The Purdue team’s technology is recently published in Nature Methods. A video showing an animated 3D super-resolution is available at https://youtu.be/c9j621vUFBM. This tool from Purdue researchers allows visualization of nanoscale structures inside whole cells and tissues. It could allow for better understanding for diseases affecting the brain and regenerative therapies.

    “During three-dimensional super-resolution imaging, we record thousands to millions of emission patterns of single fluorescent molecules,” said Fan Xu, a postdoctoral associate in Huang’s lab and a co-first author of the publication. “These emission patterns can be regarded as random observations at various axial positions sampled from the underlying 3D point-spread function describing the shapes of these emission patterns at different depths, which we aim to retrieve. Our technology uses two steps: assignment and update, to iteratively retrieve the wavefront distortion and the 3D responses from the recorded single molecule dataset containing emission patterns of molecules at arbitrary locations.”

    The Purdue technology allows finding the positions of biomolecules with a precision down to a few nanometers inside whole cells and tissues and therefore, resolving cellular and tissue architectures with high resolution and fidelity.

    “This advancement expands the routine applicability of super-resolution microscopy from selected cellular targets near coverslips to intra- and extra-cellular targets deep inside tissues,” said Donghan Ma, a postdoctoral researcher in Huang’s lab and a co-first author of the publication. “This newfound capacity of visualization could allow for better understanding for neurodegenerative diseases such as Alzheimer’s, and many other diseases affecting the brain and various parts inside the body.”

    The National Institutes of Health provided major support for the research.

    Other members of the research team include Gary Landreth, a professor from Indiana University’s School of Medicine; Sarah Calve, an associate professor of biomedical engineering in Purdue’s College of Engineering (currently an associate professor of mechanical engineering at the University of Colorado Boulder); Peng Yin, a professor from Harvard Medical School; and Alexander Chubykin, an assistant professor of biological sciences at Purdue. The complete list of authors can be found in Nature Methods.

    “This technical advancement is startling and will fundamentally change the precision with which we evaluate the pathological features of Alzheimer’s disease,” Landreth said. “We are able to see smaller and smaller objects and their interactions with each other, which helps reveal structure complexities we have not appreciated before.”

    Calve said the technology is a step forward in regenerative therapies to help promote repair within the body.

    “This development is critical for understanding tissue biology and being able to visualize structural changes,” Calve said.

    Chubykin, whose lab focuses on autism and diseases affecting the brain, said the high-resolution imaging technology provides a new method for understanding impairments in the brain.

    “This is a tremendous breakthrough in terms of functional and structural analyses,” Chubykin said. “We can see a much more detailed view of the brain and even mark specific neurons with genetic tools for further study.”

    The team worked with the Purdue Research Foundation Office of Technology Commercialization to patent the technology. The office recently moved into the Convergence Center for Innovation and Collaboration in Discovery Park District, adjacent to the Purdue campus.

    The inventors are looking for partners to commercialize their technology. For more information on licensing this innovation, contact Dipak Narula of OTC at dnarula@prf.org.

    See the full article here .

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    Purdue University is a public research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science, technology, and agriculture in his name. The first classes were held on September 16, 1874, with six instructors and 39 students.

    The main campus in West Lafayette offers more than 200 majors for undergraduates, over 69 masters and doctoral programs, and professional degrees in pharmacy and veterinary medicine. In addition, Purdue has 18 intercollegiate sports teams and more than 900 student organizations. Purdue is a member of the Big Ten Conference and enrolls the second largest student body of any university in Indiana, as well as the fourth largest foreign student population of any university in the United States.

     
  • richardmitnick 12:33 pm on May 8, 2020 Permalink | Reply
    Tags: "Scanning with golden bow ties", , , , , Nanotechnology, Terahertz scanners   

    From COSMOS: “Scanning with golden bow ties” 

    Cosmos Magazine bloc

    From COSMOS

    08 May 2020
    Phil Dooley

    Detectors would operate in terahertz region.

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    Credits: DIMITAR JEVTICS

    Australian and British physicists have unveiled their design for a high-precision detector they say could enable a new generation of safe compact scanners.

    As described in a paper in the journal Science, it is based around tiny “bow ties”, each comprising two triangles of solid gold connected by two nanowires.

    This design allows it to operate in the terahertz region of the electromagnetic spectrum, between microwaves and infrared. Terahertz scanning offers a safer low-energy alternative to X-rays: it is not powerful enough to ionise materials.

    However, it still penetrates materials such as plastics, wood and paper, is absorbed by water, and is reflected by metals, giving the technology the capability to analyse a wide range of samples.

    The bow ties also are able to detect the polarisation of the terahertz radiation, which adds another dimension to the detector’s versatility.

    “The polarisation gives you much more useful information, especially about biological molecules, for example their chirality,” says Chennupati Jagadish from the Australian National University (ANU).

    “Complex molecules have their own terahertz fingerprints, so this technology can be used for finding cancer biomarkers, locating explosives or measuring moisture levels in crops.”

    The device is the result of a collaboration between ANU and Oxford University in England and Scotland’s Strathclyde University.

    Importantly, the researchers say, it overcomes a limitation in the resolution, or detail, of conventional terahertz imaging, which is linked to its millimetre-scale wavelength – a million times larger than X-rays, with nanometre-scale wavelengths.

    The design gets around this limitation with the microscopic scale of the bow ties. The pair of nanowires at their heart are indium phosphide wires one hundredth the size of a human hair: around 280 nanometres in diameter and ten micrometres long.

    Although each detector is much smaller than the terahertz waves (around 300 microns), an array of bow ties can be used to create a near-field image that bypasses the diffraction limit of the terahertz radiation’s wavelength.

    To detect the polarisation of the radiation, the team combined two bow ties, set at right angles to each other, with their central nanowires crossing but not in contact – one bow tie is set slightly above the other.

    Although a simplistic-sounding design, the vertically offset configuration took three years of collaboration to devise and manufacture.

    The nanowires were created at ANU, the triangles were added at Oxford as antennae to boost the signal level (gold being the obvious choice due to its high conductivity), then the devices were assembled at Strathclyde.

    The team is now developing nano-scale electronics to connect to the detector, so the whole device can be built onto a single chip, in contrast with existing bulky terahertz scanners.

    See the full article here .


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  • richardmitnick 4:17 pm on April 24, 2020 Permalink | Reply
    Tags: "Maryland Engineers Open Door to Big New Library of Tiny Nanoparticles", A James Clark School of Engineering, , , Nanotechnology, ,   

    From University of Maryland: “Maryland Engineers Open Door to Big New Library of Tiny Nanoparticles” 


    From University of Maryland

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    April 24, 2020

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    The development of bimetallic nanoparticles (i.e., tiny particles composed of two different metals that exhibit several new and improved properties) represents a novel area of research with a wide range of potential applications. Now, a research team in the University of Maryland (UMD)’s Department of Materials Science and Engineering (MSE) has developed a new method for mixing metals generally known to be immiscible, or unmixable, at the nanoscale to create a new range of bimetallic materials. Such a library will be useful for studying the role of these bimetallic particles in various reaction scenarios such as the transformation of carbon dioxide to fuel and chemicals.

    The study, led by MSE Professor Liangbing Hu, was published in Science Advances on April 24, 2020. Chunpeng Yang, an MSE Research Associate, served as first author on the study.

    “With this method, we can quickly develop different bimetallics using various elements, but with the same structure and morphology,” said Hu. “Then we can use them to screen catalytic materials for a reaction; such materials will not be limited by synthesizing difficulties.”

    The complex nature of nanostructured bimetallic particles makes mixing such particles difficult, for a variety of reasons—including the chemical makeup of the metals, particle size, and how metals arrange themselves at the nanoscale—using conventional methods.

    This new non-equilibrium synthesis method exposes copper-based mixes to a thermal shock of approximately 1300 ̊ Celsius for .02 seconds and then rapidly cools them to room temperature. The goal of using such a short interval of thermal heat is to quickly trap, or ‘freeze,’ the high-temperature metal atoms at room temperature while maintaining their mixing state. In doing so, the research team was able to prepare a collection of homogeneous copper-based alloys. Typically, copper only mixes with a few other metals, such as zinc and palladium—but by using this new method, the team broadened the miscible range to include copper with nickel, iron, and silver, as well.

    “Using a scanning electron microscope (SEM) and transmission electron microscope (TEM), we were able to confirm the morphology – how the materials formed – and size of the resulting Cu-Ag [copper-silver] bimetallic nanoparticles,” Yang said.

    This method will enable scientists to create more diverse nanoparticle systems, structures, and materials having applications in catalysis, biological applications, optical applications, and magnetic materials.

    As a model system for rapid catalyst development, the team investigated copper-based alloys as catalysts for carbon monoxide reduction reactions, in collaboration with Feng Jiao, a professor in the Department of Chemical and Biomolecular Engineering at the University of Delaware. The electro-catalysis of carbon monoxide reduction (COR) is an attractive platform, allowing scientists to use greenhouse gas and renewable electrical energy to produce fuels and chemicals.

    “Copper is, thus far, the most promising monometallic electrocatalyst that drives carbon monoxide reduction to value-added chemicals,” said Jiao. “The ability to rapidly synthesize a wide variety of copper-based bimetallic nanoalloys with a uniform structure enables us to conduct fundamental studies on the structure-property relationship in COR and other catalyst systems.”

    This non-equilibrium synthetic strategy can be extended to other bimetallic or metal oxide systems, too. Utilizing artificial intelligence-based machine learning, the method will make rapid catalyst screening and rational design possible.

    See the full article here .

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    U Maryland Campus

    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 11:11 am on April 13, 2020 Permalink | Reply
    Tags: "Team designs carbon nanostructure stronger than diamonds", , , Nanotechnology, , ,   

    From UC Irvine via phys.org: “Team designs carbon nanostructure stronger than diamonds” 

    UC Irvine bloc

    From UC Irvine

    via


    phys.org

    April 13, 2020
    Brian Bell

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    With wall thicknesses of about 160 nanometers, a closed-cell, plate-based nanolattice structure designed by researchers at UCI and other institutions is the first experimental verification that such arrangements reach the theorized limits of strength and stiffness in porous materials. Credit: Cameron Crook and Jens Bauer / UCI

    Researchers at the University of California, Irvine and other institutions have architecturally designed plate-nanolattices—nanometer-sized carbon structures—that are stronger than diamonds as a ratio of strength to density.

    In a recent study in Nature Communications, the scientists report success in conceptualizing and fabricating the material, which consists of closely connected, closed-cell plates instead of the cylindrical trusses common in such structures over the past few decades.

    “Previous beam-based designs, while of great interest, had not been so efficient in terms of mechanical properties,” said corresponding author Jens Bauer, a UCI researcher in mechanical & aerospace engineering. “This new class of plate-nanolattices that we’ve created is dramatically stronger and stiffer than the best beam-nanolattices.”

    According to the paper, the team’s design has been shown to improve on the average performance of cylindrical beam-based architectures by up to 639 percent in strength and 522 percent in rigidity.

    Members of the architected materials laboratory of Lorenzo Valdevit, UCI professor of materials science & engineering as well as mechanical & aerospace engineering, verified their findings using a scanning electron microscope and other technologies provided by the Irvine Materials Research Institute.

    “Scientists have predicted that nanolattices arranged in a plate-based design would be incredibly strong,” said lead author Cameron Crook, a UCI graduate student in materials science & engineering. “But the difficulty in manufacturing structures this way meant that the theory was never proven, until we succeeded in doing it.”

    Bauer said the team’s achievement rests on a complex 3-D laser printing process called two-photon lithography direct laser writing. As an ultraviolet-light-sensitive resin is added layer by layer, the material becomes a solid polymer at points where two photons meet. The technique is able to render repeating cells that become plates with faces as thin as 160 nanometers.

    Bauer said the team’s achievement rests on a complex 3-D laser printing process called two-photon polymerization direct laser writing. As a laser is focused inside a droplet of an ultraviolet-light-sensitive liquid resin, the material becomes a solid polymer where molecules are simultaneously hit by two photons. By scanning the laser or moving the stage in three dimensions, the technique is able to render periodic arrangements of cells, each consisting of assemblies of plates as thin as 160 nanometers.

    One of the group’s innovations was to include tiny holes in the plates that could be used to remove excess resin from the finished material. As a final step, the lattices go through pyrolysis, in which they’re heated to 900 degrees Celsius in a vacuum for one hour. According to Bauer, the end result is a cube-shaped lattice of glassy carbon that has the highest strength scientists ever thought possible for such a porous material.

    Bauer said that another goal and accomplishment of the study was to exploit the innate mechanical effects of the base substances. “As you take any piece of material and dramatically decrease its size down to 100 nanometers, it approaches a theoretical crystal with no pores or cracks. Reducing these flaws increases the system’s overall strength,” he said.

    “Nobody has ever made these structures independent from scale before,” added Valdevit, who directs UCI’s Institute for Design and Manufacturing Innovation. “We were the first group to experimentally validate that they could perform as well as predicted while also demonstrating an architected material of unprecedented mechanical strength.”

    Nanolattices hold great promise for structural engineers, particularly in aerospace, because it’s hoped that their combination of strength and low mass density will greatly enhance aircraft and spacecraft performance.

    Other co-authors on the study were Anna Guell Izard, a UCI graduate student in mechanical & aerospace engineering, and researchers from UC Santa Barbara and Germany’s Martin Luther University of Halle-Wittenberg. The project was funded by the Office of Naval Research and the German Research Foundation.

    See the full article here .

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    UC Irvine Campus

    Since 1965, the University of California, Irvine has combined the strengths of a major research university with the bounty of an incomparable Southern California location. UCI’s unyielding commitment to rigorous academics, cutting-edge research, and leadership and character development makes the campus a driving force for innovation and discovery that serves our local, national and global communities in many ways.

    With more than 29,000 undergraduate and graduate students, 1,100 faculty and 9,400 staff, UCI is among the most dynamic campuses in the University of California system. Increasingly a first-choice campus for students, UCI ranks among the top 10 U.S. universities in the number of undergraduate applications and continues to admit freshmen with highly competitive academic profiles.

    UCI fosters the rigorous expansion and creation of knowledge through quality education. Graduates are equipped with the tools of analysis, expression and cultural understanding necessary for leadership in today’s world.

    Consistently ranked among the nation’s best universities – public and private – UCI excels in a broad range of fields, garnering national recognition for many schools, departments and programs. Times Higher Education ranked UCI No. 1 among universities in the U.S. under 50 years old. Three UCI researchers have won Nobel Prizes – two in chemistry and one in physics.

    The university is noted for its top-rated research and graduate programs, extensive commitment to undergraduate education, and growing number of professional schools and programs of academic and social significance. Recent additions include highly successful programs in public health, pharmaceutical sciences and nursing science; an expanding education school; and a law school already ranked among the nation’s top 10 for its scholarly impact.

     
  • richardmitnick 12:59 pm on March 11, 2020 Permalink | Reply
    Tags: , , , , Nanotechnology, , ,   

    From MIT News: “Novel method for easier scaling of quantum devices” 

    MIT News

    From MIT News

    March 5, 2020
    Rob Matheson

    1
    An MIT team found a way to “recruit” normally disruptive quantum bits (qubits) in diamond to, instead, help carry out quantum operations. This approach could be used to help scale up quantum computing systems. Image: Christine Daniloff, MIT.

    System “recruits” defects that usually cause disruptions, using them to instead carry out quantum operations.

    In an advance that may help researchers scale up quantum devices, an MIT team has developed a method to “recruit” neighboring quantum bits made of nanoscale defects in diamond, so that instead of causing disruptions they help carry out quantum operations.

    Quantum devices perform operations using quantum bits, called “qubits,” that can represent the two states corresponding to classic binary bits — a 0 or 1 — or a “quantum superposition” of both states simultaneously. The unique superposition state can enable quantum computers to solve problems that are practically impossible for classical computers, potentially spurring breakthroughs in biosensing, neuroimaging, machine learning, and other applications.

    One promising qubit candidate is a defect in diamond, called a nitrogen-vacancy (NV) center, which holds electrons that can be manipulated by light and microwaves. In response, the defect emits photons that can carry quantum information. Because of their solid-state environments, however, NV centers are always surrounded by many other unknown defects with different spin properties, called “spin defects.” When the measurable NV-center qubit interacts with those spin defects, the qubit loses its coherent quantum state — “decoheres”— and operations fall apart. Traditional solutions try to identify these disrupting defects to protect the qubit from them.

    In a paper published Feb. 25 in Physical Review Letters, the researchers describe a method that uses an NV center to probe its environment and uncover the existence of several nearby spin defects. Then, the researchers can pinpoint the defects’ locations and control them to achieve a coherent quantum state — essentially leveraging them as additional qubits.

    In experiments, the team generated and detected quantum coherence among three electronic spins — scaling up the size of the quantum system from a single qubit (the NV center) to three qubits (adding two nearby spin defects). The findings demonstrate a step forward in scaling up quantum devices using NV centers, the researchers say.

    “You always have unknown spin defects in the environment that interact with an NV center. We say, ‘Let’s not ignore these spin defects, which [if left alone] could cause faster decoherence. Let’s learn about them, characterize their spins, learn to control them, and ‘recruit’ them to be part of the quantum system,’” says the lead co-author Won Kyu Calvin Sun, a graduate student in the Department of Nuclear Science and Engineering and a member of the Quantum Engineering group. “Then, instead of using a single NV center [or just] one qubit, we can then use two, three, or four qubits.”

    Joining Sun on the paper are lead author Alexandre Cooper ’16 of Caltech; Jean-Christophe Jaskula, a research scientist in the MIT Research Laboratory of Electronics (RLE) and member of the Quantum Engineering group at MIT; and Paola Cappellaro, a professor in the Department of Nuclear Science and Engineering, a member of RLE, and head of the Quantum Engineering group at MIT.

    Characterizing defects

    NV centers occur where carbon atoms in two adjacent places in a diamond’s lattice structure are missing — one atom is replaced by a nitrogen atom, and the other space is an empty “vacancy.” The NV center essentially functions as an atom, with a nucleus and surrounding electrons that are extremely sensitive to tiny variations in surrounding electrical, magnetic, and optical fields. Sweeping microwaves across the center, for instance, makes it change, and thus control, the spin states of the nucleus and electrons.

    Spins are measured using a type of magnetic resonance spectroscopy. This method plots the frequencies of electron and nucleus spins in megahertz as a “resonance spectrum” that can dip and spike, like a heart monitor. Spins of an NV center under certain conditions are well-known. But the surrounding spin defects are unknown and difficult to characterize.

    In their work, the researchers identified, located, and controlled two electron-nuclear spin defects near an NV center. They first sent microwave pulses at specific frequencies to control the NV center. Simultaneously, they pulse another microwave that probes the surrounding environment for other spins. They then observed the resonance spectrum of the spin defects interacting with the NV center.

    The spectrum dipped in several spots when the probing pulse interacted with nearby electron-nuclear spins, indicating their presence. The researchers then swept a magnetic field across the area at different orientations. For each orientation, the defect would “spin” at different energies, causing different dips in the spectrum. Basically, this allowed them to measure each defect’s spin in relation to each magnetic orientation. They then plugged the energy measurements into a model equation with unknown parameters. This equation is used to describe the quantum interactions of an electron-nuclear spin defect under a magnetic field. Then, they could solve the equation to successfully characterize each defect.

    Locating and controlling

    After characterizing the defects, the next step was to characterize the interaction between the defects and the NV, which would simultaneously pinpoint their locations. To do so, they again swept the magnetic field at different orientations, but this time looked for changes in energies describing the interactions between the two defects and the NV center. The stronger the interaction, the closer they were to one another. They then used those interaction strengths to determine where the defects were located, in relation to the NV center and to each other. That generated a good map of the locations of all three defects in the diamond.

    Characterizing the defects and their interaction with the NV center allow for full control, which involves a few more steps to demonstrate. First, they pump the NV center and surrounding environment with a sequence of pulses of green light and microwaves that help put the three qubits in a well-known quantum state. Then, they use another sequence of pulses that ideally entangles the three qubits briefly, and then disentangles them, which enables them to detect the three-spin coherence of the qubits.

    The researchers verified the three-spin coherence by measuring a major spike in the resonance spectrum. The measurement of the spike recorded was essentially the sum of the frequencies of the three qubits. If the three qubits for instance had little or no entanglement, there would have been four separate spikes of smaller height.

    “We come into a black box [environment with each NV center]. But when we probe the NV environment, we start seeing dips and wonder which types of spins give us those dips. Once we [figure out] the spin of the unknown defects, and their interactions with the NV center, we can start controlling their coherence,” Sun says. “Then, we have full universal control of our quantum system.”

    Next, the researchers hope to better understand other environmental noise surrounding qubits. That will help them develop more robust error-correcting codes for quantum circuits. Furthermore, because on average the process of NV center creation in diamond creates numerous other spin defects, the researchers say they could potentially scale up the system to control even more qubits. “It gets more complex with scale. But if we can start finding NV centers with more resonance spikes, you can imagine starting to control larger and larger quantum systems,” Sun says.

    See the full article here .


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    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

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  • richardmitnick 12:13 pm on March 5, 2020 Permalink | Reply
    Tags: "Microstructures Self-Assemble into New Materials", A team of engineers at Caltech and ETH Zürich have developed a material that is designed at the nanoscale but assembles itself—with no need for the precision laser assembly., , , , , Nanoarchitected material at the cubic-centimeter scale., Nanotechnology   

    From Caltech: “Microstructures Self-Assemble into New Materials” 

    Caltech Logo

    From Caltech

    March 02, 2020
    Robert Perkins
    (626) 395‑1862
    rperkins@caltech.edu

    1
    Caltech

    A new process developed at Caltech makes it possible for the first time to manufacture large quantities of materials whose structure is designed at a nanometer scale—the size of DNA’s double helix.

    Pioneered by Caltech materials scientist Julia R. Greer, “nanoarchitected materials” exhibit unusual, often surprising properties—for example, exceptionally lightweight ceramics that spring back to their original shape, like a sponge, after being compressed. These properties could be desirable for applications ranging from ultrasensitive tactile sensors to advanced batteries, but so far, engineers have only been able to create them in very limited amounts. To create a material whose structure is designed at such a small scale, they often have to be assembled nano-layer by nano-layer in a 3-D printing process that uses a high-precision laser and custom-synthesized chemicals. That painstaking process limits the overall amount of material that can be built.

    Now, a team of engineers at Caltech and ETH Zürich have developed a material that is designed at the nanoscale but assembles itself—with no need for the precision laser assembly. For the first time, they were able to create a sample of nanoarchitected material at the cubic-centimeter scale.

    “We couldn’t 3-D print this much nanoarchitected material even in a month; instead we’re able to grow it in a matter of hours,” says Carlos Portela, postdoctoral scholar at Caltech and lead author of a study on the new process that was published by the journal Proceedings of the National Academy of Sciences (PNAS) on March 2.

    At the nanoscale, the material looks like a sponge but is actually an assembly of interconnected curved shells. That’s the key to the material’s high stiffness- and strength-to-weight ratios: the smoothly curved thin shells, like those of an egg, are free of corners or junctions, which are usually weak points leading to failure in other similar materials. This provides unique mechanical benefits with a minimum of material actually used. In testing, a sample of the material was able to achieve strength-to-density ratios comparable to some forms of steel, while thinner-walled configurations exhibit negligible damage and recovery after repeated compression.

    “This new fabrication route, supported by the experimental and numerical analysis that we’ve conducted, gets us one step closer to being able to produce nanoarchitected materials at a useful scale, with a marked ease of fabrication,” says Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics, and Medical Engineering and coauthor of the PNAS paper.

    Though it is measurably more resilient than virtually all nanoarchitected materials with similar densities synthesized by the Greer group, what makes these so-called nano-labyrinthine materials particularly special is that they assemble themselves. This achievement, led by Caltech graduate student Daryl Yee, works like this: two materials that don’t dissolve into each other are mixed together, blending them to create a disordered state. Heating up the mixture polymerizes the materials so that the current geometry gets locked in place. One of the two materials is then removed, leaving nanoscale shells. The resulting porous template is subsequently coated, and then the second polymer is removed. What’s left is lightweight nano-shell network.

    The process requires extreme precision; if incorrectly heated, the microstructure will either melt together or collapse and will not lead to interconnected shells. But for the first time, the team sees the potential to scale up nanoarchitecture.

    “It is exciting to see our computationally designed optimal nanoscale architectures being realized experimentally in the lab,” says Dennis M. Kochmann, corresponding author of the PNAS paper and professor of mechanics and materials at ETH Zürich and a visiting associate in aerospace at Caltech. His team, including former Caltech graduate student A. Vidyasagar and Sebastian Krödel and Tamara Weissenbach of ETH Zürich, predicted the versatile properties of the nano-labyrinthine materials through theory and simulations.

    Next, the team plans to expand the tunability and versatility of the process by exploring pathways to carefully control the microstructure, expand on the material options for the nano-shells, and push for the production of larger volumes of the material.

    See the full article here .


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    Please help promote STEM in your local schools.


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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 7:44 pm on March 4, 2020 Permalink | Reply
    Tags: "Nanoscale spectroscopy review showcases a bright future", , Luminescent nanoparticles, Nanotechnology, , Rapid progress in optical microscopy that made it possible to 'see' the fluorescence of single photons and thereby the discovery of the underlying photophysics of the nanoscale.,   

    From University of Technology Sidney via phys.org: “Nanoscale spectroscopy review showcases a bright future” 

    From University of Technology, Sidney

    via


    phys.org

    1
    People enjoy using smartphones and touch screens to send messages, and high resolution screen displays to view images and watch videos but they might forget this technology comes from years of fundamental scientific research into how things work at the smallest of scales. Credit: Luco Bravo Unsplash.

    Modern society is working closer to the nanoscale than it realises. Breakthroughs and advances in developing and manipulating nanostructures have led to technological progress that not only drives imaging and sensing devices but also makes possible mainstays of modern life such as touch screens and high resolution LED displays.

    A new review authored by international leaders in their field, and published in Nature, focuses on the luminescent nanoparticles at the heart of many advances and the opportunities and challenges for these technologies to reach their full potential.

    Senior author, Professor Dayong Jin, says that by trying to understand how single nanoparticles behave scientists are asking very fundamental questions to develop tools that can be used to realise technological breakthroughs in diverse areas including personalised medicine, cyber security and quantum communication.

    “The purpose of this field is to really understand the properties of these artificial atoms so that their properties can be controlled and tailored for the application we need,” he says. Professor Jin is the Director of the University of Technology Sydney (UTS) Institute for Biomedical Materials & Devices (IBMD) and director of UTS-SUStech Joint Research Centre for Biomedical Materials & Devices.

    The paper charts the rise of single molecule measurements and the rapid progress in optical microscopy that made it possible to ‘see’ the fluorescence of single photons and, thereby, the discovery of the underlying photophysics of the nanoscale. From quantum dots to carbon dots, fluorescent nanodiamonds and nanoparticles fabricated from obscure minerals such as perovskite—all promising tools for applications as diverse as imaging, biomarker detection and data storage.

    But as the authors admit “the closer we pursue the perfection in nanoparticle design, the harder the challenges become”.

    Lead author Dr. Jiajia Zhou from UTS IBMD, who specialises in building single particle optical spectroscopy to uncover the more unpredictable behaviour of nanoparticles, says that there is demand for smaller and more efficient nanoparticles with new desirable functions and characteristics.

    “Especially for biomedical and intracellular applications such as molecular probes and sensors. Here we are talking about only a few nanometers in size where the challenge in forming uniform nanoparticles and controlling their shape, size and optical properties requires new knowledge about nanoparticle surface chemistry, for example,” she says.

    Still, in a very fast moving field the potential seems only to be limited by scientific imagination and, more likely, the ability of scientific and engineering disciplines to integrate knowledge and skills, the authors say.

    “This paper is a large survey and highlights the need for a global effort and resources towards the fundamental research needed to keep pushing the boundaries of what is possible at the nanoscale, so society can benefit from the many emerging opportunities,” Professor Jin says.

    Professor Jin imagines a world where nanoscale tweezing is used to assemble hybrid nanoparticle- based devices and where biomedical signatures can be used to answer questions around an individual’s response to drug therapies, all from one drop of blood.

    “Everyday when people enjoy using smartphones and touch screens to send messages, and high resolution screen displays to view images and watch videos, they might forget where this technology comes from.

    “These technologies may look like engineering projects but really they are the result of decades of research from scientists and students working ‘in the dark’ to answer fundamental questions about how nature works at the smallest of scales,” he said.

    See the full article here .

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    Please help promote STEM in your local schools.

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    UTS is a public university of technology defined by our support for the economic, social and cultural prosperity of our communities. We are measured by the success of our students, staff and partners and committed to research, innovation and the dissemination of knowledge of public value. We are, and always will be, an inclusive university.

    UTS has a culturally diverse campus life and vibrant international exchange study and research programs that prepare graduates for the workplaces of today and the future. Our campus is in the heart of Sydney’s creative and digital precinct and alongside Sydney’s central business district. Continuing a 10-year period of major development, the ongoing transformation of the UTS campus will ensure we continue to maintain and develop a purpose- and sustainably-built campus to support innovation in education and research.

     
  • richardmitnick 10:25 am on February 24, 2020 Permalink | Reply
    Tags: "Helix of an Elusive Rare Earth Metal Could Help Push Moore's Law to The Next Level", , , Nanotechnology, , Rare earth metal Tellurium, , , The tellurium helix slip neatly inside a nanotube of boron nitride., Transistors   

    From Purdue University via Science Alert: “Helix of an Elusive Rare Earth Metal Could Help Push Moore’s Law to The Next Level” 

    From Purdue University

    via

    ScienceAlert

    Science Alert

    23 FEB 2020
    MIKE MCRAE

    1
    Tellurium helix (Qin et al., Nature Electronics, 2020)

    To cram ever more computing power into your pocket, engineers need to come up with increasingly ingenious ways to add transistors to an already crowded space.

    Unfortunately there’s a limit to how small you can make a wire. But a twisted form of rare earth metal just might have what it takes to push the boundaries a little further.

    A team of researchers funded by the US Army have discovered a way to turn twisted nanowires of one of the rarest of rare earth metals, tellurium, into a material with just the right properties that make it an ideal transistor at just a couple of nanometres across.

    “This tellurium material is really unique,” says Peide Ye, an electrical engineer from Purdue University.

    “It builds a functional transistor with the potential to be the smallest in the world.”

    Transistors are the work horse of anything that computes information, using tiny changes in charge to prevent or allow larger currents to flow.

    Typically made of semiconducting materials, they can be thought of as traffic intersections for electrons. A small voltage change in one place opens the gate for current to flow, serving as both a switch and an amplifier.

    Combinations of open and closed switches are the physical units representing the binary language underpinning logic in computer operations. As such, the more you have in one spot, the more operations you can run.

    Ever since the first chunky transistor was prototyped a little more than 70 years ago, a variety of methods and novel materials have led to regular downsizing of the transistor.

    In fact the shrinking was so regular that co-founder of the computer giant Intel, George Moore, famously noted in 1965 that it would follow a trend of transistors doubling in density every two years.

    Today, that trend has slowed considerably. For one thing, more transistors in one spot means more heat building up.

    But there are also only so many ways you can shave atoms from a material and still have it function as a transistor. Which is where tellurium comes in.

    Though not exactly a common element in Earth’s crust, it’s a semi-metal in high demand, finding a place in a variety of alloys to improve hardness and help it resist corrosion.

    It also has properties of a semiconductor; carrying a current under some circumstances and acting as a resistor under others.

    Curious about its characteristics on a nanoscale, engineers grew single-dimensional chains of the element and took a close look at them under an electron microscope. Surprisingly, the super-thin ‘wire’ wasn’t exactly a neat line of atoms.

    “Silicon atoms look straight, but these tellurium atoms are like a snake. This is a very original kind of structure,” says Ye.

    On closer inspection they worked out that the chain was made of pairs of tellurium atoms bonded strongly together, and then stacking into a crystal form pulled into a helix by weaker van der Waal forces.

    Building any kind of electronics from a crinkly nanowire is just asking for trouble, so to give the material some structure the researchers went on the hunt for something to encapsulate it in.

    The solution, they found, was a nanotube of boron nitride. Not only did the tellurium helix slip neatly inside, the tube acted as an insulator, ticking all the boxes that would make it suit life as a transistor.

    Most importantly, the whole semiconducting wire was a mere 2 nanometres across, putting it in the same league as the 1 nanometre record set a few years ago.

    Time will tell if the team can squeeze it down further with fewer chains, or even if it will function as expected in a circuit.

    If it works as hoped, it could contribute to the next generation of miniaturised electronics, potentially halving the size of current cutting edge microchips.

    “Next, the researchers will optimise the device to further improve its performance, and demonstrate a highly efficient functional electronic circuit using these tiny transistors, potentially through collaboration with ARL researchers,” says Joe Qiu, program manager for the Army Research Office.

    Even if the concept pans out, there’s a variety of other challenges for shrinking technology to overcome before we’ll find it in our pockets.

    While tellurium isn’t currently considered to be a scarce resource, in spite of its relative rarity, it could be in high demand in future electronics such as solar cells.

    This research was published in Nature Electronics.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Purdue University is a public research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science, technology, and agriculture in his name. The first classes were held on September 16, 1874, with six instructors and 39 students.

    The main campus in West Lafayette offers more than 200 majors for undergraduates, over 69 masters and doctoral programs, and professional degrees in pharmacy and veterinary medicine. In addition, Purdue has 18 intercollegiate sports teams and more than 900 student organizations. Purdue is a member of the Big Ten Conference and enrolls the second largest student body of any university in Indiana, as well as the fourth largest foreign student population of any university in the United States.

     
  • richardmitnick 1:29 pm on February 22, 2020 Permalink | Reply
    Tags: "Time-resolved measurement in a memory device", , Data can be stored in magnetic tunnel junctions virtually without any error and in less than a nanosecond., , , Nanotechnology, , The researchers replaced the isolated metal dot by a magnetic tunnel junction., Tomorrow’s memory devices   

    From ETH Zürich: “Time-resolved measurement in a memory device” 

    ETH Zurich bloc

    From ETH Zürich

    19.02.2020
    Oliver Morsch

    Researchers at ETH have measured the timing of single writing events in a novel magnetic memory device with a resolution of less than 100 picoseconds. Their results are relevant for the next generation of main memories based on magnetism.

    1
    The chip produced by IMEC for the experiments at ETH. The tunnel junctions used to measure the timing of the magnetisation reversal are located at the centre (Image courtesy of IMEC).

    At the Department for Materials of the ETH in Zürich, Pietro Gambardella and his collaborators investigate tomorrow’s memory devices. They should be fast, retain data reliably for a long time and also be cheap. So-​called magnetic “random access memories” (MRAM) achieve this quadrature of the circle by combining fast switching via electric currents with durable data storage in magnetic materials. A few years ago researchers could already show that a certain physical effect – the spin-​orbit torque – makes particularly fast data storage possible. Now Gambardella’s group, together with the R&D-​centre IMEC in Belgium, managed to temporally resolve the exact dynamics of a single such storage event – and to use a few tricks to make it even faster.

    Magnetising with single spins

    To store data magnetically, one has to invert the direction of magnetisation of a ferromagnetic (that is, permanently magnetic) material in order to represent the information as a logic value, 0 or 1. In older technologies, such as magnetic tapes or hard drives, this is achieved through magnetic fields produced inside current-​carrying coils. Modern MRAM-​memories, by contrast, directly use the spins of electrons, which are magnetic, much like small compass needles, and flow directly through a magnetic layer as an electric current. In Gambardella’s experiments, electrons with opposite spin directions are spatially separated by the spin-​orbit interaction. This, in turn, creates an effective magnetic field, which can be used to invert the direction of magnetisation of a tiny metal dot.

    “We know from earlier experiments, in which we stroboscopically scanned a single magnetic metal dot with X-​rays, that the magnetisation reversal happens very fast, in about a nanosecond”, says Eva Grimaldi, a post-​doc in Gambardella’s group. “However, those were mean values averaged over many reversal events. Now we wanted to know how exactly a single such event takes place and to show that it can work on an industry-​compatible magnetic memory device.”

    Time resolution through a tunnel junction

    2
    Electron microscope image of the magnetic tunnel junction (MTJ, at the centre) and of the electrodes for controlling and measuring the reversal process. (Image: P. Gambardella / ETH Zürich)

    To do so, the researchers replaced the isolated metal dot by a magnetic tunnel junction. Such a tunnel junction contains two magnetic layers separated by an insulation layer that is only one nanometre thick. Depending on the spin direction – along the magnetisation of the magnetic layers, or opposite to it – the electrons can tunnel through that insulating layer more or less easily. This results in an electrical resistance that depends on the alignment of the magnetization in one layer with respect to the other and thus represents “0” and “1”. From the time dependence of that resistance during a reversal event, the researchers could reconstruct the exact dynamics of the process. In particular, they found that the magnetisation reversal happens in two stages: an incubation stage, during which the magnetisation stays constant, and the actual reversal stage, which lasts less than a nanosecond.

    3
    The magnetic tunnel junction (yellow and red disks) in which the magnetisation of the red disk is inverted by electron spins (blue and yellow arrows). The reversal process is measured through the tunnel resistance (vertical blue arrows).

    Small fluctuations

    “For a fast and reliable memory device it is essential that the time fluctuations between the individual reversal events are minimized”, explains Gambardella’s PhD student Viola Krizakova. So, based on their data the scientists developed a strategy to make those fluctuations as small as possible. To that end, they changed the current pulses used to control the magnetisation reversal in such a way as to introduce two additional physical phenomena. The so-​called spin-​transfer torque as well as a short voltage pulse during the reversal stage now resulted in a reduction of the total time for the reversal event to less than 0,3 nanoseconds, with temporal fluctuations of less than 0,2 nanoseconds.

    Application-​ready technology

    “Putting all of this together, we have found a method whereby data can be stored in magnetic tunnel junctions virtually without any error and in less than a nanosecond”, says Gambardella. Moreover, the collaboration with the research centre IMEC made it possible to test the new technology directly on an industry-​compatible wafer. Kevin Garello, a former post-​doc from Gambardella’s lab, produced the chips containing the tunnel contacts for the experiments at ETH and optimized the materials for them. In principle, the technology would, therefore, be immediately ready for use in a new generation of MRAM.

    Gambardella stresses that MRAM memories are particularly interesting because, differently from conventional main memories such as SRAM or DRAM, they don’t lose their information when the computer is switched off, but are still equally fast. He concedes, though, that the market for MRAM memories currently does not demand such high writing speeds since other technical bottlenecks such as power losses caused by large switching currents limit the access times. In the meantime, he and his co-​workers are already planning further improvements: they want to shrink the tunnel junctions and use different materials that use current more efficiently.

    Science paper:
    “Grimaldi E, et al. Single-​shot dynamics of spin–orbit torque and spin transfer torque switching in three-​terminal magnetic tunnel junctions.”
    Nature Nanotechnology

    See the full article here .

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    Please help promote STEM in your local schools.

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    ETH Zurich campus
    ETH Zürich is one of the leading international universities for technology and the natural sciences. It is well known for its excellent education, ground-breaking fundamental research and for implementing its results directly into practice.

    Founded in 1855, ETH Zürich today has more than 18,500 students from over 110 countries, including 4,000 doctoral students. To researchers, it offers an inspiring working environment, to students, a comprehensive education.

    Twenty-one Nobel Laureates have studied, taught or conducted research at ETH Zürich, underlining the excellent reputation of the university.

     
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