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  • richardmitnick 9:37 am on September 16, 2019 Permalink | Reply
    Tags: , Astronomical research, Nanoantenna-enabled detector, Nanotechnology,   

    From Sandia Lab- “Seeing infrared: Sandia’s nanoantennas help detectors see more heat, less noise” 

    From Sandia Lab

    September 16, 2019

    Kristen Meub
    klmeub@sandia.gov
    505-845-7215

    Sandia National Laboratories researchers have developed tiny, gold antennas to help cameras and sensors that “see” heat deliver clearer pictures of thermal infrared radiation for everything from stars and galaxies to people, buildings and items requiring security.

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    Sandia National Laboratories optical engineer Michael Goldflam sets up equipment to load and characterize a new nanoantenna-enabled detector. (Photo by Randy Montoya)

    In a Laboratory Directed Research and Development project, a team of researchers developed a nanoantenna-enabled detector that can boost the signal of a thermal infrared camera by up to three times and improve image quality by reducing dark current, a major component of image noise, by 10 to 100 times.

    Thermal infrared cameras and sensors have existed for 50 years, but the traditional design of the detector that sits behind the camera lens or a sensor’s optical system seems to be reaching its performance limits, said David Peters, a Sandia manager and nanoantenna project lead.

    He said improved sensitivity in infrared detectors, beyond what the typical design can deliver, is important for both Sandia’s national security work and for other uses, such as astronomical research.

    Seeing more with less

    The sensitivity and image quality of an infrared detector usually depends on a thick layer of detector material that absorbs incoming heat and turns it into an electrical signal that can be collected and turned into an image. The thickness of the detector layer determines how much heat can be absorbed and read by the camera, but thick layers also have drawbacks.

    “The detector material is always spontaneously creating electrons that are collected and add noise to the image, which reduces image quality,” Peters said. “This phenomenon, called dark current, increases along with the thickness of the detector material — the thicker the material is, the more noise in the image it creates.”

    The research team developed a new detector design that breaks away from relying on thick layers and instead uses a subwavelength nanoantenna, a patterned array of gold square or cross shapes, to concentrate the light on a thinner layer of detector material. This design uses just a fraction of a micron of detector material, whereas traditional thermal infrared detectors have a thickness of 5 to 10 microns. A human hair is about 75 microns in width.

    The nanoantenna-enhanced design helps detectors see more than 50% of an object’s infrared radiation while also reducing image distortion caused by dark current, whereas current technology can only see about 25% of infrared radiation. It also allows for the invention of new detector concepts that are not possible with existing technology.

    “For example, with nanoantennas, it’s possible to dramatically expand the amount of information acquired in an image by exquisitely controlling the spectral response at the pixel level,” Peters said.

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    Sandia National Laboratories’ nanoantenna-enabled detector on an assembled focal plane array for a thermal infrared camera. The gold nanoantennas are so small they aren’t visible on top of the detector array. (Photo courtesy of Sandia National Laboratories)

    The team makes the nanoantenna-enabled detectors by slightly altering the usual process for making an infrared detector. It starts by “growing” the detector material on top of a thin disk called a wafer. Then the detector material is flipped onto a layer of electronics that read the signals collected by the nanoantenna and the detector layer. After discarding the wafer, a tiny amount of gold is applied to create the patterned nanoantenna layer on top of the detector material.

    From national lab to industry

    “It was not a given that this was going to work, so that’s why Sandia took it on,” Peters said. “Now, we are to the point where we have proven this concept and this technology is ready to be commercialized. This concept can be applied to different detector types, so there’s an opportunity for existing manufacturers to integrate this new technology with their existing detectors.”

    Peters said Sandia is pursuing leads to establish a Collaborative Research and Development Agreement to start transferring the technology to industry.

    “This project is a perfect example of how a national lab can prove a concept and then spin it off to industry where it can be developed further,” Peters said.

    See the full article here .


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    Sandia Campus
    Sandia National Laboratory

    Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
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  • richardmitnick 8:46 am on September 16, 2019 Permalink | Reply
    Tags: , , Nanotechnology, , , Xeuss 2.0 X-ray scattering instrument   

    From Penn Today: “Researchers think small to make progress towards better fuel cells” 


    From Penn Today

    September 13, 2019
    Erica K. Brockmeier
    Eric Sucar Photographer

    A collaborative study describes how fuel cells, which use chemical energy to power cars and devices, can be developed using nanomaterials to be more cost-effective and efficient in the long term.

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    Graduate student Jennifer Lee uses a large transmission electron microscope, housed in the Singh Center, to take a closer look at the nanomaterials and nanocrystals that are synthesized in the lab.

    As renewable sources such as wind and solar are quickly changing the energy landscape, scientists are looking for ways to better store energy for when it’s needed. Fuel cells, which convert chemical energy into electrical power, are one possible solution for long-term energy storage, and could someday be used to power trucks and cars without burning fuel. But before fuel cells can be widely used, chemists and engineers need to find ways to make this technology more cost-effective and stable.

    A new study from the lab of Penn Integrates Knowledge Professor Christopher Murray, led by graduate student Jennifer Lee, shows how custom-designed nanomaterials can be used to address these challenges. In ACS Applied Materials & Interfaces, researchers show how a fuel cell can be built from cheaper, more widely available metals using an atomic-level design that also gives the material long-term stability. Former post-doc Davit Jishkariani and former students Yingrui Zhao and Stan Najmr, current student Daniel Rosen, and professors James Kikkawa and Eric Stach, also contributed to this work.

    The chemical reaction that powers a fuel cell relies on two electrodes, a negative anode and a positive cathode, separated by an electrolyte, a substance that allows the ions to move. When fuel enters the anode, a catalyst separates molecules into protons and electrons, with the latter traveling toward the cathode and creating an electric current.

    Catalysts are typically made of precious metals, like platinum, but because the chemical reactions only occur on the surface of the material, any atoms that are not presented on the surface of the material are wasted. It’s also important for catalysts to be stable for months and years because fuel cells are very difficult to replace.

    Chemists can address these two problems by designing custom nanomaterials that have platinum at the surface while using more common metals, such as cobalt, in the bulk to provide stability. The Murray group excels at creating well-controlled nanomaterials, known as nanocrystals, in which they can control the size, shape, and composition of any composite nanomaterial.

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    When not busy at the microscope or analyzing data, researchers in the Murray group work on synthesizing new nanomaterials.

    In this study, Lee focused on the catalyst in the cathode of a specific type of fuel cell known as a proton exchange membrane fuel cell. “The cathode is more of a problem, because the materials are either platinum or platinum-based, which are expensive and have slower reaction rates,” she says. “Designing the catalyst for the cathode is the main focus of designing a good fuel cell.”

    The challenge, explains Jishkariani, was in creating a cathode in which platinum and cobalt atoms would form into a stable structure. “We know cobalt and platinum mixes well; however, if you make alloys of these two, you have added atoms of platinum and cobalt in a random order,” he says. Adding more cobalt in a random order causes it to leach out into the electrode, meaning that the fuel cell will only function for a short time.

    To solve this problem, researchers designed a catalyst made of layered platinum and cobalt known as an intermetallic phase. By controlling exactly where each atom sat in the catalyst and locking the structure in place, the cathode catalyst was able to work for longer periods than when the atoms were arranged randomly. As an additional unexpected finding, the researchers found that adding more cobalt to the system led to greater efficiency, with a 1-to-1 ratio of platinum to cobalt, better than many other structures with a wide range of platinum-to-cobalt ratios.

    The next step will be to test and evaluate the intermetallic material in fuel cell assemblies to make direct comparisons to commercially-available systems. The Murray group will also be working on new ways to create the intermetallic structure without high temperatures and seeing if adding additional atoms improve the catalyst’s performance.

    3
    The Xeuss 2.0 X-ray scattering instrument, which came to the LRSM in 2018, helps researchers characterize the structures of a wide range of hard and soft materials.

    This work required high-resolution microscopic imaging, work that Lee previously did at Brookhaven National Lab but, thanks to recent acquisitions, can now be done at Penn in the Singh Center for Nanotechnology. “Many of the high-end experiments that we would have had to travel to around the country, sometimes around the world, we can now do much closer to home,” says Murray. “The advances that we’ve brought in electron microscopy and X-ray scattering are a fantastic addition for people that work on energy conversion and catalytic studies.”

    Lee also experienced first-hand how chemistry research directly connects to real world challenges. She recently presented this work at the International Precious Metals Institute conference and says that meeting members of the precious-metals community was enlightening. “There are companies looking at fuel cell technology and talking about the newest design of the fuel cell cars,” she says. “You get to interact with people that think of your project from different perspectives.”

    Murray sees this fundamental research as a starting point towards commercial implementation and real world application, emphasizing that future progress relies on the forward-looking research that’s happening now. “Thinking about a world where we’ve displaced a lot of the traditional fossil fuel-based inputs, if we can figure out this interconversion of electrical and chemical energy, that will address a couple of very important problems simultaneously.”

    This research was supported by the U.S. Department of Energy Fuel Cell Technology Office. This research used resources of the Center for Functional Nanomaterials of the Brookhaven National Laboratory, supported by the U.S. Department of Energy Office of Science Graduate Student Research (SCGSR) program.


    BNL Center for Functional Nanomaterials

    Magnetic property measurements were supported by the National Science Foundation Materials Research Science and Engineering Center Grant DMR-1720530.

    See the full article here .

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    U Penn campus

    Academic life at Penn is unparalleled, with 100 countries and every U.S. state represented in one of the Ivy League’s most diverse student bodies. Consistently ranked among the top 10 universities in the country, Penn enrolls 10,000 undergraduate students and welcomes an additional 10,000 students to our world-renowned graduate and professional schools.

    Penn’s award-winning educators and scholars encourage students to pursue inquiry and discovery, follow their passions, and address the world’s most challenging problems through an interdisciplinary approach.

     
  • richardmitnick 11:21 am on September 12, 2019 Permalink | Reply
    Tags: , Architected metamaterials, , , , , Nanotechnology   

    From Caltech: “New Metamaterial Morphs Into New Shapes, Taking on New Properties” 

    Caltech Logo

    From Caltech

    September 11, 2019

    Robert Perkins
    (626) 395‑1862
    rperkins@caltech.edu

    1

    A newly developed type of architected metamaterial has the ability to change shape in a tunable fashion.

    While most reconfigurable materials can toggle between two distinct states, the way a switch toggles on or off, the new material’s shape can be finely tuned, adjusting its physical properties as desired. The material, which has potential applications in next-generation energy storage and bio-implantable micro-devices, was developed by a joint Caltech-Georgia Tech-ETH Zürich team in the lab of Julia R. Greer.

    Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering in Caltech’s Division of Engineering and Applied Science, creates materials out of micro- and nanoscale building blocks that are arranged into sophisticated architectures that can be periodic, like a lattice, or non-periodic in a tailor-made fashion, giving them unusual physical properties.

    Most materials that are designed to change shape require a persistent external stimulus to change from one shape to another and stay that way: for example, they may be one shape when wet and a different shape when dry—like a sponge that swells as it absorbs water.

    By contrast, the new nanomaterial deforms through an electrochemically driven silicon-lithium alloying reaction, meaning that it can be finely controlled to attain any “in-between” states, remain in these configurations even upon the removal of the stimulus, and be easily reversed. Apply a little current, and a resulting chemical reaction changes the shape by a controlled, small degree. Apply a lot of current, and the shape changes substantially. Remove the electrical control, and the configuration is retained—just like tying off a balloon. A description of the new type of material was published online by the journal Nature on September 11.

    Defects and imperfections exist in all materials, and can often determine a material’s properties. In this case, the team chose to take advantage of that fact and build in defects to imbue the material with the properties they wanted.

    “The most intriguing part of this work to me is the critical role of defects in such dynamically responsive architected materials,” says Xiaoxing Xia, a graduate student at Caltech and lead author of the Nature paper.

    For the Nature paper, the team designed a silicon-coated lattice with microscale straight beams that bend into curves under electrochemical stimulation, taking on unique mechanical and vibrational properties. Greer’s team created these materials using an ultra-high-resolution 3D printing process called two-photon lithography. Using this novel fabrication method, they were able to build in defects in the architected material system, based on a pre-arranged design. In a test of the system, the team fabricated a sheet of the material that, under electrical control, reveals a Caltech icon.

    3

    “This just further shows that materials are just like people, it’s the imperfections that make them interesting. I have always had a particular liking for defects, and this time Xiaoxing managed to first uncover the effect of different types of defects on these metamaterials and then use them to program a particular pattern that would emerge in response to electrochemical stimulus,” says Greer.

    A material with such a finely controllable ability to change shape has potential in future energy storage systems because it provides a pathway to create adaptive energy storage systems that would enable batteries, for example, to be significantly lighter, safer, and to have substantially longer lives, Greer says. Some battery materials expand when storing energy, creating a mechanical degradation due to stress from the repeated expanding and contracting. Architected materials like this one can be designed to handle such structural transformations.

    “Electrochemically active metamaterials provide a novel pathway for development of next generation smart batteries with both increased capacity and novel functionalities. At Georgia Tech, we are developing the computational tools to predict this complex coupled electro-chemo-mechanical behavior,” says Claudio V. Di Leo, assistant professor of aerospace engineering at the Georgia Institute of Technology.

    See the full article here .


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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.”

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  • richardmitnick 12:41 pm on September 6, 2019 Permalink | Reply
    Tags: , Cryogenic transmission electron microscopy, Epitaxial growth, Gold loves to grow into little triangles., Gold triangles may be useful as photonic and plasmonic structures., , , Nanotechnology, Recording movies using electron microscopy., Self-assembled structures, , Ultimately we’d like to develop techniques for growing well-defined structures out of metal oxides especially if we can control the composition at each location on the structure., What happens when these 2-D materials and ordinary 3-D materials come together.   

    From MIT News: “Creating new opportunities from nanoscale materials” 

    MIT News

    From MIT News

    September 5, 2019
    Denis Paiste | Materials Research Laboratory

    1
    Left to right: Postdoc Shu Fen Tan, graduate student Kate Reidy, and Professor Frances Ross, all of the Department of Materials Science and Engineering, sit in front of a high vacuum evaporator system. The equipment was housed temporarily in MIT.nano while Ross’s lab was built out in Building 13. Photo: Denis Paiste/Materials Research Laboratory.

    2
    MIT Professor Frances Ross has designed several custom sample holders for examining nanoscale materials in gases and liquid media in the electron microscope. For liquid environments, thin windows of silicon nitride surround the liquid but allow the electron beam to pass through. For gas environments, the sample holder (shown here) must heat and tilt the sample without compromising its cleanliness. Photo: Denis Paiste/Materials Research Laboratory.

    3
    When gold is deposited on “dirty” graphene (left), blobs of gold collect around impurities. But when gold grows on graphene that has been heated and cleansed of impurities (right), it forms perfect triangles of gold. Images: Kate Reidy/MIT.

    5
    Professor Frances Ross (left), graduate student Kate Reidy (center), and postdoc Shu Fen Tan work together at the high vacuum evaporator chamber that is part of an electron microscopy suite donated to MIT by IBM. Photo: Denis Paiste/Materials Research Laboratory.

    6
    Niobium deposited on top of graphene produces structures that look like the frost patterns formed on the inside of windows in winter, or the feathery patterns of some ferns. They are called dendritic structures. Image: Kate Reidy/MIT.

    7
    An electron diffraction image of niobium deposited on top of graphene shows that certain crystal planes of niobium align with the crystal planes of the graphene, which is known as epitaxial growth. When a 3-D material is grown on top of a 2-D layer, this perfectly aligned atomic arrangement is often important for device makers. Image: Kate Reidy/MIT.

    8
    Clean deposition of gold nanoislands on molybdenum disulfide MoS2 with visible moiré patterns. Image: Kate Reidy/MIT.

    A hundred years ago, “2d” meant a two-penny, or 1-inch, nail. Today, “2-D” encompasses a broad range of atomically thin flat materials, many with exotic properties not found in the bulk equivalents of the same materials, with graphene — the single-atom-thick form of carbon — perhaps the most prominent. While many researchers at MIT and elsewhere are exploring two-dimensional materials and their special properties, Frances M. Ross, the Ellen Swallow Richards Professor in Materials Science and Engineering, is interested in what happens when these 2-D materials and ordinary 3-D materials come together.

    “We’re interested in the interface between a 2-D material and a 3-D material because every 2-D material that you want to use in an application, such as an electronic device, still has to talk to the outside world, which is three-dimensional,” Ross says.

    “We’re at an interesting time because there are immense developments in instrumentation for electron microscopy, and there is great interest in materials with very precisely controlled structures and properties, and these two things cross in a fascinating way,” says Ross.

    “The opportunities are very exciting,” Ross says. “We’re going to be really improving the characterization capabilities here at MIT.” Ross specializes in examining how nanoscale materials grow and react in both gases and liquid media, by recording movies using electron microscopy. Microscopy of reactions in liquids is particularly useful for understanding the mechanisms of electrochemical reactions that govern the performance of catalysts, batteries, fuel cells, and other important technologies. “In the case of liquid phase microscopy, you can also look at corrosion where things dissolve away, while in gases you can look at how individual crystals grow or how materials react with, say, oxygen,” she says.

    Ross joined the Department of Materials Science and Engineering (DMSE) faculty last year, moving from the nanoscale materials analysis department at the IBM Thomas J. Watson Research Center. “I learned a tremendous amount from my IBM colleagues and hope to extend our research in material design and growth in new directions,” she says.

    Recording movies

    During a recent visit to her lab, Ross explained an experimental setup donated to MIT by IBM. An ultra-high vacuum evaporator system arrived first, to be attached later directly onto a specially designed transmission electron microscope. “This gives powerful possibilities,” Ross explains. “We can put a sample in the vacuum, clean it, do all sorts of things to it such as heating and adding other materials, then transfer it under vacuum into the microscope, where we can do more experiments while we record images. So we can, for example, deposit silicon or germanium, or evaporate metals, while the sample is in the microscope and the electron beam is shining through it, and we are recording a movie of the process.”

    While waiting this spring for the transmission electron microscope to be set up, members of Ross’ seven-member research group, including materials science and engineering postdoc Shu Fen Tan and graduate student Kate Reidy, made and studied a variety of self-assembled structures. The evaporator system was housed temporarily on the fifth-level prototyping space of MIT.nano while Ross’s lab was being readied in Building 13. “MIT.nano had the resources and space; we were happy to be able to help,” says Anna Osherov, MIT.nano assistant director of user services.

    “All of us are interested in this grand challenge of materials science, which is: ‘How do you make a material with the properties you want and, in particular, how do you use nanoscale dimensions to tweak the properties, and create new properties, that you can’t get from bulk materials?’” Ross says.

    Using the ultra-high vacuum system, graduate student Kate Reidy formed structures of gold and niobium on several 2-D materials. “Gold loves to grow into little triangles,” Ross notes. “We’ve been talking to people in physics and materials science about which combinations of materials are the most important to them in terms of controlling the structures and the interfaces between the components in order to give some improvement in the properties of the material,” she notes.

    Shu Fen Tan synthesized nickel-platinum nanoparticles and examined them using another technique, liquid cell electron microscopy. She could arrange for only the nickel to dissolve, leaving behind spiky skeletons of platinum. “Inside the liquid cell, we are able to see this whole process at high spatial and temporal resolutions,” Tan says. She explains that platinum is a noble metal and less reactive than nickel, so under the right conditions the nickel participates in an electrochemical dissolution reaction and the platinum is left behind.

    Platinum is a well-known catalyst in organic chemistry and fuel cell materials, Tan notes, but it is also expensive, so finding combinations with less-expensive materials such as nickel is desirable.

    “This is an example of the range of materials reactions you can image in the electron microscope using the liquid cell technique,” Ross says. “You can grow materials; you can etch them away; you can look at, for example, bubble formation and fluid motion.”

    A particularly important application of this technique is to study cycling of battery materials. “Obviously, I can’t put an AA battery in here, but you could set up the important materials inside this very small liquid cell and then you can cycle it back and forth and ask, if I charge and discharge it 10 times, what happens? It does not work just as well as before — how does it fail?” Ross asks. “Some kind of failure analysis and all the intermediate stages of charging and discharging can be observed in the liquid cell.”

    “Microscopy experiments where you see every step of a reaction give you a much better chance of understanding what’s going on,” Ross says.

    Moiré patterns

    Graduate student Reidy is interested in how to control the growth of gold on 2-D materials such as graphene, tungsten diselenide, and molybdenum disulfide. When she deposited gold on “dirty” graphene, blobs of gold collected around the impurities. But when Reidy grew gold on graphene that had been heated and cleaned of impurities, she found perfect triangles of gold. Depositing gold on both the top and bottom sides of clean graphene, Reidy saw in the microscope features known as moiré patterns, which are caused when the overlapping crystal structures are out of alignment.

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    Physicists at MIT and Harvard University have found that graphene, a lacy, honeycomb-like sheet of carbon atoms, can behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance. Courtesy of the researchers.

    The gold triangles may be useful as photonic and plasmonic structures. “We think this could be important for a lot of applications, and it is always interesting for us to see what happens,” Reidy says. She is planning to extend her clean growth method to form 3-D metal crystals on stacked 2-D materials with various rotation angles and other mixed-layer structures. Reidy is interested in the properties of graphene and hexagonal boron nitride (hBN), as well as two materials that are semiconducting in their 2-D single-layer form, molybdenum disulfide (MoS2) and tungsten diselenide (WSe2). “One aspect that’s very interesting in the 2-D materials community is the contacts between 2-D materials and 3-D metals,” Reidy says. “If they want to make a semiconducting device or a device with graphene, the contact could be ohmic for the graphene case or a Schottky contact for the semiconducting case, and the interface between these materials is really, really important.”

    “You can also imagine devices using the graphene just as a spacer layer between two other materials,” Ross adds.

    For device makers, Reidy says it is sometimes important to have a 3-D material grow with its atomic arrangement aligned perfectly with the atomic arrangement in the 2-D layer beneath. This is called epitaxial growth. Describing an image of gold grown together with silver on graphene, Reidy explains, “We found that silver doesn’t grow epitaxially, it doesn’t make those perfect single crystals on graphene that we wanted to make, but by first depositing the gold and then depositing silver around it, we can almost force silver to go into an epitaxial shape because it wants to conform to what its gold neighbors are doing.”

    Electron microscope images can also show imperfections in a crystal such as rippling or bending, Reidy notes. “One of the great things about electron microscopy is that it is very sensitive to changes in the arrangement of the atoms,” Ross says. “You could have a perfect crystal and it would all look the same shade of gray, but if you have a local change in the structure, even a subtle change, electron microscopy can pick it up. Even if the change is just within the top few layers of atoms without affecting the rest of the material beneath, the image will show distinctive features that allow us to work out what’s going on.”

    Reidy also is exploring the possibilities of combining niobium — a metal that is superconducting at low temperatures — with a 2-D topological insulator, bismuth telluride. Topological insulators have fascinating properties whose discovery resulted in the Nobel Prize in Physics in 2016. “If you deposit niobium on top of bismuth telluride, with a very good interface, you can make superconducting junctions. We’ve been looking into niobium deposition, and rather than triangles we see structures that are more dendritic looking,” Reidy says. Dendritic structures look like the frost patterns formed on the inside of windows in winter, or the feathery patterns of some ferns. Changing the temperature and other conditions during the deposition of niobium can change the patterns that the material takes.

    All the researchers are eager for new electron microscopes to arrive at MIT.nano to give further insights into the behavior of these materials. “Many things will happen within the next year, things are ramping up already, and I have great people to work with. One new microscope is being installed now in MIT.nano and another will arrive next year. The whole community will see the benefits of improved microscopy characterization capabilities here,” Ross says.

    MIT.nano’s Osherov notes that two cryogenic transmission electron microscopes (cryo-TEM) are installed and running. “Our goal is to establish a unique microscopy-centered community. We encourage and hope to facilitate a cross-pollination between the cryo-EM researchers, primarily focused on biological applications and ‘soft’ material, as well as other research communities across campus,” she says. The latest addition of a scanning transmission electron microscope with enhanced analytical capabilities (ultrahigh energy resolution monochromator, 4-D STEM detector, Super-X EDS detector, tomography, and several in situ holders) brought in by John Chipman Associate Professor of Materials Science and Engineering James M. LeBeau, once installed, will substantially enhance the microscopy capabilities of the MIT campus. “We consider Professor Ross to be an immense resource for advising us in how to shape the in situ approach to measurements using the advanced instrumentation that will be shared and available to all the researchers within the MIT community and beyond,” Osherov says.

    Little drinking straws

    “Sometimes you know more or less what you are going to see during a growth experiment, but very often there’s something that you don’t expect,” Ross says. She shows an example of zinc oxide nanowires that were grown using a germanium catalyst. Some of the long crystals have a hole through their centers, creating structures which are like little drinking straws, circular outside but with a hexagonally shaped interior. “This is a single crystal of zinc oxide, and the interesting question for us is why do the experimental conditions create these facets inside, while the outside is smooth?” Ross asks. “Metal oxide nanostructures have so many different applications, and each new structure can show different properties. In particular, by going to the nanoscale you get access to a diverse set of properties.”

    “Ultimately, we’d like to develop techniques for growing well-defined structures out of metal oxides, especially if we can control the composition at each location on the structure,” Ross says. A key to this approach is self-assembly, where the material builds itself into the structure you want without having to individually tweak each component. “Self-assembly works very well for certain materials but the problem is that there’s always some uncertainty, some randomness or fluctuations. There’s poor control over the exact structures that you get. So the idea is to try to understand self-assembly well enough to be able to control it and get the properties that you want,” Ross says.

    “We have to understand how the atoms end up where they are, then use that self-assembly ability of atoms to make a structure we want. The way to understand how things self-assemble is to watch them do it, and that requires movies with high spatial resolution and good time resolution,” Ross explains. Electron microscopy can be used to acquire structural and compositional information and can even measure strain fields or electric and magnetic fields. “Imagine recording all of these things, but in a movie where you are also controlling how materials grow within the microscope. Once you have made a movie of something happening, you analyze all the steps of the growth process and use that to understand which physical principles were the key ones that determined how the structure nucleated and evolved and ended up the way it does.”

    Future directions

    Ross hopes to bring in a unique high-resolution, high vacuum TEM with capabilities to image materials growth and other dynamic processes. She intends to develop new capabilities for both water-based and gas-based environments. This custom microscope is still in the planning stages but will be situated in one of the rooms in the Imaging Suite in MIT.nano.

    “Professor Ross is a pioneer in this field,” Osherov says. “The majority of TEM studies to-date have been static, rather than dynamic. With static measurements you are observing a sample at one particular snapshot in time, so you don’t gain any information about how it was formed. Using dynamic measurements, you can look at the atoms hopping from state to state until they find the final position. The ability to observe self-assembling processes and growth in real time provides valuable mechanistic insights. We’re looking forward to bringing these advanced capabilities to MIT.nano.” she says.

    “Once a certain technique is disseminated to the public, it brings attention,” Osherov says. “When results are published, researchers expand their vision of experimental design based on available state-of-the-art capabilities, leading to many new experiments that will be focused on dynamic applications.”

    Rooms in MIT.nano feature the quietest space on the MIT campus, designed to reduce vibrations and electromagnetic interference to as low a level as possible. “There is space available for Professor Ross to continue her research and to develop it further,” Osherov says. “The ability of in situ monitoring the formation of matter and interfaces will find applications in multiple fields across campus, and lead to a further push of the conventional electron microscopy limits.”

    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 11:52 am on September 5, 2019 Permalink | Reply
    Tags: "Rice reactor turns greenhouse gas into pure liquid fuel", A common greenhouse gas could be repurposed in an efficient and environmentally friendly way with an electrolyzer that uses renewable electricity to produce pure liquid fuels., , “X-ray absorption spectroscopyenables us to probe the electronic structure of electrocatalysts in operando — that is during the actual chemical process.", , , Formic acid is an energy carrier. It’s a fuel-cell fuel that can generate electricity and emit carbon dioxide — which you can grab and recycle again., Formic acid produced by traditional carbon dioxide devices needs costly and energy-intensive purification steps Wang said., https://www.nature.com/articles/s41560-019-0451-x, In its latest prototype produces highly purified and high concentrations of formic acid., Nanotechnology, , The catalytic reactor developed by the Rice University lab of chemical and biomolecular engineer Haotian Wang uses carbon dioxide as its feedstock., The direct production of pure formic acid solutions will help to promote commercial carbon dioxide conversion technologies., The first was his development of a robust two-dimensional bismuth catalyst and the second a solid-state electrolyte that eliminates the need for salt as part of the reaction., The method is detailed in Nature Energy, The Rice lab worked with Brookhaven National Laboratory to view the process in progress., Two advances made the new device possible said lead author and Rice postdoctoral researcher Chuan Xia.   

    From Rice University: “Rice reactor turns greenhouse gas into pure liquid fuel” 

    Rice U bloc

    From Rice University

    September 3, 2019
    Mike Williams
    713-348-6728
    mikewilliams@rice.edu

    Lab’s ‘green’ invention reduces carbon dioxide into valuable fuels.

    1
    Rice postdoctoral researcher Chuan Xia, left, and chemical and biomolecular engineer Haotian Wang adjust their electrocatalysis reactor to produce liquid formic acid from carbon dioxide. Photo by Jeff Fitlow

    A common greenhouse gas could be repurposed in an efficient and environmentally friendly way with an electrolyzer that uses renewable electricity to produce pure liquid fuels.

    The catalytic reactor developed by the Rice University lab of chemical and biomolecular engineer Haotian Wang uses carbon dioxide as its feedstock and, in its latest prototype, produces highly purified and high concentrations of formic acid.

    Formic acid produced by traditional carbon dioxide devices needs costly and energy-intensive purification steps, Wang said. The direct production of pure formic acid solutions will help to promote commercial carbon dioxide conversion technologies.

    The method is detailed in Nature Energy.

    Wang, who joined Rice’s Brown School of Engineering in January, and his group pursue technologies that turn greenhouse gases into useful products. In tests, the new electrocatalyst reached an energy conversion efficiency of about 42%. That means nearly half of the electrical energy can be stored in formic acid as liquid fuel.

    “Formic acid is an energy carrier,” Wang said. “It’s a fuel-cell fuel that can generate electricity and emit carbon dioxide — which you can grab and recycle again.

    “It’s also fundamental in the chemical engineering industry as a feedstock for other chemicals, and a storage material for hydrogen that can hold nearly 1,000 times the energy of the same volume of hydrogen gas, which is difficult to compress,” he said. “That’s currently a big challenge for hydrogen fuel-cell cars.”

    2
    This schematic shows the electrolyzer developed at Rice to reduce carbon dioxide, a greenhouse gas, to valuable fuels. At left is a catalyst that selects for carbon dioxide and reduces it to a negatively charged formate, which is pulled through a gas diffusion layer (GDL) and the anion exchange membrane (AEM) into the central electrolyte. At the right, an oxygen evolution reaction (OER) catalyst generates positive protons from water and sends them through the cation exchange membrane (CEM). The ions recombine into formic acid or other products that are carried out of the system by deionized (DI) water and gas. Illustration by Chuan Xia and Demin Liu.

    Two advances made the new device possible, said lead author and Rice postdoctoral researcher Chuan Xia. The first was his development of a robust, two-dimensional bismuth catalyst and the second a solid-state electrolyte that eliminates the need for salt as part of the reaction.

    “Bismuth is a very heavy atom, compared to transition metals like copper, iron or cobalt,” Wang said. “Its mobility is much lower, particularly under reaction conditions. So that stabilizes the catalyst.” He noted the reactor is structured to keep water from contacting the catalyst, which also helps preserve it.

    Xia can make the nanomaterials in bulk. “Currently, people produce catalysts on the milligram or gram scales,” he said. “We developed a way to produce them at the kilogram scale. That will make our process easier to scale up for industry.”

    3
    Rice postdoctoral researcher Chuan Xia, left, and chemical and biomolecular engineer Haotian Wang. Photo by Jeff Fitlow

    The polymer-based solid electrolyte is coated with sulfonic acid ligands to conduct positive charge or amino functional groups to conduct negative ions. “Usually people reduce carbon dioxide in a traditional liquid electrolyte like salty water,” Wang said. “You want the electricity to be conducted, but pure water electrolyte is too resistant. You need to add salts like sodium chloride or potassium bicarbonate so that ions can move freely in water.

    “But when you generate formic acid that way, it mixes with the salts,” he said. “For a majority of applications you have to remove the salts from the end product, which takes a lot of energy and cost. So we employed solid electrolytes that conduct protons and can be made of insoluble polymers or inorganic compounds, eliminating the need for salts.”

    The rate at which water flows through the product chamber determines the concentration of the solution. Slow throughput with the current setup produces a solution that is nearly 30% formic acid by weight, while faster flows allow the concentration to be customized. The researchers expect to achieve higher concentrations from next-generation reactors that accept gas flow to bring out pure formic acid vapors.

    The Rice lab worked with Brookhaven National Laboratory to view the process in progress. “X-ray absorption spectroscopy, a powerful technique available at the Inner Shell Spectroscopy (ISS) beamline at Brookhaven Lab’s National Synchrotron Light Source II, enables us to probe the electronic structure of electrocatalysts in operando — that is, during the actual chemical process,” said co-author Eli Stavitski, lead beamline scientist at ISS. “In this work, we followed bismuth’s oxidation states at different potentials and were able to identify the catalyst’s active state during carbon dioxide reduction.”


    BNL NSLS II

    With its current reactor, the lab generated formic acid continuously for 100 hours with negligible degradation of the reactor’s components, including the nanoscale catalysts. Wang suggested the reactor could be easily retooled to produce such higher-value products as acetic acid, ethanol or propanol fuels.

    4
    An electrocatalysis reactor built at Rice recycles carbon dioxide to produce pure liquid fuel solutions using electricity. The scientists behind the invention hope it will become an efficient and profitable way to reuse the greenhouse gas and keep it out of the atmosphere. Photo by Jeff Fitlow

    “The big picture is that carbon dioxide reduction is very important for its effect on global warming as well as for green chemical synthesis,” Wang said. “If the electricity comes from renewable sources like the sun or wind, we can create a loop that turns carbon dioxide into something important without emitting more of it.”

    Co-authors are Rice graduate student Peng Zhu; graduate student Qiu Jiang and Husam Alshareef, a professor of material science and engineering, at King Abdullah University of Science and Technology, Saudi Arabia (KAUST); postdoctoral researcher Ying Pan of Harvard University; and staff scientist Wentao Liang of Northeastern University. Wang is the William Marsh Rice Trustee Assistant Professor of Chemical and Biomolecular Engineering. Xia is a J. Evans Attwell-Welch Postdoctoral Fellow at Rice.

    Rice and the U.S. Department of Energy Office of Science User Facilities supported the research.

    5
    Eli Stavitski, lead scientist at the Inner Shell Spectroscopy (ISS) beamline at Brookhaven National Laboratory’s National Synchrotron Light Source II, used the powerful tool to probe bismuth’s oxidation states, part of the process developed at Rice University to recycle carbon dioxide to produce pure liquid fuel solutions using electricity. (Credit: Brookhaven National Laboratory)

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings


    Stem Education Coalition

    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 8:10 am on August 30, 2019 Permalink | Reply
    Tags: Advanced nanolithography, ALD-Atomic layer deposition, , , , EUVL-Extreme ultraviolet lithography, , Nanotechnology, PMMA-Polymer poly(methyl methacrylate),   

    From Brookhaven National Lab: “Enhancing Materials for Hi-Res Patterning to Advance Microelectronics” 

    From Brookhaven National Lab

    August 27, 2019
    Ariana Manglaviti
    amanglaviti@bnl.gov
    (631) 344-2347

    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174

    Scientists at Brookhaven Lab’s Center for Functional Nanomaterials [below] created “hybrid” organic-inorganic materials for transferring ultrasmall, high-aspect-ratio features into silicon for next-generation electronic devices.

    1
    (Left to right): Ashwanth Subramanian, Ming Lu, Kim Kisslinger, Chang-Yong Nam, and Nikhil Tiwale in the Electron Microscopy Facility at Brookhaven Lab’s Center for Functional Nanomaterials. The scientists used scanning electron microscopes to image high-resolution, high-aspect-ratio silicon nanostructures they etched using a “hybrid” organic-inorganic resist.

    To increase the processing speed and reduce the power consumption of electronic devices, the microelectronics industry continues to push for smaller and smaller feature sizes. Transistors in today’s cell phones are typically 10 nanometers (nm) across—equivalent to about 50 silicon atoms wide—or smaller. Scaling transistors down below these dimensions with higher accuracy requires advanced materials for lithography—the primary technique for printing electrical circuit elements on silicon wafers to manufacture electronic chips. One challenge is developing robust “resists,” or materials that are used as templates for transferring circuit patterns into device-useful substrates such as silicon.

    Now, scientists from the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory—have used the recently developed technique of infiltration synthesis to create resists that combine the organic polymer poly(methyl methacrylate), or PMMA, with inorganic aluminum oxide. Owing to its low cost and high resolution, PMMA is the most widely used resist in electron-beam lithography (EBL), a kind of lithography in which electrons are used to create the pattern template. However, at the resist thicknesses that are necessary to generate the ultrasmall feature sizes, the patterns typically start to degrade when they are etched into silicon, failing to produce the required high aspect ratio (height to width).

    As reported in a paper published online on July 8 in the Journal of Materials Chemistry C, these “hybrid” organic-inorganic resists exhibit a high lithographic contrast and enable the patterning of high-resolution silicon nanostructures with a high aspect ratio. By changing the amount of aluminum oxide (or a different inorganic element) infiltrated into PMMA, the scientists can tune these parameters for particular applications. For example, next-generation memory devices such as flash drives will be based on a three-dimensional stacking structure to increase memory density, so an extremely high aspect ratio is desirable; on the other hand, a very high resolution is the most important characteristic for future processor chips.

    “Instead of taking an entirely new synthesis route, we used an existing resist, an inexpensive metal oxide, and common equipment found in almost every nanofabrication facility,” said first author Nikhil Tiwale, a postdoctoral research associate in the CFN Electronic Nanomaterials Group.

    Though other hybrid resists have been proposed, most of them require high electron doses (intensities), involve complex chemical synthesis methods, or have expensive proprietary compositions. Thus, these resists are not optimal for the high-rate, high-volume manufacture of next-generation electronics.

    Advanced nanolithography for high-volume manufacturing

    Conventionally, the microelectronics industry has relied upon optical lithography, whose resolution is limited by the wavelength of light that the resist gets exposed to. However, EBL and other nanolithography techniques such as extreme ultraviolet lithography (EUVL) can push this limit because of the very small wavelength of electrons and high-energy ultraviolet light. The main difference between the two techniques is the exposure process.

    “In EBL, you need to write all of the area you need to expose line by line, kind of like making a sketch with a pencil,” said Tiwale. “By contrast, in EUVL, you can expose the whole area in one shot, akin to taking a photograph. From this point of view, EBL is great for research purposes, and EUVL is better suited for high-volume manufacturing. We believe that the approach we demonstrated for EBL can be directly applied to EUVL, which companies including Samsung have recently started using to develop manufacturing processes for their 7 nm technology node.”

    In this study, the scientists used an atomic layer deposition (ALD) system—a standard piece of nanofabrication equipment for depositing ultrathin films on surfaces—to combine PMMA and aluminum oxide. After placing a substrate coated with a thin film of PMMA into the ALD reaction chamber, they introduced a vapor of an aluminum precursor that diffused through tiny molecular pores inside the PMMA matrix to bind with the chemical species inside the polymer chains. Then, they introduced another precursor (such as water) that reacted with the first precursor to form aluminum oxide inside the PMMA matrix. These steps together constitute one processing cycle.

    2
    A schematic showing the process of creating the hybrid organic-inorganic resist through infiltration synthesis, patterning the resist via electron-beam lithography, and etching the pattern into silicon by bombarding the silicon surface with ions of sulfur hexafluoride (SF6).

    The team then performed EBL with hybrid resists that had up to eight processing cycles. To characterize the contrast of the resists under different electron doses, the scientists measured the change in resist thickness within the exposed areas. Surface height maps generated with an atomic force microscope (a microscope with an atomically sharp tip for tracking the topography of a surface) and optical measurements obtained through ellipsometry (a technique for determining film thickness based on the change in the polarization of light reflected from a surface) revealed that the thickness changes gradually with a low number of processing cycles but rapidly with additional cycles—i.e., a higher aluminum oxide content.

    “The contrast refers to how fast the resist changes after being exposed to the electron beam,” explained Chang-Yong Nam, a materials scientist in the CFN Electronic Nanomaterials Group, who supervised the project and conceived the idea in collaboration with Jiyoung Kim, a professor in the Department of Materials Science and Engineering at the University of Texas at Dallas. “The abrupt change in the height of the exposed regions suggests an increase in the resist contrast for higher numbers of infiltration cycles—almost six times higher than that of the original PMMA resist.”

    The scientists also used the hybrid resists to pattern periodic straight lines and “elbows” (intersecting lines) in silicon substrates, and compared the etch rate of the resists with substrates.

    3
    Left: A scanning electron microscope (SEM) image of silicon elbow-shaped nanopatterns with different feature sizes (linewidths). Right: A high-magnification SEM image of high-resolution, high-aspect-ratio silicon nanostructures patterned at a pitch resolution (linewidth plus spacewidth, or space between lines) of 500 nm.

    “You want silicon to be etched faster than the resist; otherwise the resist starts to degrade,” said Nam. “We found that the etch selectivity of our hybrid resist is higher than that of costly proprietary resists (e.g., ZEP) and techniques that use an intermediate “hard” mask layer such as silicon dioxide to prevent pattern degradation, but which require additional processing steps.”

    3
    After two processing cycles, the etch selectivity of the hybrid resist surpasses that of ZEP, a costly resist. After four cycles, the hybrid resist has a 40 percent higher etch selectivity than that of silicon dioxide (SiO2).

    Going forward, the team will study how the hybrid resists respond to EUV exposure. They have already started using soft x-rays (energy range corresponding to the wavelength of EUV light) at Brookhaven’s National Synchrotron Light Source II (NSLS-II) [below], and hope to use a dedicated EUV beamline operated by the Center for X-ray Optics at Lawrence Berkeley National Lab’s Advanced Light Source (ALS) in collaboration with industry partners.

    LBNL ALS

    “The energy absorption by the organic layer of EUVL resists is very weak,” said Nam. “Adding inorganic elements, such as tin or zirconium, can make them more sensitive to EUV light. We look forward to exploring how our approach can address the resist performance requirements of EUVL.”

    Both NSLS-II and ALS are DOE User Facilities.

    The other co-authors are CFN scientists Kim Kisslinger, Ming Lu, and Aaron Stein; and Ashwanth Subramanian, a PhD student in the Department of Materials Science and Chemical Engineering at Stony Brook University and a graduate research assistant at the CFN.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus


    BNL Center for Functional Nanomaterials

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 7:09 am on August 30, 2019 Permalink | Reply
    Tags: , , , , Nanotechnology, Small-angle x-ray scattering,   

    From Brookhaven National Lab: “Smarter Experiments for Faster Materials Discovery” 

    From Brookhaven National Lab

    August 28, 2019
    Cara Laasch,
    laasch@bnl.gov
    (631) 344-8458,

    Peter Genzer,
    genzer@bnl.gov
    (631) 344-3174

    Scientists created a new AI algorithm for making measurement decisions; autonomous approach could revolutionize scientific experiments.

    1
    (From left to right) Kevin Yager, Masafumi Fukuto, and Ruipeng Li prepared the Complex Materials Scattering (CMS) beamline at NSLS-II for a measurement using the new decision-making algorithm, which was developed by Marcus Noack (not pictured).

    A team of scientists from the U.S. Department of Energy’s Brookhaven National Laboratory and Lawrence Berkeley National Laboratory designed, created, and successfully tested a new algorithm to make smarter scientific measurement decisions.

    The algorithm, a form of artificial intelligence (AI), can make autonomous decisions to define and perform the next step of an experiment. The team described the capabilities and flexibility of their new measurement tool in a paper published on August 14, 2019 in Nature Scientific Reports.

    From Galileo and Newton to the recent discovery of gravitational waves, performing scientific experiments to understand the world around us has been the driving force of our technological advancement for hundreds of years. Improving the way researchers do their experiments can have tremendous impact on how quickly those experiments yield applicable results for new technologies.

    Over the last decades, researchers have sped up their experiments through automation and an ever-growing assortment of fast measurement tools. However, some of the most interesting and important scientific challenges—such as creating improved battery materials for energy storage or new quantum materials for new types of computers—still require very demanding and time-consuming experiments.

    By creating a new decision-making algorithm as part of a fully automated experimental setup, the interdisciplinary team from two of Brookhaven’s DOE Office of Science user facilities—the Center for Functional Nanomaterials (CFN) [below] and the National Synchrotron Light Source II (NSLS-II) [below]—and Berkeley Lab’s Center for Advanced Mathematics for Energy Research Applications (CAMERA) offers the possibility to study these challenges in a more efficient fashion.

    2

    The challenge of complexity

    The goal of many experiments is to gain knowledge about the material that is studied, and scientists have a well-tested way to do this: They take a sample of the material and measure how it reacts to changes in its environment.

    A standard approach for scientists at user facilities like NSLS-II and CFN is to manually scan through the measurements from a given experiment to determine the next area where they might want to run an experiment. But access to these facilities’ high-end materials-characterization tools is limited, so measurement time is precious. A research team might only have a few days to measure their materials, so they need to make the most out of each measurement.

    “The key to achieving a minimum number of measurements and maximum quality of the resulting model is to go where uncertainties are large,” said Marcus Noack, a postdoctoral scholar at CAMERA and lead author of the study. “Performing measurements there will most effectively reduce the overall model uncertainty.”

    As Kevin Yager, a co-author and CFN scientist, pointed out, “The final goal is not only to take data faster but also to improve the quality of the data we collect. I think of it as experimentalists switching from micromanaging their experiment to managing at a higher level. Instead of having to decide where to measure next on the sample, the scientists can instead think about the big picture, which is ultimately what we as scientists are trying to do.”

    “This new approach is an applied example of artificial intelligence,” said co-author Masafumi Fukuto, a scientist at NSLS-II. “The decision-making algorithm is replacing the intuition of the human experimenter and can scan through the data and make smart decisions about how the experiment should proceed.”

    3
    This animation shows a comparison between a traditional grid measurement (left) of a sample with a measurement steered by the newly-developed decision-making algorithm (right). This comparison shows that the algorithm can identify the edges and inner part of the sample and focuses the measurement in these regions to gain more knowledge about the sample.

    More information for less?

    In practice, before starting an experiment, the scientists define a set of goals they want to get out of the measurement. With these goals set, the algorithm looks at the previously measured data while the experiment is ongoing to determine the next measurement. On its search for the best next measurement, the algorithm creates a surrogate model of the data, which is an educated guess as to how the material will behave in the next possible steps, and calculates the uncertainty—basically how confident it is in its guess—for each possible next step. Based on this, it then selects the most uncertain option to measure next. The trick here is by picking the most uncertain step to measure next, the algorithm maximizes the amount of knowledge it gains by making that measurement. The algorithm not only maximizes the information gain during the measurement, it also defines when to end the experiment by figuring out the moment when any additional measurements would not result in more knowledge.

    “The basic idea is, given a bunch of experiments, how can you automatically pick the next best one?” said James Sethian, director of CAMERA and a co-author of the study. “Marcus has built a world which builds an approximate surrogate model on the basis of your previous experiments and suggests the best or most appropriate experiment to try next.”

    4
    To use the decision-making algorithm for their measurements, the team needed to automate the measurement and also the data analysis. This image shows how all pieces are integrated with each other to form a closed looped. The algorithm receives analyzed data from the last measurement step, adds this data to its model, calculates the best next step, and sends its decision to the beamline to execute the next measurement.

    How we got here

    To make autonomous experiments a reality, the team had to tackle three important pieces: the automation of the data collection, real-time analysis, and, of course, the decision-making algorithm.

    “This is an exciting part of this collaboration,” said Fukuto. “We all provided an essential piece for it: The CAMERA team worked on the decision-making algorithm, Kevin from CFN developed the real-time data analysis, and we at NSLS-II provided the automation for the measurements.”

    The team first implemented their decision-making algorithm at the Complex Materials Scattering (CMS) beamline at NSLS-II, which the CFN and NSLS-II operate in partnership. This instrument offers ultrabright x-rays to study the nanostructure of various materials. As the lead beamline scientist of this instrument, Fukuto had already designed the beamline with automation in mind. The beamline offers a sample-exchanging robot, automatic sample movement in various directions, and many other helpful tools to ensure fast measurements. Together with Yager’s real-time data analysis, the beamline was—by design—the perfect fit for the first “smart” experiment.

    The first “smart” experiment

    The first fully autonomous experiment the team performed was to map the perimeter of a droplet where nanoparticles segregate using a technique called small-angle x-ray scattering at the CMS beamline. During small-angle x-ray scattering, the scientists shine bright x-rays at the sample and, depending on the atomic to nanoscale structure of the sample, the x-rays bounce off in different directions. The scientists then use a large detector to capture the scattered x-rays and calculate the properties of the sample at the illuminated spot. In this first experiment, the scientists compared the standard approach of measuring the sample with measurements taken when the new decision-making algorithm was calling the shots. The algorithm was able to identify the area of the droplet and focused on its edges and inner parts instead of the background.

    “After our own initial success, we wanted to apply the algorithm more, so we reached out to a few users and proposed to test our new algorithm on their scientific problems,” said Yager. “They said yes, and since then we have measured various samples. One of the most interesting ones was a study on a sample that was fabricated to contain a spectrum of different material types. So instead of making and measuring an enormous number of samples and maybe missing an interesting combination, the user made one single sample that included all possible combinations. Our algorithm was then able to explore this enormous diversity of combinations efficiently,” he said.

    What’s next?

    After the first successful experiments, the scientists plan to further improve the algorithm and therefore its value to the scientific community. One of their ideas is to make the algorithm “physics-aware”—taking advantage of anything already known about material under study—so the method can be even more effective. Another development in progress is to use the algorithm during synthesis and processing of new materials, for example to understand and optimize processes relevant to advanced manufacturing as these materials are incorporated into real-world devices. The team is also thinking about the larger picture and wants to transfer the autonomous method to other experimental setups.

    “I think users view the beamlines of NSLS-II or microscopes of CFN just as powerful characterization tools. We are trying to change these capabilities into a powerful material discovery facility,” Fukuto said.

    This work was funded by the DOE Office of Science (ASCR and BES).

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus


    BNL Center for Functional Nanomaterials

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
    i1

     
  • richardmitnick 3:48 pm on August 28, 2019 Permalink | Reply
    Tags: "MIT engineers build advanced microprocessor out of carbon nanotubes", , , , Nanotechnology   

    From MIT News: “MIT engineers build advanced microprocessor out of carbon nanotubes” 

    MIT News

    From MIT News

    August 28, 2019
    Rob Matheson

    1
    A close up of a modern microprocessor built from carbon nanotube field-effect transistors. Image: Felice Frankel

    2
    MIT engineers have built a modern microprocessor from carbon nanotube field-effect transistors (pictured), which are seen as faster and greener than silicon transistors. The new approach uses the same fabrication processes used for silicon chips. Image courtesy of the researchers

    New approach harnesses the same fabrication processes used for silicon chips, offers key advance toward next-generation computers.

    After years of tackling numerous design and manufacturing challenges, MIT researchers have built a modern microprocessor from carbon nanotube transistors, which are widely seen as a faster, greener alternative to their traditional silicon counterparts.

    The microprocessor, described today in the journal Nature, can be built using traditional silicon-chip fabrication processes, representing a major step toward making carbon nanotube microprocessors more practical.

    Silicon transistors — critical microprocessor components that switch between 1 and 0 bits to carry out computations — have carried the computer industry for decades. As predicted by Moore’s Law, industry has been able to shrink down and cram more transistors onto chips every couple of years to help carry out increasingly complex computations. But experts now foresee a time when silicon transistors will stop shrinking, and become increasingly inefficient.

    Making carbon nanotube field-effect transistors (CNFET) has become a major goal for building next-generation computers. Research indicates CNFETs have properties that promise around 10 times the energy efficiency and far greater speeds compared to silicon. But when fabricated at scale, the transistors often come with many defects that affect performance, so they remain impractical.

    The MIT researchers have invented new techniques to dramatically limit defects and enable full functional control in fabricating CNFETs, using processes in traditional silicon chip foundries. They demonstrated a 16-bit microprocessor with more than 14,000 CNFETs that performs the same tasks as commercial microprocessors. The paper describes the microprocessor design and includes more than 70 pages detailing the manufacturing methodology.

    The microprocessor is based on the RISC-V open-source chip architecture that has a set of instructions that a microprocessor can execute. The researchers’ microprocessor was able to execute the full set of instructions accurately. It also executed a modified version of the classic “Hello, World!” program, printing out, “Hello, World! I am RV16XNano, made from CNTs.”

    “This is by far the most advanced chip made from any emerging nanotechnology that is promising for high-performance and energy-efficient computing,” says co-author Max M. Shulaker, the Emanuel E Landsman Career Development Assistant Professor of Electrical Engineering and Computer Science (EECS) and a member of the Microsystems Technology Laboratories. “There are limits to silicon. If we want to continue to have gains in computing, carbon nanotubes represent one of the most promising ways to overcome those limits. [The paper] completely re-invents how we build chips with carbon nanotubes.”

    Joining Shulaker on the paper are: first author and postdoc Gage Hills, graduate students Christian Lau, Andrew Wright, Mindy D. Bishop, Tathagata Srimani, Pritpal Kanhaiya, Rebecca Ho, and Aya Amer, all of EECS; Arvind, the Johnson Professor of Computer Science and Engineering and a researcher in the Computer Science and Artificial Intelligence Laboratory; Anantha Chandrakasan, the dean of the School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science; and Samuel Fuller, Yosi Stein, and Denis Murphy, all of Analog Devices.

    Fighting the “bane” of CNFETs

    The microprocessor builds on a previous iteration designed by Shulaker and other researchers six years ago that had only 178 CNFETs and ran on a single bit of data. Since then, Shulaker and his MIT colleagues have tackled three specific challenges in producing the devices: material defects, manufacturing defects, and functional issues. Hills did the bulk of the microprocessor design, while Lau handled most of the manufacturing.

    For years, the defects intrinsic to carbon nanotubes have been a “bane of the field,” Shulaker says. Ideally, CNFETs need semiconducting properties to switch their conductivity on an off, corresponding to the bits 1 and 0. But unavoidably, a small portion of carbon nanotubes will be metallic, and will slow or stop the transistor from switching. To be robust to those failures, advanced circuits will need carbon nanotubes at around 99.999999 percent purity, which is virtually impossible to produce today.

    The researchers came up with a technique called DREAM (an acronym for “designing resiliency against metallic CNTs”), which positions metallic CNFETs in a way that they won’t disrupt computing. In doing so, they relaxed that stringent purity requirement by around four orders of magnitude — or 10,000 times — meaning they only need carbon nanotubes at about 99.99 percent purity, which is currently possible.

    Designing circuits basically requires a library of different logic gates attached to transistors that can be combined to, say, create adders and multipliers — like combining letters in the alphabet to create words. The researchers realized that the metallic carbon nanotubes impacted different pairings of these gates differently. A single metallic carbon nanotube in gate A, for instance, may break the connection between A and B. But several metallic carbon nanotubes in gates B may not impact any of its connections.

    In chip design, there are many ways to implement code onto a circuit. The researchers ran simulations to find all the different gate combinations that would be robust and wouldn’t be robust to any metallic carbon nanotubes. They then customized a chip-design program to automatically learn the combinations least likely to be affected by metallic carbon nanotubes. When designing a new chip, the program will only utilize the robust combinations and ignore the vulnerable combinations.

    “The ‘DREAM’ pun is very much intended, because it’s the dream solution,” Shulaker says. “This allows us to buy carbon nanotubes off the shelf, drop them onto a wafer, and just build our circuit like normal, without doing anything else special.”

    Exfoliating and tuning

    CNFET fabrication starts with depositing carbon nanotubes in a solution onto a wafer with predesigned transistor architectures. However, some carbon nanotubes inevitably stick randomly together to form big bundles — like strands of spaghetti formed into little balls — that form big particle contamination on the chip.

    To cleanse that contamination, the researchers created RINSE (for “removal of incubated nanotubes through selective exfoliation”). The wafer gets pretreated with an agent that promotes carbon nanotube adhesion. Then, the wafer is coated with a certain polymer and dipped in a special solvent. That washes away the polymer, which only carries away the big bundles, while the single carbon nanotubes remain stuck to the wafer. The technique leads to about a 250-times reduction in particle density on the chip compared to similar methods.

    Lastly, the researchers tackled common functional issues with CNFETs. Binary computing requires two types of transistors: “N” types, which turn on with a 1 bit and off with a 0 bit, and “P” types, which do the opposite. Traditionally, making the two types out of carbon nanotubes has been challenging, often yielding transistors that vary in performance. For this solution, the researchers developed a technique called MIXED (for “metal interface engineering crossed with electrostatic doping”), which precisely tunes transistors for function and optimization.

    In this technique, they attach certain metals to each transistor — platinum or titanium — which allows them to fix that transistor as P or N. Then, they coat the CNFETs in an oxide compound through atomic-layer deposition, which allows them to tune the transistors’ characteristics for specific applications. Servers, for instance, often require transistors that act very fast but use up energy and power. Wearables and medical implants, on the other hand, may use slower, low-power transistors.

    The main goal is to get the chips out into the real world. To that end, the researchers have now started implementing their manufacturing techniques into a silicon chip foundry through a program by Defense Advanced Research Projects Agency, which supported the research. Although no one can say when chips made entirely from carbon nanotubes will hit the shelves, Shulaker says it could be fewer than five years. “We think it’s no longer a question of if, but when,” he says.

    The work was also supported by Analog Devices, the National Science Foundation, and the Air Force Research Laboratory.

    See the full article here .


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  • richardmitnick 3:13 pm on August 18, 2019 Permalink | Reply
    Tags: "Micron Starts Volume Production of 1z Nanometer DRAM Process Node", Advancement in DRAM scaling, , , Micron Technology, Nanotechnology   

    From insideHPC: “Micron Starts Volume Production of 1z Nanometer DRAM Process Node” 

    From insideHPC

    August 18, 2019

    1

    Today Micron Technology announced advancements in DRAM scaling, making Micron the first memory company to begin mass production of 16Gb DDR4 products using 1z nm process technology.

    “Development and mass production of the industry’s smallest feature size DRAM node are a testament to Micron’s world-class engineering and manufacturing capabilities, especially at a time when DRAM scaling is becoming extremely complex,” said Scott DeBoer, executive vice president of Technology Development for Micron Technology. “Being first to market strongly positions us to continue offering high-value solutions across a wide portfolio of end customer applications.”

    Micron’s 1z nm 16Gb DDR4 product delivers substantially higher bit density, as well as significant performance enhancements and lower cost compared to the previous generation 1Y nm node. It also reinforces Micron’s continued progress in delivering improvements in relative performance and power consumption for compute DRAM (DDR4), mobile DRAM (LPDDR4) and graphics DRAM (GDDR6) product lines. The optimized balance between power and performance will be a key differentiator for applications including, among others, artificial intelligence, autonomous vehicles, 5G, mobile devices, graphics, gaming, network infrastructure and servers.

    “Micron initiated the transition to 1z nm with mass production of its 16Gb DDR4 memory solution. Production using the smaller node delivers several benefits, including an approximately 40% reduction in power consumption compared to previous generations of 8Gb DDR4-based products. Micron’s comprehensive portfolio of 1z nm DDR4 products targets the growing need for better performance, higher density and reduced power consumption in the modern data center.”

    Separately, Micron is also announcing today that it has begun volume shipments of the industry’s highest-capacity monolithic 16Gb low-power double data rate 4X (LPDDR4X) DRAM in UFS-based multichip packages (uMCP4). Micron’s 1z nm LPDDR4X and uMCP4 address the needs of mobile device manufacturers seeking low power and smaller packages to design devices with attractive form factors and long battery life.

    See the full article here .

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    Founded on December 28, 2006, insideHPC is a blog that distills news and events in the world of HPC and presents them in bite-sized nuggets of helpfulness as a resource for supercomputing professionals. As one reader said, we’re sifting through all the news so you don’t have to!

    If you would like to contact me with suggestions, comments, corrections, errors or new company announcements, please send me an email at rich@insidehpc.com. Or you can send me mail at:

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  • richardmitnick 8:22 am on August 15, 2019 Permalink | Reply
    Tags: , , , , Nanotechnology, ,   

    From University of Washington: “Scientists can now control thermal profiles at the nanoscale” 

    U Washington

    From University of Washington

    August 9, 2019
    James Urton

    1
    Handwritten notes from David J. Masiello, associate professor of chemistry at the University of WashingtonDavid J. Masiello / U. of Washington

    At human scale, controlling temperature is a straightforward concept. Turtles sun themselves to keep warm. To cool a pie fresh from the oven, place it on a room-temperature countertop.

    At the nanoscale — at distances less than 1/100th the width of the thinnest human hair — controlling temperature is much more difficult. Nanoscale distances are so small that objects easily become thermally coupled: If one object heats up to a certain temperature, so does its neighbor.

    When scientists use a beam of light as that heat source, there is an additional challenge: Thanks to heat diffusion, materials in the beam path heat up to approximately the same temperature, making it difficult to manipulate the thermal profiles of objects within the beam. Scientists have never been able to use light alone to actively shape and control thermal landscapes at the nanoscale.

    At least, not until now.

    In a paper published online July 30 by the journal ACS Nano, a team of researchers reports that they have designed and tested an experimental system that uses a near-infrared laser to actively heat two gold nanorod antennae — metal rods designed and built at the nanoscale — to different temperatures. The nanorods are so close together that they are both electromagnetically and thermally coupled. Yet the team, led by researchers at the University of Washington, Rice University and Temple University, measured temperature differences between the rods as high as 20 degrees Celsius. By simply changing the wavelength of the laser, they could also change which nanorod was cooler and which was warmer, even though the rods were made of the same material.

    “If you put two similar objects next to each other on a table, ordinarily you would expect them to be at the same temperature. The same is true at the nanoscale,” said lead corresponding author David Masiello, a UW professor of chemistry and faculty member in both the Molecular & Engineering Sciences Institute and the Institute for Nano-Engineered Systems. “Here, we can expose two coupled objects of the same material composition to the same beam, and one of those objects will be warmer than the other.”

    Masiello’s team performed the theoretical modeling to design this system. He partnered with co-corresponding authors Stephan Link, a professor of both chemistry and electrical and computer engineering at Rice University, and Katherine Willets, an associate professor of chemistry at Temple University, to build and test it.

    Their system consisted of two nanorods made of gold — one 150 nanometers long and the other 250 nanometers long, or about 100 times thinner than the thinnest human hair. The researchers placed the nanorods close together, end to end on a glass slide surrounded by glycerol.

    2
    This figure shows evidence that the two nanorods were heated to different temperatures. The researchers collected data on how the heated nanorods and surrounding glycerol scattered photons from a beam of green light. The five graphs show the intensity of that scattered light at five different wavelengths, and insets show images of the scattered light. Arrows indicate that peak intensity shifts at different wavelengths, an indirect sign that the nanorods were heated to different temperatures.Bhattacharjee et al., ACS Nano, 2019.

    They chose gold for a specific reason. In response to sources of energy like a near-infrared laser, electrons within gold can “oscillate” easily. These electronic oscillations, or surface plasmon resonances, efficiently convert light to heat. Though both nanorods were made of gold, their differing size-dependent plasmonic polarizations meant that they had different patterns of electron oscillations. Masiello’s team calculated that, if the nanorod plasmons oscillated with either the same or opposite phases, they could reach different temperatures — countering the effects of thermal diffusion.

    Link’s and Willets’ groups designed the experimental system and tested it by shining a near-infrared laser on the nanorods. They studied the beam’s effect at two wavelengths — one for oscillating the nanorod plasmons with the same phase, another for the opposite phase.

    The team could not directly measure the temperature of each nanorod at the nanoscale. Instead, they collected data on how the heated nanorods and surrounding glycerol scattered photons from a separate beam of green light. Masiello’s team analyzed those data and discovered that the nanorods refracted photons from the green beam differently due to nanoscale differences in temperature between the nanorods.

    “This indirect measurement indicated that the nanorods had been heated to different temperatures, even though they were exposed to the same near-infrared beam and were close enough to be thermally coupled,” said co-lead author Claire West, a UW doctoral candidate in the Department of Chemistry.

    The team also found that, by changing the wavelength of near-infrared light, they could change which nanorod — short or long — heated up more. The laser could essentially act as a tunable “switch,” changing the wavelength to alter which nanorod was hotter. The temperature differences between the nanorods also varied based on their distance apart, but reached as high as 20 degrees Celsius above room temperature.

    The team’s findings have a range of applications based on controlling temperature at the nanoscale. For example, scientists could design materials that photo-thermally control chemical reactions with nanoscale precision, or temperature-triggered microfluidic channels for filtering tiny biological molecules.

    The researchers are working to design and test more complex systems, such as clusters and arrays of nanorods. These require more intricate modeling and calculations. But given the progress to date, Masiello is optimistic that this unique partnership between theoretical and experimental research groups will continue to make progress.

    “It was a team effort, and the results were years in the making, but it worked,” said Masiello.

    West’s co-lead authors on the paper are Ujjal Bhattacharjee, a former researcher at Rice University now at the Indian Institute of Engineering Science and Technology, Shibpur, and Seyyed Ali Hosseini Jebeli, a researcher at Rich University. Co-authors are Harrison Goldwyn and Elliot Beutler, both doctoral students in the UW Department of Chemistry; Xiang-Tian Kong and Zhongwei Hu, both research associates in the UW Department of Chemistry; and Wei-Shun Chang, a former research scientist at Rice, now an assistant professor of chemistry and biochemistry at the University of Massachusetts Dartmouth. The research was funded by the National Science Foundation, the Robert A. Welch Foundation, and the University of Washington.

    For more information, contact Masiello at 206-543-5579 or masiello@uw.edu.

    See the full article here .


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    So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
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