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News Article | July 7, 2017
Site: www.materialstoday.com

A team of researchers at the US Department of Energy's (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. This nickel oxide compound does not actually superconduct, said John Mitchell, associate director of the laboratory's Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy and computational theory. But, he added, "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." Mitchell and seven co-authors report their results in a paper in Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, power grids that can transmit electricity without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that superconduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, the discovery of high-temperature superconductivity in copper oxide compounds known as cuprates suggested new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates. Nickel-based oxides – nickelates – have long been considered as potential cuprate analogs because nickel sits immediately adjacent to copper in the periodic table. Thus far, Mitchell noted, "that's been an unsuccessful quest". As he and his co-authors noted in their Nature Physics paper: "None of these analogs have been superconducting, and few are even metallic." The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning it comprises three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. "Thus it looks more two-dimensional than three-dimensional, structurally and electronically," Mitchell said. This nickelate shares its quasi-two-dimensional trilayer structure with a similar compound containing lanthanum rather than praseodymium. But the lanthanum analog is non-metallic and adopts a so-called ‘charge-stripe’ phase, an electronic property that makes the material an insulator, the opposite of a superconductor. "For some yet-unknown reason, the praseodymium system does not form these stripes," Mitchell said. "It remains metallic and so is certainly the more likely candidate for superconductivity." Argonne is one of a few laboratories in the world where the compound could be created, thanks to the special abilities of the Materials Science Division's high-pressure optical-image floating zone furnace. This furnace can attain pressures of 150 atmospheres (equivalent to the crushing pressures found at oceanic depths of nearly 5000 feet) and temperatures of approximately 2000°C, just the conditions needed to grow the crystals. "We didn't know for sure we could make these materials," said Argonne postdoctoral researcher Junjie Zhang, first author on the study. But they were able to grow nickelate crystals measuring a few millimeters in diameter (a small fraction of an inch). The research team verified that the electronic structure of the nickelate resembles that of cuprate materials by taking X-ray absorption spectroscopy measurements at the Advanced Photon Source, a DOE Office of Science User Facility, and by performing density functional theory calculations. Materials scientists use density functional theory to investigate the electronic properties of condensed matter systems. "I've spent my entire career not making high-temperature superconductors," Mitchell joked. But that could change in the next phase of his team's research: attempting to induce superconductivity in their nickelate material using a chemical process called electron doping, in which impurities are deliberately added to a material to influence its properties. This story is adapted from material from Argonne National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." This nickel oxide compound does not superconduct, said John Mitchell, an Argonne Distinguished Fellow and associate director of the laboratory's Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy, and computational theory. But, he added, "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." Mitchell and seven co-authors announced their results in this week's issue of Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, grids that can transmit power without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that superconduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, discovery of high-temperature superconductivity in copper oxide compounds called cuprates engendered new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates. Nickel-based oxides - nickelates - have long been considered as potential cuprate analogs because the element sits immediately adjacent to copper in the periodic table. Thus far, Mitchell noted, "That's been an unsuccessful quest." As he and his co-authors noted in their Nature Physics paper, "None of these analogs have been superconducting, and few are even metallic." The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning that it consists of three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. "Thus it looks more two-dimensional than three-dimensional, structurally and electronically," Mitchell said. This nickelate and a compound containing lanthanum rather than praseodymium both share the quasi-two-dimensional trilayer structure. But the lanthanum analog is non-metallic and adopts a so-called "charge-stripe" phase, an electronic property that makes the material an insulator, the opposite of a superconductor. "For some yet-unknown reason, the praseodymium system does not form these stripes," Mitchell said. "It remains metallic and so is certainly the more likely candidate for superconductivity." Argonne is one of a few laboratories in the world where the compound could be created. The Materials Science Division's high-pressure optical-image floating zone furnace has special capabilities. It can attain pressures of 150 atmospheres (equivalent to the crushing pressures found at oceanic depths of nearly 5,000 feet) and temperatures of approximately 2,000 degrees Celsius (more than 3,600 degrees Fahrenheit), conditions needed to grow the crystals. "We didn't know for sure we could make these materials," said Argonne postdoctoral researcher Junjie Zhang, the first author on the study. But indeed, they managed to grow the crystals measuring a few millimeters in diameter (a small fraction of an inch). The research team verified that the electronic structure of the nickelate resembles that of cupratematerials by taking X-ray absorption spectroscopy measurements at the Advanced Photon Source, a DOE Office of Science User Facility, and by performing density functional theory calculations. Materials scientists use density functional theory to investigate the electronic properties of condensed matter systems. "I've spent my entire career not making high-temperature superconductors," Mitchell joked. But that could change in the next phase of his team's research: attempting to induce superconductivity in their nickelate material using a chemical process called electron doping, in which impurities are deliberately added to a material to influence its properties. Explore further: Surprising stripes in a 'bad metal' offer clues to high-temperature superconductivity More information: Junjie Zhang et al, Large orbital polarization in a metallic square-planar nickelate, Nature Physics (2017). DOI: 10.1038/nphys4149


A team of researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. This nickel oxide compound does not superconduct, said John Mitchell, an Argonne Distinguished Fellow and associate director of the laboratory’s Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy, and computational theory. But, he added, “It’s poised for superconductivity in a way not found in other nickel oxides. We’re very hopeful that all we have to do now is find the right electron concentration.” Mitchell and seven co-authors announced their results in this week’s issue of Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, grids that can transmit power without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that superconduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, discovery of high-temperature superconductivity in copper oxide compounds called cuprates engendered new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates. Nickel-based oxides – nickelates – have long been considered as potential cuprate analogs because the element sits immediately adjacent to copper in the periodic table. Thus far, Mitchell noted, “That’s been an unsuccessful quest.” As he and his co-authors noted in their Nature Physics paper, “None of these analogs have been superconducting, and few are even metallic.” The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning that it consists of three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. “Thus it looks more two-dimensional than three-dimensional, structurally and electronically,” Mitchell said. This nickelate and a compound containing lanthanum rather than praseodymium both share the quasi-two-dimensional trilayer structure. But the lanthanum analog is non-metallic and adopts a so-called “charge-stripe” phase, an electronic property that makes the material an insulator, the opposite of a superconductor. “For some yet-unknown reason, the praseodymium system does not form these stripes,” Mitchell said. “It remains metallic and so is certainly the more likely candidate for superconductivity.” Argonne is one of a few laboratories in the world where the compound could be created. The Materials Science Division’s high-pressure optical-image floating zone furnace has special capabilities. It can attain pressures of 150 atmospheres (equivalent to the crushing pressures found at oceanic depths of nearly 5,000 feet) and temperatures of approximately 2,000 degrees Celsius (more than 3,600 degrees Fahrenheit), conditions needed to grow the crystals. “We didn’t know for sure we could make these materials,” said Argonne postdoctoral researcher Junjie Zhang, the first author on the study. But indeed, they managed to grow the crystals measuring a few millimeters in diameter (a small fraction of an inch). The research team verified that the electronic structure of the nickelate resembles that of cuprate materials by taking X-ray absorption spectroscopy measurements at the Advanced Photon Source, a DOE Office of Science User Facility, and by performing density functional theory calculations. Materials scientists use density functional theory to investigate the electronic properties of condensed matter systems. “I’ve spent my entire career not making high-temperature superconductors,” Mitchell joked. But that could change in the next phase of his team’s research: attempting to induce superconductivity in their nickelate material using a chemical process called electron doping, in which impurities are deliberately added to a material to influence its properties. For the original study published in Nature Physics, see “Large orbital polarization in a metallic square-planar nickelate.” Other Argonne authors included Materials Science Division scientists Antia Botana, Daniel Phelan, Hong Zheng, Michael Norman, and John Freeland of the Advanced Photon Source; the other author was Victor Pardo of the University of Santiago de Compostela in Spain. Funding was provided by the U.S. Department of Energy, Office of Science and the National Science Foundation.


News Article | June 16, 2017
Site: www.eurekalert.org

A team of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." This nickel oxide compound does not superconduct, said John Mitchell, an Argonne Distinguished Fellow and associate director of the laboratory's Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy, and computational theory. But, he added, "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." Mitchell and seven co-authors announced their results in this week's issue of Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, grids that can transmit power without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that superconduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, discovery of high-temperature superconductivity in copper oxide compounds called cuprates engendered new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates. Nickel-based oxides - nickelates - have long been considered as potential cuprate analogs because the element sits immediately adjacent to copper in the periodic table. Thus far, Mitchell noted, "That's been an unsuccessful quest." As he and his co-authors noted in their Nature Physics paper, "None of these analogs have been superconducting, and few are even metallic." The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning that it consists of three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. "Thus it looks more two-dimensional than three-dimensional, structurally and electronically," Mitchell said. This nickelate and a compound containing lanthanum rather than praseodymium both share the quasi-two-dimensional trilayer structure. But the lanthanum analog is non-metallic and adopts a so-called "charge-stripe" phase, an electronic property that makes the material an insulator, the opposite of a superconductor. "For some yet-unknown reason, the praseodymium system does not form these stripes," Mitchell said. "It remains metallic and so is certainly the more likely candidate for superconductivity." Argonne is one of a few laboratories in the world where the compound could be created. The Materials Science Division's high-pressure optical-image floating zone furnace has special capabilities. It can attain pressures of 150 atmospheres (equivalent to the crushing pressures found at oceanic depths of nearly 5,000 feet) and temperatures of approximately 2,000 degrees Celsius (more than 3,600 degrees Fahrenheit), conditions needed to grow the crystals. "We didn't know for sure we could make these materials," said Argonne postdoctoral researcher Junjie Zhang, the first author on the study. But indeed, they managed to grow the crystals measuring a few millimeters in diameter (a small fraction of an inch). The research team verified that the electronic structure of the nickelate resembles that of cuprate materials by taking X-ray absorption spectroscopy measurements at the Advanced Photon Source, a DOE Office of Science User Facility, and by performing density functional theory calculations. Materials scientists use density functional theory to investigate the electronic properties of condensed matter systems. "I've spent my entire career not making high-temperature superconductors," Mitchell joked. But that could change in the next phase of his team's research: attempting to induce superconductivity in their nickelate material using a chemical process called electron doping, in which impurities are deliberately added to a material to influence its properties. For the original study published in Nature Physics, see "Large orbital polarization in a metallic square-planar nickelate." Other Argonne authors included Materials Science Division scientists Antia Botana, Daniel Phelan, Hong Zheng, Michael Norman, and John Freeland of the Advanced Photon Source; the other author was Victor Pardo of the University of Santiago de Compostela in Spain. Funding was provided by the U.S. Department of Energy, Office of Science and the National Science Foundation. Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science. The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit the Office of Science website.


News Article | June 17, 2017
Site: www.sciencedaily.com

A team of researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory has identified a nickel oxide compound as an unconventional but promising candidate material for high-temperature superconductivity. The team successfully synthesized single crystals of a metallic trilayer nickelate compound, a feat the researchers believe to be a first. "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." This nickel oxide compound does not superconduct, said John Mitchell, an Argonne Distinguished Fellow and associate director of the laboratory's Materials Science Division, who led the project, which combined crystal growth, X-ray spectroscopy, and computational theory. But, he added, "It's poised for superconductivity in a way not found in other nickel oxides. We're very hopeful that all we have to do now is find the right electron concentration." Mitchell and seven co-authors announced their results in this week's issue of Nature Physics. Superconducting materials are technologically important because electricity flows through them without resistance. High-temperature superconductors could lead to faster, more efficient electronic devices, grids that can transmit power without energy loss and ultra-fast levitating trains that ride frictionless magnets instead of rails. Only low-temperature superconductivity seemed possible before 1986, but materials that superconduct at low temperatures are impractical because they must first be cooled to hundreds of degrees below zero. In 1986, however, discovery of high-temperature superconductivity in copper oxide compounds called cuprates engendered new technological potential for the phenomenon. But after three decades of ensuing research, exactly how cuprate superconductivity works remains a defining problem in the field. One approach to solving this problem has been to study compounds that have similar crystal, magnetic and electronic structures to the cuprates. Nickel-based oxides -- nickelates -- have long been considered as potential cuprate analogs because the element sits immediately adjacent to copper in the periodic table. Thus far, Mitchell noted, "That's been an unsuccessful quest." As he and his co-authors noted in their Nature Physics paper, "None of these analogs have been superconducting, and few are even metallic." The nickelate that the Argonne team has created is a quasi-two-dimensional trilayer compound, meaning that it consists of three layers of nickel oxide that are separated by spacer layers of praseodymium oxide. "Thus it looks more two-dimensional than three-dimensional, structurally and electronically," Mitchell said. This nickelate and a compound containing lanthanum rather than praseodymium both share the quasi-two-dimensional trilayer structure. But the lanthanum analog is non-metallic and adopts a so-called "charge-stripe" phase, an electronic property that makes the material an insulator, the opposite of a superconductor. "For some yet-unknown reason, the praseodymium system does not form these stripes," Mitchell said. "It remains metallic and so is certainly the more likely candidate for superconductivity." Argonne is one of a few laboratories in the world where the compound could be created. The Materials Science Division's high-pressure optical-image floating zone furnace has special capabilities. It can attain pressures of 150 atmospheres (equivalent to the crushing pressures found at oceanic depths of nearly 5,000 feet) and temperatures of approximately 2,000 degrees Celsius (more than 3,600 degrees Fahrenheit), conditions needed to grow the crystals. "We didn't know for sure we could make these materials," said Argonne postdoctoral researcher Junjie Zhang, the first author on the study. But indeed, they managed to grow the crystals measuring a few millimeters in diameter (a small fraction of an inch). The research team verified that the electronic structure of the nickelate resembles that of cuprate materials by taking X-ray absorption spectroscopy measurements at the Advanced Photon Source, a DOE Office of Science User Facility, and by performing density functional theory calculations. Materials scientists use density functional theory to investigate the electronic properties of condensed matter systems. "I've spent my entire career not making high-temperature superconductors," Mitchell joked. But that could change in the next phase of his team's research: attempting to induce superconductivity in their nickelate material using a chemical process called electron doping, in which impurities are deliberately added to a material to influence its properties.


News Article | June 5, 2017
Site: www.nanotech-now.com

Abstract: Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion Zhenhua Zeng1, Kee-Chul Chang2, Joseph Kubal1, Nenad M. Markovic2 and Jeffrey Greeley1 1 School of Chemical Engineering, Purdue University, West Lafayette, Indiana 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois Design of cost-effective electrocatalysts with enhanced stability and activity is of paramount importance for the next generation of energy conversion systems, including fuel cells and electrolysers. However, electrocatalytic materials generally improve one of these properties at the expense of the other. Here, using density functional theory calculations and electrochemical surface science measurements, we explore atomic-level features of ultrathin (hydroxy)oxide films on transition metal substrates and demonstrate that these films exhibit both excellent stability and activity for electrocatalytic applications. The films adopt structures with stabilities that significantly exceed bulk Pourbaix limits, including stoichiometries not found in bulk and properties that are tunable by controlling voltage, film composition, and substrate identity. Using nickel (hydroxy)oxide/Pt(111) as an example, we further show how the films enhance activity for hydrogen evolution through a bifunctional effect. The results suggest design principles for this class of electrocatalysts with simultaneously enhanced stability and activity for energy conversion. Purdue University scientists' simulations have unraveled the mystery of a new electrocatalyst that may solve a significant problem associated with fuel cells and electrolyzers. Fuel cells, which use chemical reactions to produce energy, and electrolyzers, which convert energy into hydrogen or other gases, use electrocatalysts to promote chemical reactions. Electrocatalysts that can activate such reactions tend to be unstable because they can corrode in the highly acidic or basic water solutions that are used in fuel cells or electrolyzers. A team led by Jeffrey Greeley, an associate professor of chemical engineering, has identified the structure for an electrocatalyst made of nickel nanoislands deposited on platinum that is both active and stable. This design created properties in the nickel that Greeley said were unexpected but highly beneficial. "The reactions led to very stable structures that we would not predict by just looking at the properties of nickel," Greeley said. "It turned out to be quite a surprise." Greeley's team and collaborators working at Argonne National Laboratory had noticed that nickel placed on a platinum substrate showed potential as an electrocatalyst. Greeley's lab then went to work to figure out how an electrocatalyst with this composition could be both active and stable. Greeley's team simulated different thicknesses and diameters of nickel on platinum as well as voltages and pH levels in the cells. Placing nickel only one or two atomic layers in thickness and one to two nanometers in diameter created the conditions they wanted. "They're like little islands of nickel sitting on a sea of platinum," Greeley said. The ultra-thin layer of nickel is key, Greeley said, because it's at the point where the two metals come together that all the electrochemical activity occurs. And since there are only one or two atomic layers of nickel, almost all of it is reacting with the platinum. That not only creates the catalysis needed, but changes the nickel in a way that keeps it from oxidizing, providing the stability. Collaborators at Argonne then analyzed the nickel-platinum structure and confirmed the properties Greeley and his team expected the electrocatalyst to have. Next, Greeley plans to test similar structures with different metals, such as replacing platinum with gold or the nickel with cobalt, as well as modifying pH and voltages. He believes other more stable and active combinations may be found using his computational analysis. ### The U.S. Department of Energy supported the research. The research was published in May by the journal Nature Energy. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | February 15, 2017
Site: www.spie.org

From the SPIE Photonics West Show Daily : Three plenary speakers at LASE 2017 discussed the LIGO discovery of gravitational waves in space, laser-based direct-write methods, and high-power EUV light sources for lithography. For more than a quarter of a century, Karsten Danzmann has dedicated his career to developing technology that could expand our understanding of the universe by detecting gravitational waves emanating from exotic objects in space. On September 14, 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) finally did just that. For the first time, US LIGO detectors in Livingston, LA, and Hanford, WA, heard the first "peep" from an event in the distant universe — in this case the collision of two black holes. The event confirmed a major prediction of Albert Einstein's 1915 general theory of relativity and opened a new window into the cosmos. It was such a major breakthrough that it took several days for the LIGO team to accept that it might actually be real, according to Danzmann, director of the Max Planck Institute for Gravitational Physics, a member of the LIGO Scientific Collaboration. And it was another five months before they made their findings public. "I've been chasing this for 27 years, and when it finally happened it was unbelievable," said Danzmann, who noted that a second, similar event, the detection of gravitational waves produced by two black holes colliding 1.4 billion light years away, was captured in June 2016 at the same two observatories. "We've been looking at the universe with our eyes for thousands of years, and we know it looks very different depending on whether we look at it with visible light, infrared light, gamma rays, xrays, ... but we haven't been able to hear it. And suddenly now we can. And we have hope that the dark side of the universe, which makes up 99% of the universe, is now accessible to us." During the LASE plenary session at SPIE Photonics West 2017 in February, Danzmann's enthusiasm was contagious as he described the developments leading up to that historic moment, from the physics and technology to the thousands of people involved worldwide for decades (the first published paper, in Physics Review Letters, listed 1004 authors from 133 institutions). For Danzmann, one of the key turning points came when Advanced LIGO, a $200 million upgrade to LIGO, was unveiled in mid-2015. With the upgrade, which took five years to complete, the observatories are now 10 times more sensitive than their predecessors, thanks to advances in the optical layout, new high-power (165W) stabilized laser systems, advanced mirror suspension, and improved pre-isolation for detecting very low frequencies, according to Danzmann. "The upgrade to Advanced LIGO was drastic," Danzmann said. "The building is still the same, and the stainless steel of vacuum tubes are the same, but everything else has changed." Danzmann is equally excited about a more recent development: LISA Pathfinder, a satellite mission launched in December 2015 whose payload includes the first laser interferometer in space. "On the ground we are listening to the high frequencies of the universe, but if we want to listen to low frequencies, we have to go into space," said Danzmann, who is co-principal investigator on the LISA technology package. "Some of the most interesting things in the universe are supermassive black holes. When galaxies collide, which happens all the time, these super black holes merge and emit a huge signal, and that is what we want to listen to in space." Another LASE plenary talk featured an overview of the current state-of-the-art in using laser-based direct-write (LDW) methods to print hybrid electronics. The talk was given by Alberto Pique, acting head of the Materials and Sensor Branch of the Materials Science Division at the US Naval Research Laboratory. "The goal is very simple: can we go from a design to a printed part that is not faithful in a structural sense but in a functional sense?" Pique posited. "To do that, we need a substrate, we need to wire it up, place the devices, then connect the wires and devices. If you do it right, you end up with a functional circuit." This is where additive manufacturing (AM) comes in. AM is considered a game changer for design and fabrication of 3D parts by reducing the number of steps from concept to part, while direct-write processes make it possible to fabricate custom electronics in less time and at lower cost than other techniques. Combining the two paves the way for more efficient and cost-effective printing of hybrid electronics. The ability of LDW to deposit functional materials over a wide viscosity range onto many diverse surfaces makes it unique among direct write processes, Pique noted. For example, when manufacturing inkjet nozzles, "you have to be careful about the material you put on the nozzle and you have to worry about the nature of the fluid. But when you use the LDW forward transfer technique, the nature of material is not that critical." Advances in lasers, materials, and positioning have spurred the development of LDW in AM, he added. In particular, the availability of high-repetition rate solid-state UV lasers with stable, moderate energies has allowed LDW to deposit materials rapidly in all three dimensions. By comparison, low-rep rate UV lasers with more uniform beam profiles have enabled printing larger area voxels, which also speeds up the LDW process. "Over the years, we have shown that with LDW we can both add and remove material, and this gives the laser technique an edge (over other direct-write techniques) because you can do two things with the same set up," Pique said. "The same system performs both additive and subtractive processes." In the final LASE plenary talk, Hakaru Mizoguchi, executive vice president of Gigaphoton, provided an update on the company's efforts to develop high-power EUV light sources for high-volume manufacturing (HVM) lithography. In July 2016, Gigaphoton demonstrated 250W light output at 4% conversion efficiency with a laser-produced plasma (LPP) light source prototype for EUV scanners. Since then, Gigaphoton has continued to test and refine its EUV light sources, with a goal of eventually reaching 500W, according to Mizoguchi. Photolithography equipment manufacturers are keen for a 250W power EUV source to deliver the kind of wafer productivity throughput their customers demand. To achieve these powers, Gigaphoton uses a dual-laser "priming" pulse from a yv04 (vanadate) laser ahead of a nanosecond-duration carbon dioxide blast, plus sub 20 μm micro droplet supply technology, proprietary energy control technology, and magnetic field-enabled debris mitigation technology. In anticipation of introducing these systems to the commercial market, the company is preparing to move into a new headquarters in Japan that doubles its office space and provides 1.5 times the production space, Mizoguchi noted. Symposium chairs for LASE 2017 were SPIE Fellows Koji Sugioka of RIKEN (Japan) and Reinhart Poprawe of Fraunhofer-Institut für Lasertechnik (Germany). Cochairs were SPIE Fellow Yongfeng Lu of University of Nebraska, Lincoln (USA), and Guido Hennig of Daetwyler Graphics (Switzerland). Photonics West 2017, 28 January through 2 February at the Moscone Center in San Francisco, CA (USA), encompassed more than 4700 presentations on light-based technologies across more than 95 conferences. It was also the venue for dozens of technical courses for professional development, the Prism Awards for Photonics Innovation, the SPIE Startup Challenge, a two-day job fair, two major exhibitions, and a diverse business program with more than 25 events. SPIE Photonics West 2018 will run 27 January through 1 February at Moscone Center.


News Article | January 21, 2016
Site: www.rdmag.com

Lawrence Livermore National Laboratory researchers have created a library of nanoporous gold structures on a single chip that has direct applications for high-capacity lithium ion batteries as well as neural interfaces. Nanoporous gold (np-Au), a porous metal used in energy and biomedical research, is produced through an alloy corrosion process known as dealloying that generates a characteristic three-dimensional nanoscale network of pores and ligaments. In the cover article in the Jan. 14 issue of Nanoscale(link is external), a journal published by the Royal Society of Chemistry, LLNL researchers and their University of California, Davis(link is external) collaborators describe a method for creating a library of varying np-Au morphologies on a single chip via precise delivery of tunable laser energy. UC Davis professor Erkin Seker served as the principal investigator (PI) of the UC Fees project that primarily funded the work, along with co-PI Monika Biener of LLNL’s Materials Science Division. Laser microprocessing (e.g. micromachining) provides spatial and temporal control while imposing energy near the surface of the material. “Traditional heat application techniques for the modification of np-Au are bulk processes that cannot be used to generate a library of different pore sizes on a single chip,” said LLNL staff scientist Ibo Matthews, co-author of the paper. “Laser microprocessing offers an attractive solution to this problem by providing a means to apply energy with high spatial and temporal resolution.” The researchers used multiphysics simulations to predict the effects of continuous wave vs. pulsed laser mode and varying thermal conductivity of the supporting substrate on the local np-Au film temperatures during photothermal annealing. They were then able to fabricate an on-chip material library consisting of 81 np-Au samples of nine different morphologies for use in the parallel study of structure–property relationships. “These libraries have the potential to drastically increase the throughput of morphology interaction studies for np-Au, specifically in applications such as high capacity lithium ion batteries, cell-material interaction studies for neural interfaces, analytical biosensors, as well as nanoscale material science studies,” said Biener, co-author of the paper. This work sets the foundation for understanding laser-based annealing of porous thin film materials. The fabrication of single chip material libraries has the potential to increase the throughput of material interaction testing in many disciplines through easy single-chip material screening libraries. LLNL’s Juergen Biener of the Material Sciences Division collaborated on the work along with UC Davis researchers Christopher Chapman (lead author) and Ling Wang. This work was funded by UC Lab Fees, National Science Foundation and National Institutes of Health.


News Article | September 19, 2016
Site: www.rdmag.com

Graphene is the stuff of the future. For years, researchers and technologists have been predicting the utility of the one-atom-thick sheets of pure carbon in everything from advanced touch screens and semiconductors to long-lasting batteries and next-generation solar cells. But graphene's unique intrinsic properties – supreme electrical and thermal conductivities and remarkable electron mobility, to name just a few – can only be fully realized if it is grown free from defects that disrupt the honeycomb pattern of the bound carbon atoms. A team led by Materials Scientist Anirudha Sumant with the U.S. Department of Energy's (DOE) Argonne National Laboratory's Center for Nanoscale Materials (CNM) and Materials Science Division, along with collaborators at the University of California-Riverside, has developed a method to grow graphene that contains relatively few impurities and costs less to make, in a shorter time and at lower temperatures compared to the processes widely used to make graphene today. Theoretical work led by Argonne nanoscientist Subramanian Sankaranarayanan at the CNM helped researchers understand the molecular-level processes underlying the graphene growth. "I'd been dealing with all these different techniques of growing graphene, and you never see such a uniform, smooth surface." The new technology taps ultrananocrystalline diamond (UNCD), a synthetic type of diamond that Argonne researchers have pioneered through years of research. UNCD serves as a physical substrate, or surface on which the graphene grows, and the source for the carbon atoms that make up a rapidly produced graphene sheet. "When I first looked at the [scanning electron micrograph] and saw this nice uniform, very complete layer, it was amazing," said Diana Berman, the first author of the study and former postdoctoral research associate who worked with Sumant and is now an Assistant Professor at the University of North Texas. "I'd been dealing with all these different techniques of growing graphene, and you never see such a uniform, smooth surface." Current graphene fabrication protocols introduce impurities during the etching process itself, which involves adding acid and extra polymers, and when they are transferred to a different substrate for use in electronics. "The impurities introduced during this etching and the transferring step negatively affect the electronic properties of the graphene," Sumant said. "So you do not get the intrinsic properties of the graphene when you actually do this transfer." The team found that the single-layer, single-domain graphene can be grown over micron-size holes laterally, making them completely free-standing (that is, detached from the underlying substrate). This makes it possible to exploit the intrinsic properties of graphene by fabricating devices directly over free-standing graphene. The new process is also much more cost-effective than conventional methods based on using silicon carbide as a substrate. Sumant says that the 3- to 4-inch silicon carbide wafers used in these types of growth methods cost about $1,200, while UNCD films on silicon wafers cost less than $500 to make. The diamond method also takes less than a minute to grow a sheet of graphene, where the conventional method takes on the order of hours. The high quality of graphene was confirmed by the UC Riverside co-authors Zhong Yan and Alexander Balandin by fabricating top-gate field-effect transistors from this material and measuring its electron mobility and charge carrier concentration. "It is well known that certain metals, such as nickel and iron, dissolve diamond at elevated temperatures, and the same process has been used for many years to polish diamond," said Sumant. He and his team used this property to employ nickel in converting the top layer of diamond into amorphous carbon, but it was not clear how these freed carbon atoms converted instantly into high-quality graphene. After Sumant's and Berman's initial breakthrough of growing graphene directly on UNCD, Sankaranarayanan and his postdocs Badri Narayanan and Sanket Deshmukh, computational material scientists at the CNM used resources at the Argonne Leadership Computing Facility (ALCF) to help the team better understand the mechanism of the growth process underlying this interesting phenomenon using reactive molecular dynamic simulations. Computer simulations developed by Narayanan, Deshmukh and Sankaranarayanan showed that certain crystallographic orientation of nickel-111 highly favor nucleation, and subsequent rapid growth of graphene; this was then confirmed experimentally. These large-scale simulations also showed how graphene forms. The nickel atoms diffuse into the diamond and destroy its crystalline order, while carbon atoms from this amorphous solid move to the nickel surface and rapidly form honeycomb-like structures, resulting in mostly defect-free graphene. The nickel then percolated through the fine crystalline grains of the UNCD, sinking out of the way and removing the need for acid to dissolve away excess metal atoms from the top surface. "It is like meeting a good Samaritan at an unknown place who helps you, does his job and leaves quietly without a trace," said Sumant. "The proven predictive power of our simulations places us in a position of advantage to enable rapid discovery of new catalytic alloys that mediate growth of high-quality graphene on dielectrics and move away on their own when the growth is completed," added Narayanan. In addition to the utility in making minimally defective, application-ready graphene for things like low-frequency vibration sensors, radio frequency transistors and better electrodes for water purification, Berman and Sumant say that the Argonne team has already secured three patents arising from their new graphene growth method. The researchers have already struck a collaboration with Swedish Institute of Space Physics involving the European Space Agency for their Jupiter Icy Moons Explorer (JUICE) program to develop graphene-coated probes that may help exploratory vehicles sense the properties of plasma surrounding the moons of Jupiter. Closer to home, the team has also crafted diamond and graphene needles for researchers at North Carolina University to use in biosensing applications. The Argonne researchers are now fine-tuning the process – tweaking the temperature used to catalyze the reaction and adjusting the thickness of the diamond substrate and the composition of the metal film that facilitates the graphene growth – to both optimize the reaction and to better study the physics at the graphene-diamond interface. "We're trying to tune this more carefully to have a better understanding of which conditions lead to what quality of graphene we're seeing," Berman said. Other Argonne authors involved in the study were Alexander Zinovev and Daniel Rosenmann. The paper, "Metal-induced rapid transformation of diamond into single and multilayer graphene on wafer scale," is published inNature Communications.


News Article | February 20, 2017
Site: phys.org

The process of electrophoretic deposition (EPD) uses an electric field to drive colloidal particles suspended in a liquid from a solution onto a conductive substrate. Commonly used to apply paint to cars, EPD also is utilized to coat ceramics, metals and polymers with a range of materials and for 3-D printing objects. Developed using a particle dynamics framework and run on the Vulcan supercomputing system at LLNL, the newly published model tracks every single particle during the entire EPD process—each particle is about 200 nanometers wide, roughly the diameter of the smallest bacteria. The research is published in the Dec. 20 issue of the journal Langmuir . "This gives us more information than any model before and fresh insights that were previously inaccessible," said the study's LLNL postdoctoral researcher Brian Giera. "Within this particle dynamics framework we were able to get really detailed information. In terms of understanding the EPD process in detail, this is a first-of-its kind." Over a period of two years, the team, led by principal investigator Todd Weisgraber, a researcher from LLNL's Materials Engineering Division, developed the model and ran several dozens of different simulations, changing the strength of the electrical field and the concentration of salt in the system. Not only does the strength of the electrical field affect the development of crystals, Giera said, but salt concentration, surprisingly, also plays a key role. Giera said the model could be used to better understand deposition kinetics, determine how fast to build and anticipate resulting crystallinity, which could impact how armor is produced, and how coatings are applied using the EPD process. "The model is poised to take on a lot of questions," Giera said. "It gives us more predictive information to optimize the system." Luis Zepeda-Ruiz, a scientist in the Lab's Materials Science Division, built the initial model containing all the essential mechanisms before Giera took over the work. He said the model can be augmented to allow for virtually any type of material, extending the science to a broad range of applications. "Our computational model can access details that are extremely difficult to observe in real experiments," Zepeda-Ruiz said. "It also can be used when experiments fail to reproduce results, when the solution ages and changes its chemistry. Now we have a pure, reproducible means for doing EPD, and that's a benefit." The model has been so well received by the scientific community that it was selected to be presented in a keynote speech by Giera at the international Electrophoretic Deposition Conferences Series held in South Korea in October. LLNL researcher Andy Pascall, an expert in EPD, helped define the model's initial parameter choices and is working on validating it for future implementation. Pascall said the model will be particularly useful to the field of photonics science, which requires precise control over crystallization. "Photonic crystallization is interesting to the scientific community in general. The way this has been done before in the lab has been through trial and error," Pascall said. "It's fair to say this is the only particle-based EPD model out there. Having a model that can be predictive allows you to run hundreds of virtual experiments that would take us months to do in the lab." Next, Giera will study how the colloidal particles re-suspend and, more importantly, tailor the model to account for particles of different sizes. Explore further: Theoretical model reveals how droplets grow around tiny particles on a surface More information: Brian Giera et al. Mesoscale Particle-Based Model of Electrophoretic Deposition, Langmuir (2017). DOI: 10.1021/acs.langmuir.6b04010

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