American Institute of Physics
American Institute of Physics
News Article | April 17, 2017
Washington, D.C., April 12, 2017 -- Particle physicist Don Lincoln is the winner of the 2017 Andrew Gemant Award, an annual prize recognizing significant contributions to the cultural, artistic or humanistic dimension of physics, the American Institute of Physics (AIP) announced today. Lincoln is currently a senior scientist at Fermi National Accelerator Laboratory in Chicago, where, in addition to conducting research, he also hosts dozens of particle physics videos for Fermilab's YouTube channel, the most popular of which has almost three million views. But Lincoln's efforts in the ways of public outreach and science communication go far beyond his Sagan-esque mini documentaries. His distinguished research career, which has led to over 1,000 publications and includes major contributions to the discoveries of the top quark and the Higgs boson, is paralleled by an extensive resume of science communication work. "We are delighted to award this year's prize to Dr. Lincoln, who has done so much for the field of particle physics, both in fundamental research and in the public eye," said Catherine O'Riordan, chief operating officer of AIP. "His accomplishments in making the world of subatomic particles accessible to so many continue to inspire the scientific community." Lincoln earned his doctorate in experimental particle physics from Rice University in 1994. Though neither of his parents had academic backgrounds or a particular interest in science, Lincoln found his passion for physics thanks to the very efforts of others, which he now emulates. "It turned out that it was the science popularizers of the '70s that helped me get so interested in science -- people like Isaac Asimov and Carl Sagan," Lincoln said. "So to a certain degree, this is simply payback. I figure there's some kid somewhere in Tennessee, Oklahoma, or wherever, who might be in a similar situation, and I'm hoping that by communicating the excitement of science, I might open their eyes to a life that they otherwise could never have imagined." In addition to the weekly Fermilab Today columns he wrote for over a decade, Lincoln has written countless articles appearing in magazines, like Scientific American and The Physics Teacher, and online publications, including the Huffington Post, CNN and the NOVA website's blog. He has authored three books for the public about particle physics and the universe, developed a Theory of Everything course for the Great Courses series, and given hundreds of lectures to a spectrum of audiences, including a TED talk. "I would like to change the culture among the scientific community," Lincoln said. "There is a long history of scientists being hesitant to do science communication because they think their colleagues won't take them seriously as being a real scientist -- and that I think is wrong-minded." Lincoln pointed out that most scientists are publicly funded and said he feels it's incumbent on them to communicate with the public because, "the public is, after all, the core support behind an awful lot of science research." "There are so many scientifically-based topics that will affect our society. Stem cells, vaccinations, climate change [...] and certainly the enormous advances in genetics, which will have a huge impact on our society over the next century. I strongly believe that scientists need to be in the forefront to try and explain what is possible and what is not possible," said Lincoln. "That's doesn't mean the scientists should say what we should do, that's a conversation for the entire country -- or world for that matter -- but the conversation should be based on scientific facts and not the clutter that we often see." The Gemant Award committee selected Lincoln for "over 20 years of enthusiastic and tireless communication of particle and cosmological physics to diverse audiences through public lectures, book, videos and articles, especially those aimed at physics educators." With more than 20 years of communication experience, Lincoln offered sage advice to those just starting in science communication. "I would like to tell the young people trying to do that who are scientists, in the beginning it's a very tough slog," Lincoln said. "It took me a couple of years to sell the first book, with lots of rejections. You just have to be aware that's part of the process. On the other hand, once you've done that, then you're in the club. And when you're in the club it becomes much, much easier. And that's when you can start having an impact." Lincoln will be presented with the award in conjunction with an invited public lecture which will be scheduled for later this year. The award includes a cash prize of $5,000 and a grant of $3,000 to further the public communication of physics at an institution of Lincoln's choice. More information about the award, which will be updated with the details of this year's award presentation, can be found here: https:/ . You can find out more about Don Lincoln and read some of his work on his website here: http://drdonlincoln. and Facebook page here: http://www. . The Andrew Gemant Award recognizes the accomplishments of a person who has made significant contributions to the cultural, artistic, or humanistic dimension of physics given annually. The award is made possible by a bequest of Andrew Gemant to the American Institute of Physics. The awardee receives a $5,000 cash award, designates an academic institution to receive a grant of $3,000 to further the public communication of physics, and is invited to deliver a public lecture in a suitable forum. ABOUT THE AMERICAN INSTITUTE OF PHYSICS The American Institute of Physics is a federation of scientific societies in the physical sciences, representing scientists, engineers, educators, and students. AIP offers authoritative information, services, and expertise in physics education and student programs, science communication, government relations, career services, statistical research in physics employment and education, industrial outreach, and history of the physical sciences. AIP publishes Physics Today, the most closely followed magazine of the physical sciences community, and is also home to the Society of Physics Students and the Niels Bohr Library and Archives. AIP owns AIP Publishing LLC, a scholarly publisher in the physical and related sciences. http://www.
News Article | April 26, 2017
An important concept in future healthcare is the development of devices called “lab on a chip.” These “chips,” not related to the electronic ones found in computers, are small devices in which biological fluids – blood or urine for example – are injected to fill specifically designed microscopic channels. These channels would contain biosensors which could detect for example specific markers for diseases within the fluid and provide a quick diagnosis. A large array of analyses could be performed on a device a few centimeters square. However, an arising issue is the size of the fluid sample injected inside the chip, with tiny volumes down to a billionth of a liter. Due to lack of available technologies, researchers do not yet fully understand how fluids – particularly complex ones of biological origins - behave at such small scales. Prof. Amy Shen and her team members from the Micro/Bio/Nanofluidics Unit at OIST have focused their efforts on using microfluidics as a tool to reveal the laws and principles ruling the behavior of complex fluids at the microscopic scale. Then in a second phase, they make use of these discoveries to provide direct applications in healthcare and biotechnology. Their recent findings can be found in the Journal of Rheology from the American Institute of Physics. Characterizing the Behavior of Polymer Solutions at the Microscopic Scale Polymers are large molecules built from many repeated similar units. They are omnipresent in everyday life, making up most of the synthetic materials that we use, from fabrics to rubber and polystyrene. Liquid polymer solutions can be found in many commercial items from household cleaning products to paint. But it is at the microscopic scale that polymer solutions could drastically improve diagnostic tools. “When you add a polymer to a suspension of particles in water, you trigger a new phenomenon in the microfluidic channel,” Dr. Del Giudice explained. “These polymers start acting as springs to kick particles or cells in the suspension, pushing them towards the middle of the channel and promoting their alignment.” Being able to arrange particles or cells within a microscopic channel represents a huge improvement for the use of biosensors in healthcare diagnosis. Polymer solutions could even separate and sort out by size different components in a complex biological fluid - for example blood, composed of cells and aggregates of many sizes – within a single microfluidic chip. But this phenomenon is highly dependent on the nature of the polymer itself. It takes time for the polymer in a dilute solution to return to its original shape after it being deformed by the flow. This delay, called the relaxation time, is a critical parameter to measure in order to describe polymer behavior. Today, current techniques to measure relaxation times are limited by the sensitivity of the available commercial instruments, which are only able to measure relatively long relaxation times such as those of concentrated polymer solutions in large volumes. In their work, Dr. Francesco Del Giudice and Dr. Simon Haward designed microfluidic devices to observe polymer deformation and relaxation within micrometer-wide channels. These platforms enable researchers to stretch or shear polymers at will using low volumes and low concentrations and to record the reactions to those forces. In this way, they can characterize dilute polymeric fluids with even very short relaxation times, and thus have a much better idea of their behavior at the microscopic scale. Using these new microfluidic tools would allow researchers to generate a catalogue of diverse polymeric fluids whose relaxation times are known. With such a database at their disposal, scientists could then pick a polymer appropriate for the alignment and/or separation of molecules within the biological fluid they want to study inside their chip. “This way, understanding polymer solutions will allow you to create a high throughput platform on a chip made of several different modules, each performing different analyses,” added Dr. Del Giudice.
News Article | April 26, 2017
The number of women receiving US physics PhDs is at an all-time high, according to the latest trend data from the American Institute of Physics (AIP) in College Park, Maryland. AIP figures show that in 2015, 365 women received PhDs, accounting for one in five of the total awarded. In 1975, just 47 physics doctorates (about 5% of the total) were conferred on women. By 2004, that number had risen to 175, about 16% of the total. The AIP's statistical research centre also examined primary sources of financial support for students who began physics graduate programmes in 2013 and 2014. It found that 1% of PhD students funded themselves, compared with 35% of master's students, and that 52% of PhD students worked as teaching assistants to support themselves financially. Another AIP report listed the skills most used by bachelor's graduates who pursued careers in science, technology, engineering and maths. The top skills cited by respondents were solving technical problems (97%), team working (95%), technical writing (79%), project management and quality control (both 77%), and programming (76%). Just one in five were asked to manage budgets.
News Article | July 21, 2017
Home > Press > Pulses of electrons manipulate nanomagnets and store information: Scientists use electron pulses to create and manipulate nanoscale magnetic excitations that can store data Abstract: Magnets and magnetic phenomena underpin the vast majority of modern data storage, and the measurement scales for research focused on magnetic behaviors continue to shrink with the rest of digital technology. Skyrmions, for example, are a kind of nanomagnet, comprised of a spin-correlated ensemble of electrons acting as a topological magnet on certain microscopic surfaces. The precise properties, like spin orientation, of such nanomagnets can store information. But how might you go about moving or manipulating these nanomagnets at will to store the data you want? New research from a German-U.S. collaboration now demonstrates such read/write ability using bursts of electrons, encoding topological energy structures robustly enough for potential data storage applications. As the group reports this week in Applied Physics Letters, from AIP Publishing, the magnetization of these ensemble excitations, or quasiparticles, is controlled by tailoring the profile of the electron pulses, varying either the total number of electrons or their width in space. "The work shows how magnetization of nanoscale magnets can be steered by intense ultrashort electron pulses," said Alexander Schäffer, a doctoral student at Martin-Luther-Universität Halle-Wittenberg in Halle, Germany, and lead author of the paper. "Experiments at SLAC already demonstrated the ultimate speed limit of magnetic switching with this scheme. Here we show that tailored electron pulses can swiftly write, erase or switch topologically protected magnetic textures such as skyrmions." So far, Schäffer says there are only a few realized applications of these skyrmions, which are relatively new to the forefront of solid state physics, but their properties and the current research capabilities make them ripe for next generation technologies. "In the tradition of the field of spin dynamics in nanostructures, I still appreciate the idea of non-volatile (long-term) memory devices, as the community of spintronics is also pursuing," he said. "The nice interplay between the mathematical concept of topological energy barriers and the physical transport properties of skyrmions, which are highly mobile, are the outstanding aspects for me." Not only are these magnetic excitations controllable, but the team's results confirm many of the dynamic understandings provided by theory. Moreover, their results demonstrate potential for achieving similar topological charge transcription by way of laser pulses, whose lower and mass-free energy offer a number of practical benefits. "These quasiparticles are robust against external perturbations, and hence are usually difficult to manipulate, and have a high potential for applications in data storage and computing," Schäffer said. "I was positively surprised about the nice accordance between experiment, analytics and numerical results, which gave me a good feeling in continuing this path. A second point was the finding that textures can be written with much lower beam intensity using tightly focused electron pulses. This brings their technological exploitation within reach as the required high-energy ultrafast electron microscopy setup is currently being developed at SLAC and other places worldwide." This significant step lends itself to many more in the evolution from this generation's cutting-edge research to next generation's hard drives. As they continue to build on their research, Schäffer and his collaborators are looking toward broader applicability in a number of ways. "Further development in the setups is required to be able to write skyrmionic structures on extended films, where we can't make any profit of geometric confinements like in the nanodisks," Schäffer said. "The next steps are mani-fold. Of course, an experimental realization is what we strive for with our experimental colleagues, especially the question of how good the switching-behavior between different topological states can be covered by our calculations. A complete simulation of laser-irradiated TEM of magnetic samples is one of our big goals at the moments." About American Institute of Physics Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See http://apl.aip.org . 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 | May 30, 2017
Home > Press > The synchronized dance of skyrmion spins: Computer simulations reveal new insights into skyrmion particles, which are promising for next-generation information storage and processing devices Abstract: In recent years, excitement has swirled around a type of quasi-particle called a skyrmion that arises as a collective behavior of a group of electrons. Because they're stable, only a few nanometers in size, and need just small electric currents to transport them, skyrmions hold potential as the basis for ultra-compact and energy-efficient information storage and processing devices in the future. Now, a research group in Singapore has used computer simulations to further probe the behaviors of skyrmions, gaining insight that can help scientists and engineers better study the quasi-particles in experiments. The new results, published this week in AIP Advances, from AIP Publishing, could also lead to skyrmion-based devices such as microwave nano-oscillators, used in a range of applications including wireless communication, imaging systems, radar and GPS. "Its unique attributes, for instance, could theoretically enable notebooks with hard drives the size of peanuts, and yet consume little energy," said Meng Hau Kuok of the National University of Singapore and one of the work's authors. Observed in 2009, skyrmions arise from the collective behavior of electrons in magnetic materials under certain conditions. Due to their spins, the electrons act as tiny magnets where their magnetic poles align with their spins. A phenomenon called the Dzyaloshinskii-Moriya interaction (DMI) -- which occurs at the interface between a magnetic layer and a non-magnetic metal -- tilts the spins and arranges them into circular patterns. These circular arrangements of spins, which behave collectively like particles, are skyrmions. Although researchers have studied how groups of skyrmions behave, little is known about their internal behaviors, Kuok said. In particular, physicists don't fully understand the particles' three fundamental modes, which are analogous to the fundamental vibrational modes of a guitar string corresponding to different musical notes. Like those notes, each skyrmion mode is associated with a certain frequency. "The modes can be thought of as circular patterns of spins dancing in sync," Kuok said. Understanding the modes is essential for knowing how the particles would behave. In one of the modes, called the breathing mode, the pattern of spins alternately expands and contracts. In the two other modes, the circular arrangement of spins rotates in the clockwise and counterclockwise directions, respectively. The researchers focused on a type of skyrmion called the Néel skyrmion, which exists in ultrathin films deposited on metals with a strong DMI. Using a computer, they simulated how the DMI and external magnetic fields of varying strengths affected the modes and properties of the particles. They found that given the same DMI strength, and if in the crystal phase, the frequencies corresponding to each mode depend differently on magnetic field strength. Increasing the magnetic field also induces the skyrmions to change phase relative to one another, from being arranged in ordered arrays like a crystal to randomly distributed and isolated. The researchers found that the three modes respond differently to this phase transition. Surprisingly, Kuok said, all three modes can exist in the crystal phase, while the clockwise rotational mode does not exist in the isolated phase. One reason, the simulations revealed, might be that the skyrmions are farther apart in the isolated phase than in the crystal phase. If the skyrmions are too far apart, then they can't interact. This interaction might be necessary for the clockwise rotational mode, Kuok said. Because the mode frequencies of skyrmions are in the microwave range, the quasi-particles could be used for new microwave nano-oscillators, which are important building blocks for microwave integrated circuits. A microwave nano-oscillator based on skyrmions could operate at three resonant frequencies, corresponding to the three modes. An increasing magnetic field would lower the resonant frequencies of the breathing and clockwise rotating modes at different rates, but increase the resonant frequency of the counterclockwise rotating mode. Such a skyrmion-based device would be more compact, stable, and require less energy than conventional, electron-based nano-oscillators. But before skyrmions find their way into devices, researchers still need to engineer their specific desired properties, such as size, and precisely tune their dynamic properties. "Our findings could provide theoretical insights into addressing these challenges," Kuok said. About American Institute of Physics AIP Advances is an open access journal publishing in all areas of physical sciences--applied, theoretical, and experimental. All published articles are freely available to read, download, and share. The journal prides itself on the belief that all good science is important and relevant. Our inclusive scope and publication standards make it an essential outlet for scientists in the physical sciences. 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 | July 12, 2017
Home > Press > Thinking thin brings new layering and thermal abilities to the semiconductor industry: In a breakthrough for the semiconductor industry, researchers demonstrate a new layer transfer technique called "controlled spalling" that creates many thin layers from a single gallium nitride Abstract: What would a simple technique to remove thin layers from otherwise thick, rigid semiconductor crystals mean for the semiconductor industry? This concept has been actively explored for years, as integrated circuits made on thin layers hold promise for developments including improved thermal characteristics, lightweight stackability and a high degree of flexibility compared to conventionally thick substrates. In a significant advance, a research group from IBM successfully applied their new "controlled spalling" layer transfer technique to gallium nitride (GaN) crystals, a prevalent semiconductor material, and created a pathway for producing many layers from a single substrate. As they report in the Journal of Applied Physics, from AIP Publishing, controlled spalling can be used to produce thin layers from thick GaN crystals without causing crystalline damage. The technique also makes it possible to measure basic physical properties of the material system, like strain-induced optical effects and fracture toughness, which are otherwise difficult to measure. Single-crystal GaN wafers are extremely expensive, where just one 2-inch wafer can cost thousands of dollars, so having more layers means getting more value out of each wafer. Thinner layers also provide performance advantages for power electronics, since it offers lower electrical resistance and heat is easier to remove. "Our approach to thin film removal is intriguing because it's based on fracture," said Stephen W. Bedell, research staff member at IBM Research and one of the paper's authors. "First, we first deposit a nickel layer onto the surface of the material we want to remove. This nickel layer is under tensile strength -- think drumhead. Then we simply roll a layer of tape onto the nickel, hold the substrate down so it can't move, and then peel the tape off. When we do this, the stressed nickel layer creates a crack in the underlying material that goes down into the substrate and then travels parallel to the surface." Their method boils down to simply peeling off the tape, nickel layer and a thin layer of the substrate material stuck to the nickel. "A good analogy of how remarkable this process is can be made with a pane of glass," Bedell said. "We're breaking the glass in the long direction, so instead of a bunch of broken glass shards, we're left with two full sheets of glass. We can control how much of the surface is removed by adjusting the thickness of the nickel layer. Because the entire process is done at room temperature, we can even do this on finished circuits and devices, rendering them flexible." The group's work is noteworthy for multiple reasons. For starters, it's by far the simplest method of transferring thin layers from thick substrates. And it may well be the only layer transfer method that's materially agnostic. "We've already demonstrated the transfer of silicon, germanium, gallium arsenide, gallium nitride/sapphire, and even amorphous materials like glass, and it can be applied at nearly any time in the fabrication flow, from starting materials to partially or fully finished circuits," Bedell said. Turning a parlor trick into a reliable process, working to ensure that this approach would be a consistent technique for crack-free transfer, led to surprises along the way. "The basic mechanism of substrate spalling fracture started out as a materials science problem," he said. "It was known that metallic film deposition would often lead to cracking of the underlying substrate, which is considered a bad thing. But we found that this was a metastable phenomenon, meaning that we could deposit a thick enough layer to crack the substrate, but thin enough so that it didn't crack on its own -- it just needed a crack to get started." Their next discovery was how to make the crack initiation consistent and reliable. While there are many ways to generate a crack -- laser, chemical etching, thermal, mechanical, etc. -- it turns out that the simplest way, according to Bedell, is to terminate the thickness of the nickel layer very abruptly near the edge of the substrate. "This creates a large stress discontinuity at the edge of the nickel film so that once the tape is applied, a small pull on the tape consistently initiates the crack in that region," he said. Though it may not be obvious, gallium nitride is a vital material to our everyday lives. It's the underlying material used to fabricate blue, and now white, LEDs (for which the 2014 Nobel Prize in physics was awarded) as well as for high-power, high-voltage electronics. It may also prove useful for inherent biocompatibility, which when combined with control spalling may permit ultrathin bioelectronics or implantable sensors. "Controlled spalling has already been used to create extremely lightweight, high-efficiency GaAs-based solar cells for aerospace applications and flexible state-of-the-art circuits," Bedell said. The group is now working with research partners to fabricate high-voltage GaN devices using this approach. "We've also had great interaction with many of the GaN technology leaders through the Department of Energy's ARPA-E SWITCHES program and hope to use controlled spalling to enable novel devices through future partnerships," Bedell said. About American Institute of Physics The Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See http://jap.aip.org . 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 | May 26, 2017
One of the smallest historically black colleges in the U.S. boasts a huge accomplishment: pound for pound, tiny Dillard University in New Orleans graduates more physics majors -- and, notably, more female physics majors -- than far bigger schools with more resources. With an enrollment of 1,200, Dillard ranks second in the country in black physics undergrads. The point was punctuated at Dillard's recent commencement exercises, which featured a keynote address from actress and singer Janelle Monae, one of the stars of "Hidden Figures." The award-winning film tells the story of the black women scientists who fought Jim Crow while doing essential mathematical calculations for America's space program. "To see that we have this significant number of women representing (science and math) in the way that they are is a blessing to America and our future," Monae told The Associated Press in an interview before the May 13 graduation. "To have physicists coming out of New Orleans who are African-American women ... that's a huge deal." Nine of the top 10 physics departments in the country — at black or white schools — producing the most African American undergraduates in physics are at HBCUs, according to the American Institute of Physics. Currently, the top producing school is Morehouse College, an all-male HBCU with nearly twice as many students as Dillard. Dillard, the smallest on the list, ranked comparably with North Carolina A&T University, with more than 10,000 students. The private, liberal arts college has conferred 33 physics degrees since 2007, including nine to black women. Degrees in physics are rare for women and minorities. That Dillard — with a campus that is 73 percent female — is outpacing its larger counterparts is significant, said University of Pennsylvania higher education professor Marybeth Gasman. "They're taking a chance on these young women," said Gasman, director of Penn's Center for Minority-Serving Institutions and author of a forthcoming book on HBCUs and STEM -- science, technology, engineering and mathematics -- education. "They don't bring in people who they deem to be perfect. They bring people in who they deem to have potential and they work with them to discover this talent." Dillard President Walter Kimbrough is one of the biggest champions of the school's physics program. "I'd never met a black female getting an undergraduate degree in physics in my life until I got to Dillard," Kimbrough said. "It broadens the narrative of what black women do." Dillard's powerhouse program is the work of physics professor Abdalla Darwish, who frames his efforts to steer black women into the major as "a movement." "I believe in women, especially minority women," said Darwish, who arrived in 1998 and has built a multi-million dollar laser lab for research. "They are not less than anybody else. Just give them the chance and they will be the best. Give them what they need, and they will do." Founded in 1869, Dillard is best known for its nursing program, the oldest in the state. Physics was established as a major at Dillard in 1940. "You had those areas where we've traditionally expected women: teachers and nurses," Kimbrough said. "Now, we're going to be known as one of the best in physics. When I go out and talk about Dillard, it's a 'wow' factor for us." Trivia Frazier loved math from a young age, but in high school, she gravitated to science out of a curiosity for why things happen. "When I saw you could put an equation to something to describe it in a quantitative way, that's what really drew me to this field," Frazier said. She was the only person in her graduating high school class to pursue physics in college. She chose Dillard because of its eager, approachable recruiters — including Darwish, who talked to her about post-graduate studies. She went from being the only black girl in her school interested in physics, to having three "sisters in physics" at Dillard. "We were able to support each other and understand the quirks about being a physicist and not having the most popular major," Frazier said. "That was one of the most important components of my foundation." As an undergraduate, Frazier wondered what she would do with a physics degree, and considered adding mathematics to her major. Darwish was firm: A black woman in physics was special, he said.
News Article | June 8, 2017
Home > Press > New diode features optically controlled capacitance: Israeli researchers have developed a new optically tunable capacitor with embedded metal nanoparticles, creating a metal-insulator-semiconductor diode that is tunable by illumination. Abstract: A team of researchers at the Israel Institute of Technology has developed a new capacitor with a metal-insulator-semiconductor (MIS) diode structure that is tunable by illumination. The capacitor, which features embedded metal nanoparticles, is similar to a metal-insulator-metal (MIM) diode, except that the capacitance of the new device depends on illumination and exhibits a strong frequency dispersion, allowing for a high degree of tunability. This new capacitor has the potential to enhance wireless capability for information processing, sensing and telecommunications. The researchers report their findings this week in the Journal of Applied Physics, from AIP Publishing. "We have developed a capacitor with the unique ability to tune the capacitance by large amounts using light. Such changes are not possible in any other device," said Gadi Eisenstein, professor and director of the Russell Berrie Nanotechnology Institute at the Technion Israel Institute of Technology in Haifa and a co-author of the paper. "The observed photo sensitivity of this MIS diode structure expands its potential in optoelectronic circuits that can be used as a light-sensitive variable capacitor in remote sensing circuits." MIM diodes are common elements in electronic devices, especially those utilizing radio frequency circuits. They comprise thin-film metal plate electrodes that are separated by an insulator. Like the MIM structure, the researchers' new MIS capacitor is bias independent, meaning the constant capacitance is independent of its supply voltage. Bias-independent capacitors are important for high linearity, and therefore straightforward predictability, of circuit performance. "We have demonstrated that our MIS structure is superior to a standard MIM diode," said Vissarion (Beso) Mikhelashvili, senior research fellow at the Israel Institute of Technology and also a co-author of the paper. "On one hand, it has all the features of an MIM device, but the voltage independent capacitance is tunable by light, which means that the tuning functionality can be incorporated in photonic circuits." "The illumination causes a twofold effect," Eisenstein said. "First, the excitation of trap states enhances the internal polarization. Second, it increases the minority carrier density (due to photo generation) and reduces the depletion region width. This change modifies the capacitance." The researchers created three MIS structures, fabricated on a bulk silicon substrate, based on a multilayer dielectric stack, which consisted of a thin thermal silicon dioxide film and a hafnium oxide layer. The two layers were separated by strontium fluoride (SrF2) sublayers in which ferrum (Fe, iron) or cobalt (Co) nanoparticles were embedded. The researchers found that the fluoridation-oxidation process of the iron atoms causes the formation of a gradient in the valence state of iron ions across the active layer, which results in the generation of an electronic polarization. The polarization causes a bias-independent depletion region and hence an MIM-type characteristic. Four additional structures were prepared for comparison: Two lacked the SrF2 sublayers and one of them was prepared without the iron film. The other two structures contained SrF2: One did not have cobalt and the second included a one-nanometer Co layer. The comparison with other MIS capacitors that contained the metal nanoparticles with or without the SrF2 sublayers led to the unequivocal conclusion that only devices consisting of the combination of Fe and SrF2 turn the MIS structure into a photo-sensitive MIM-like structure. About American Institute of Physics Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See http://jap.aip.org . 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 | September 25, 2017
Home > Press > Enhancing the sensing capabilities of diamonds with quantum properties: A simple method can give diamonds the special properties needed for quantum applications such as sensing magnetic fields Abstract: Pure diamond consists of carbon atoms in a perfect crystal lattice. But remove a few carbons and swap some others for nitrogen, and you get a diamond with special quantum-sensing properties. These properties are useful for quantum information applications and sensing magnetic fields, and as a platform for probing the mysteries of quantum physics. When a nitrogen atom is next to the space vacated by a carbon atom, it forms what is called a nitrogen-vacancy (NV) center. Now, researchers have shown how they can create more NV centers, which makes sensing magnetic fields easier, using a relatively simple method that can be done in many labs. They describe their results this week in Applied Physics Letters, from AIP Publishing. Magnetic field sensing presents a prime example for the importance of this sensing. Green light can induce the NV centers to fluoresce and emit red light, but the amount of this fluorescence changes in the presence of a magnetic field. By measuring the brightness of the fluorescence, diamond NV centers can help determine magnetic field strength. Such a device can make magnetic images of a range of sample types, including rocks and biological tissue. The sensitivity of this type of magnetic detection is determined by the concentration of NV centers while vacancies that are not paired with nitrogen create noise. Efficient conversion of vacancies into NV centers, therefore, as well as maximizing the concentration of NV centers, plays a key role in advancing these detection methods. Researchers typically purchase nitrogen-doped diamonds from a separate company. They then bombard the diamond with electrons, protons or other particles, which strip away some of the carbon atoms, leaving behind vacancies. Finally, a heating process called annealing nudges the vacancies next to the nitrogen atoms to form the NV centers. The problem is that irradiation often requires sending your sample to a separate facility, which is expensive and time-consuming. "What is special about our approach is that it's very simple and very straightforward," said Dima Farfurnik of the Hebrew University of Jerusalem in Israel. "You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house." Their method uses high energy electron bombardment in a transmission electron microscope (TEM), an instrument accessible to many researchers, to locally create NV centers. Normally, a TEM is used to image materials down to subnanometer resolutions, but its narrow electron beam can also irradiate diamonds. Others have shown TEMs can create NV centers in specialized diamond samples, but the researchers in this study successfully tested the method on several commercially available diamond samples. In a typical, untreated sample, less than 1 percent of the nitrogen atoms form NV centers. But by using a TEM, the researchers increased this conversion efficiency to as high as 10 percent. In certain cases, the samples reached their saturation limit, and more irradiation was no longer effective. For other samples, however, the researchers didn't hit this limit, suggesting that additional irradiation could boost efficiencies further. With higher conversion efficiencies, and small irradiation volumes possible with a TEM, devices like magnetic sensors could be more compact. To make sure the method didn't hinder the effectiveness of NVs in applications like sensing magnetic fields, the researchers confirmed that the length of time the NV centers remain in their states -- the coherence time -- didn't change. Packing enough NV centers in a diamond would allow physicists to probe the quantum interactions among the centers themselves. This research could enable the creation of a unique quantum state called a squeezed state, which has never been demonstrated before in a solid and could push the sensing capabilities of these systems beyond today's classical limits. "We hope the enhanced number of NV centers due to irradiation will serve as a stepping stone for this long-term and ambitious goal," Farfurnik said. About American Institute of Physics Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See http://apl.aip.org . 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.
Agency: NSF | Branch: Standard Grant | Program: | Phase: SPECIAL PROGRAMS IN ASTRONOMY | Award Amount: 149.41K | Year: 2013
Past snapshots of the fraction of professional astronomers who are women at various career stages have suggested a higher attrition rate than for men. While anecdotal evidence suggests possible reasons, reliable statistical data and analyses are lacking. This award will enable the PI to follow a cohort of men and women astronomers over a decade, track the decisions they make, and make links to underlying causes. The time period is key to success, collecting data from the cohort in three staged surveys. The award will support the analysis of data from the second survey round, the preparation of the third survey and its analysis, and linking together the ultimate findings and conclusions from the complete program. Using data from all three rounds, the Longitudinal Study will ultimately: (1) provide detailed data on trends in employment over 10+ years for a single cohort, (2) collect data on people who leave the field of astronomy during or after graduate school, (3) determine whether there are sex differences in attrition from astronomy and reasons for this, and (4) examine factors that precede decisions to persist in, or leave, the field of astronomy.