The Homeland Defense and Security Information Analysis Center (HDIAC) is a Department of Defense (DoD) sponsored organization through the Defense Technical Information Center (DTIC)
• HDIAC utilizes expertise and knowledge from government agencies, research institutions, laboratories, industry and academia on topics relevant to the DoD and other government entities to solve the government’s toughest scientific and technical problems
• Develop two State-of-the-Art Reports each year on a pressing topic related to the Defense community within HDIAC focus areas
• Manipulation of matter on a scale of 1 to 100 nanometers (nm) in at least one dimension to create new structures and materials
• The modification of surfaces is fundamental to engineering and technological innovation, because almost everything about a product or device can be affected by its surface functionality and interaction with the environment.
The schematic at left shows the design for an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft. At …more
Researchers have demonstrated the high-performance potential of an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft.
The semiconductor is promising for next-generation “power electronics,” or devices needed to control the flow of electrical energy in circuits. Such a technology could help to reduce global energy use and greenhouse gas emissions by replacing less efficient and bulky power electronics switches now in use.
The transistor, called a gallium oxide on insulator field effect transistor, or GOOI, is especially promising because it possesses an “ultra-wide bandgap,” a trait needed for switches in high-voltage applications.
Compared to other semiconductors thought to be promising for the transistors, devices made from beta gallium oxide have a higher “breakdown voltage,” or the voltage at which the device fails, said Peide Ye, Purdue University’s Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering.
Findings are detailed in a research paper published this month in IEEE Electron Device Letters. Graduate student Hong Zhou performed much of the research.
The team also developed a new low-cost method using adhesive tape to peel off layers of the semiconductor from a single crystal, representing a far less expensive alternative to a laboratory technique called epitaxy. The market price for a 1-centimeter-by-1.5-centimeter piece of beta gallium oxide produced using epitaxy is about $6,000. In comparison, the “Scotch-tape” approach costs pennies and it can be used to cut films of the beta gallium oxide material into belts or “nano-membranes,” which can then be transferred to a conventional silicon disc and manufactured into devices, Ye said.
The technique was found to yield extremely smooth films, having a surface roughness of 0.3 nanometers, which is another factor that bodes well for its use in electronic devices, said Ye, who is affiliated with the NEPTUNE Center for Power and Energy Research, funded by the U.S. Office of Naval Research and based at Purdue’s Discovery Park. Related research was supported by the center.
The Purdue team achieved electrical currents 10 to 100 times greater than other research groups working with the semiconductor, Ye said.
One drawback to the material is that it possesses poor thermal properties. To help solve the problem, future research may include work to attach the material to a substrate of diamond or aluminum nitride.
This technology would enable communities to produce their own water filters using biomass nanofibers, making clean water more accessible and affordable – Follow the Link below to Watch the Video.
The world’s population is projected to increase by 2-3 billion over the next 40 years. Already, more than three quarters of a billion people lack access to clean drinking water and 85 percent live in the driest areas of the planet.
Those statistics are inspiring chemist Ben Hsiao and his team at Stony Brook University. With support from the National Science Foundation (NSF), the team is hard at work designing nanometer-scale water filters that could soon make clean drinking water available and affordable for even the poorest of the poor.
Traditional water filters are made of polymer membranes with tiny pores to filter out bacteria and viruses. Hsiao’s filters are made of fibers that are all tangled up, and the pores are the natural gaps between the strands. The team’s first success at making the new nanofilters uses a technique called electrospinning to produce nanofibers under an electrical field.
Hsiao’s team is also looking to cut costs even further by using “biomass” nanofibers extracted from trees, grasses, shrubs — even old paper. Hsiao says it will be a few years yet before the environmentally friendly biomass filters are ready for widespread use in developing countries, but the filters will eliminate the need to build polymer plants in developing areas. Ultimately, those filters could be produced locally with native biomass or biowaste.
The research in this episode was supported by NSF award #1019370, Breakthrough Concepts on Nanofibrous Membranes with Directed Water Channels for Energy-Saving Water Purification.
An international team of researchers led by Russian scientists has developed a new method of using silicon nanoparticles instead of expensive semiconductor materials for certain types of displays and other optoelectronic devices.
Lomonosov MSU physicists found a way to “force” silicon nanoparticles to glow in response to radiation strongly enough to replace expensive semiconductors used in the display business. According to Maxim Shcherbakov, researcher at the Department of Quantum Electronics of Moscow State University and one of the authors of the study, the method considerably enhances the efficiency of nanoparticle photoluminescence.
The key to the technique is photoluminescence—the process by which materials irradiated by visible or ultraviolet radiation respond with their own light, but in a different spectral range. In the study, the material glows red.
In some modern displays, semiconductor nanoparticles, or so-called quantum dots, are used. In quantum dots, electrons behave completely unlike those in the bulk semiconductor, and it has long been known that quantum dots possess excellent luminescent properties. Today, for the purposes of quantum-dot based displays, expensive and toxic materials are used; therefore, researchers have explored the use of silicon, which is cheaper and well understood. It is suitable for such use in all respects except one—silicon nanoparticles weakly respond to radiation, which is not appealing for optoelectronic industry.
Scientists all over the world have sought to solve this problem since the beginning of the 1990s, but until now, no significant success has been achieved. The breakthrough idea about how to “tame” silicon originated in Sweden, at the Royal Institute of Technology, Kista. A post-doctoral researcher named Sergey Dyakov, a graduate of the MSU Faculty of Physics and the first author of the paper, suggested placing an array of silicon nanoparticles in a matrix with a non-homogeneous dielectric medium and covering it with golden nanostripes.
“The heterogeneity of the environment, as has been previously shown in other experiments, allows to increase the photoluminescence of silicon by several orders of magnitude due to the so-called quantum confinement,” says Maxim Shcherbakov.
“However, the efficiency of the light interaction with nanocrystals still remains insufficient. It has been proposed to enhance the efficiency by using plasmons (quasiparticle appearing from fluctuations of the electron gas in metals—ed). A plasmon lattice formed by gold nanostripes ‘held’ light on the nanoscale, and allowed a more effective interaction with nanoparticles located nearby, bringing its luminescence to an increase.”
The MSU experiments with samples of a “gold-plated” matrix with silicon nanoparticles brilliantly confirmed the theoretical predictions—the UV irradiated silicon shone brightly enough to be used it in practice.
Top: High-resolution electron microscopy images of a nickel silicide rhombic nanocrystal embedded in a silicon nanowire prepared with gold silicide used as a catalyst. The images demonstrate the intimate interactions that arise at the interfaces of these nanomaterials. Bottom: The physical properties that arise from such complex nano-systems could be used in next-generation photodetectors, lasers, and transistors.
Credit: Image courtesy of Department of Energy, Office of Science
As any good carpenter knows, it’s often easier to get what you want if you build it yourself. An international team using resources at the Center for Functional Nanomaterials took that idea to heart. They wanted to tailor extremely small wires that carry light and electrons. They devised an approach that lets them tailor the wires through exquisite control over the structures at the nanoscale. New structures could open up a potential path to a wide range of smaller, lighter, or more efficient devices.
This development could lead to highly tailored nanowires for new classes of high-performance, energy-efficient computing, communications, and environmental and medical sensing systems. The resulting devices could lead to smaller electronics as well as improving solar panels, photodetectors, and semiconductor lasers.
Semiconducting nanowires have a wide range of existing and potential applications in optoelectronic materials, from single-electron transistors and tunnel diodes, to light-emitting semiconducting nanowires to energy-harvesting devices. An international collaboration led by the University of Cambridge and IBM has demonstrated a new method to create novel nanowires that contain nanocrystals embedded within them. They accomplished this by modifying the classic “vapor-liquid-solid” crystal growth method, wherein a liquid-phase catalyst decomposes an incoming gas-phase source and mediates the deposition of the solid, growing nanowire.
In this work, a bimetallic catalyst is used. The team showed that by appropriate thermal treatment, it is possible to crystallize a solid silicide structure within the liquid catalyst, and then attach the nanowire to the solid silicon in a controlled epitaxial fashion. The Center for Functional Nanomaterials’ Electron Microscopy Facility was employed to image the nanomaterials by high spatial-resolution, aberration-corrected transmission electron microscopy. As well, scientists used a first-of-its-kind direct electron detector to obtain high temporal-resolution images of the fabrication process. Incorporating these instruments with the expertise and insight of the scientific team led to fantastic, nanoscale control over these structures and presents notable potential for a broad range of potential devices, like photodetectors and single electron transistors.
F. Panciera, Y.-C. Chou, M. C. Reuter, D. Zakharov, E. A. Stach, S. Hofmann, F. M. Ross. Synthesis of nanostructures in nanowires using sequential catalyst reactions. Nature Materials, 2015; 14 (8): 820 DOI:10.1038/nmat4352
To continue advancing, next-generation electronic devices must fully exploit the nanoscale, where materials span just billionths of a meter. But balancing complexity, precision, and manufacturing scalability on such fantastically small scales is inevitably difficult. Fortunately, some nanomaterials can be coaxed into snapping themselves into desired formations-a process called self-assembly.
Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have just developed a way to direct the self-assembly of multiple molecular patterns within a single material, producing new nanoscale architectures. The results were published in the journal Nature Communications.
“This is a significant conceptual leap in self-assembly,” said Brookhaven Lab physicist Aaron Stein, lead author on the study. “In the past, we were limited to a single emergent pattern, but this technique breaks that barrier with relative ease. This is significant for basic research, certainly, but it could also change the way we design and manufacture electronics.”
Microchips, for example, use meticulously patterned templates to produce the nanoscale structures that process and store information. Through self-assembly, however, these structures can spontaneously form without that exhaustive preliminary patterning. And now, self-assembly can generate multiple distinct patterns-greatly increasing the complexity of nanostructures that can be formed in a single step.
“This technique fits quite easily into existing microchip fabrication workflows,” said study coauthor Kevin Yager, also a Brookhaven physicist. “It’s exciting to make a fundamental discovery that could one day find its way into our computers.”
The experimental work was conducted entirely at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, leveraging in-house expertise and instrumentation.
Cooking up organized complexity
The collaboration used block copolymers-chains of two distinct molecules linked together-because of their intrinsic ability to self-assemble.
“As powerful as self-assembly is, we suspected that guiding the process would enhance it to create truly ‘responsive’ self-assembly,” said study coauthor Greg Doerk of Brookhaven. “That’s exactly where we pushed it.”
To guide self-assembly, scientists create precise but simple substrate templates. Using a method called electron beam lithography-Stein’s specialty-they etch patterns thousands of times thinner than a human hair on the template surface. They then add a solution containing a set of block copolymers onto the template, spin the substrate to create a thin coating, and “bake” it all in an oven to kick the molecules into formation. Thermal energy drives interaction between the block copolymers and the template, setting the final configuration-in this instance, parallel lines or dots in a grid.
“In conventional self-assembly, the final nanostructures follow the template’s guiding lines, but are of a single pattern type,” Stein said. “But that all just changed.”
Lines and dots, living together
The collaboration had previously discovered that mixing together different block copolymers allowed multiple, co-existing line and dot nanostructures to form.
“We had discovered an exciting phenomenon, but couldn’t select which morphology would emerge,” Yager said. But then the team found that tweaking the substrate changed the structures that emerged. By simply adjusting the spacing and thickness of the lithographic line patterns-easy to fabricate using modern tools-the self-assembling blocks can be locally converted into ultra-thin lines, or high-density arrays of nano-dots.
“We realized that combining our self-assembling materials with nanofabricated guides gave us that elusive control. And, of course, these new geometries are achieved on an incredibly small scale,” said Yager.
“In essence,” said Stein, “we’ve created ‘smart’ templates for nanomaterial self-assembly. How far we can push the technique remains to be seen, but it opens some very promising pathways.”
Gwen Wright, another CFN coauthor, added, “Many nano-fabrication labs should be able to do this tomorrow with their in-house tools-the trick was discovering it was even possible.”
The scientists plan to increase the sophistication of the process, using more complex materials in order to move toward more device-like architectures.
“The ongoing and open collaboration within the CFN made this possible,” said Charles Black, director of the CFN. “We had experts in self-assembly, electron beam lithography, and even electron microscopy to characterize the materials, all under one roof, all pushing the limits of nanoscience.”