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<?xml version="1.0" encoding="UTF-8"?> Photo: Dan Hixson/University of Utah College of Engineering Researchers at the University of Utah have developed the first stable intrinsic p-type (carrying positive charges) 2-D semiconductor material, tin oxide. If this semiconductor is mated with a n-type (carrying electrons) 2-D semiconductor in a transistor, it opens up the possibility of building power-saving two-dimensional complementary logic circuits like the ones in microprocessors today. "Now we have everything—we have p-type 2-D semiconductors and n-type 2-D semiconductors," said Ashutosh Tiwari, an associate professor at the University of Utah and the leader of the research, in a press release. "Now things will move forward much more quickly." The potential for 2-D materials—such as graphene and molybdenum disulfide—as an alternative to the three-dimensional silicon, raises hopes for smaller, faster, lower-power transistors. However, the path to success for these 2-D materials in transistors has not always been clear, whether it be issues such as graphene not being a natural semiconductor or the charge carrier traps that compromise molybdenum disulfide. But possibly the biggest issue has been that all previous 2-D materials have only been stable n-type semiconductors. It has been possible to dope other 2-D materials, such as molybdenum disulfide and tungsten diselenide, to behave as p-type. However, this new tin oxide represents the first intrinsic p-type semiconductor in a 2D material. In research described in the journal Advanced Electronic Materials , the Utah University researchers overcame this limitation by layering 2-D tin oxide (SnO) onto a sapphire-and-silicon-dioxide (SiO2) substrate. The researchers were then able to fabricate a few field-effect transistors (FETs) from it. With this development, the attractive properties of 2-D materials in transistors are more fully exploitable. For instance, in 2-D materials charge transport is basically confined to a single plane, meaning electrical and thermal transport properties that can be much better than those of bulk silicon. That could mean chips that consume less power and throw-off less heat. In an e-mail interview, Tiwari said that the next step in their research will be to build a CMOS (complementary metal oxide semiconductor) using their new p-type 2-D semiconductor. This post was corrected on 18 February to indicate that some 2-D materials could act as p-type semiconductors when doped.
Printed Electronics WorldGraphene leans on glass to advance electronicsPrinted Electronics World"Developing and characterizing the devices required complex nanofabrication, delicate transfer of the atomically thin graphene onto rough substrates, detailed structural and electro-optical characterization, and also the ability to grow the CIGS ...and more »
The University of California, Riversides Bourns College of Engineering recently announced its partnership with Pearson to create a new online degree program in engineering, with specializations in bi...
Haydale, a leader in the development of enhanced graphene and nanoparticulate materials, has announced that it has been awarded a number of research grants, totalling £350k, which will help accelerate...
Graphene combines transparency, electrical conductivity, and high durability into a one-atom-thick sheet of carbon. Even though graphene is known to be a "wonder material," it has still not...
Engineering material magic: Utah engineers discover groundbreaking semiconducting material that could lead to much faster electronics
University of Utah engineers have discovered a new kind of 2D semiconducting material for electronics that opens the door for much speedier computers and smartphones that also consume a lot less power...
We speak to Jae Hyun Lee, winner of the first Nanotechnology Young Researcher Award about the challenges and motivations in his nanobioscience work.
SUNY Poly and GLOBALFOUNDRIES Announce New $500M R&D Program in Albany To Accelerate Next Generation Chip Technology: Arrival of Second Cutting Edge EUV Lithography Tool Launches New Patterning Center That Will Generate Over 100 New High Tech Jobs at SUNY
In support of Governor Andrew M. Cuomos commitment to maintaining New York States global leadership in nanotechnology research and development, SUNY Polytechnic Institute (SUNY Poly) and GLOBALFOUND...
New thin film transistor may lead to flexible devices: Researchers engineer an electronics first, opening door to flexible electronics
An engineering research team at the University of Alberta has invented a new transistor that could revolutionize thin-film electronic devices.
Today, computer chips are built by stacking layers of different materials and etching patterns into them. But in the latest issue of Advanced Materials, MIT researchers and their colleagues report the first chip-fabrication technique that enables significantly different materials to be deposited in the same layer. They also report that, using the technique, they have built chips with working versions of all the circuit components necessary to produce a general-purpose computer. The layers of material in the researchers’ experimental chip are extremely thin — between one and three atoms thick. Consequently, this work could abet efforts to manufacture thin, flexible, transparent computing devices, which could be laminated onto other materials. “The methodology is universal for many kinds of structures,” says Xi Ling, a postdoc in the Research Laboratory of Electronics and one of the paper’s first authors. “This offers us tremendous potential with numerous candidate materials for ultrathin circuit design.” The technique also has implications for the development of the ultralow-power, high-speed computing devices known as tunneling transistors and, potentially, for the integration of optical components into computer chips. “It’s a brand new structure, so we should expect some new physics there,” says Yuxuan Lin, a graduate student in electrical engineering and computer science and the paper’s other first author. Ling and Lin are joined on the paper by Mildred Dresselhaus, an Institute Professor emerita of physics and electrical engineering; Jing Kong, an ITT Career Development Professor of Electrical Engineering; Tomás Palacios, an associate professor of electrical engineering; and by another 10 MIT researchers and two more from Brookhaven National Laboratory and Taiwan’s National Tsing-Hua University. Strange bedfellows Computer chips are built from crystalline solids, materials whose atoms are arranged in a regular geometrical pattern known as a crystal lattice. Previously, only materials with closely matched lattices have been deposited laterally in the same layer of a chip. The researchers’ experimental chip, however, uses two materials with very different lattice sizes: molybdenum disulfide and graphene, which is a single-atom-thick layer of carbon. Moreover, the researchers’ fabrication technique generalizes to any material that, like molybdenum disulfide, combines elements from group six of the periodic table, such as chromium, molybdenum, and tungsten, and elements from group 16, such as sulfur, selenium, and tellurium. Many of these compounds are semiconductors — the type of material that underlies transistor design — and exhibit useful behavior in extremely thin layers. Graphene, which the researchers chose as their second material, has many remarkable properties. It’s the strongest known material, but it also has the highest known electron mobility, a measure of how rapidly electrons move through it. As such, it’s an excellent candidate for use in thin-film electronics or, indeed, in any nanoscale electronic devices. To assemble their laterally integrated circuits, the researchers first deposit a layer of graphene on a silicon substrate. Then they etch it away in the regions where they wish to deposit the molybdenum disulfide. Next, at one end of the substrate, they place a solid bar of a material known as PTAS. They heat the PTAS and flow a gas across it and across the substrate. The gas carries PTAS molecules with it, and they stick to the exposed silicon but not to the graphene. Wherever the PTAS molecules stick, they catalyze a reaction with another gas that causes a layer of molybdenum disulfide to form. In previous work, the researchers characterized a range of materials that promote the formation of crystals of other compounds, any of which could be plugged into the process. Future electronics The new fabrication method could open the door to more powerful computing if it can be used to produce tunneling-transistor processors. Fundamentally, a transistor is a device that can be modulated to either allow a charge to cross a barrier or prohibit it from crossing. In a tunneling transistor, the charge crosses the barrier by means of a counterintuitive quantum-mechanical effect, in which an electron can be thought of as disappearing at one location and reappearing at another. These effects are subtle, so they’re more pronounced at extremely small scales, like the one- to three-atom thicknesses of the layers in the researchers’ experimental chip. And, because electron tunneling is immune to the thermal phenomena that limit the efficiency of conventional transistors, tunneling transistors can operate at very low power and could achieve much higher speeds. "This work is very exciting,” says Philip Kim, a physics professor at Harvard University. “The MIT team demonstrated that controlled stitching of two completely different, atomically thin 2-D materials is possible. The electrical properties of the resulting lateral heterostructures are very impressive."
In November 2014, the Sustainable Nanotechnology Organization (SNO), a non-profit, international, professional society, held its 3rd annual conference in Boston with over 220 participants in attendance. Drs. Jackie Isaacs of Northeastern University and Philp Demokritou of Harvard University co-chaired the meeting. SNO is dedicated to advancing sustainable nanotechnology around the world through education, research, and responsible growth of nanotechnology. This themed collection is the summary of representative research papers presented at the Boston conference. Seven eminent scientists and engineers in the field of sustainable nanotechnology gave plenary lectures attended by participants from almost every U.S. state as well as many other countries. About 45% of participants were students, indicative of the recentness of the field. Selected papers from the conference highlight how sustainable nanotechnology is leading the way to address economic development, global food supplies, as well as energy and water challenges while leaving minimal footprints that can give rise to environmental degradation. Some of the papers represent the core aspects of sustainable nanotechnology, including biomedical applications, water treatment, green synthesis, life cycle assessments (LCA) and NanoEHS issues. Demokritou et al. present an integrated methodology for the assessment of environmental health implications during thermal decomposition of nano-enabled products. Demokritou et al., DOI: 10.1039/C4EN00210E An article by Vicki Grassian et al. reports an important finding that simple nanoscale materials can be complex when considering NanoEHS implications. A number of the fundamental research areas to address NanoEHS needs are suggested. Grassian et al., DOI: 10.1039/C5EN00112A In a review article by Gilbertson, Wender, Zimmerman, and co-workers, the authors summarize recent advances in human and aquatic ecotoxicity life cycle impact assessment for engineered nanomaterials (ENMs) and call for greater coordination between LCA modelers and experimentalists, including those who study fate and transport, environmental transformations, occupational exposure, and toxicology, to inform responsible development of nanotechnology, enabling the technology to reach its full potential. Gilbertson et al., DOI: 10.1039/C5EN00097A The development of nanomaterials and nano-enabled products in a “greener” manner will minimize any EHS implications while maximizing the societal benefits. Companies working with engineered nanomaterials are expected to make tradeoffs on the costs associated with increased levels of occupational safety and potential environmental impacts. For example, Isaacs et al. present a paper on the economic analysis of carbon nanotube (CNT) lithium-ion battery manufacturing. These authors present a stochastic process-based cost model to investigate the cost drivers for the manufacture of multi-walled CNT nickel manganese cobalt batteries that are targeted for satellite and computer applications. Among other things their results underscore the need for safer manufacturing practices for CNT lithium-ion batteries for application in low and high production volume products such as satellites and portable computers, respectively. Isaacs et al., DOI: 10.1039/C5EN00078E Greener nanotechnology can be the “role model” for industrial development in the 21st century. Sadik et al. demonstrate that a one-pot synthesis of silver and gold nanoparticles is possible using conductive, electroactive, and biodegradable polymers. In addition to modest cytotoxicity against non-cancerous, immortalized and cancerous cell lines, the synthesized nanoparticles exhibit excellent antibacterial activity against gram negative and gram positive bacteria. Sadik et al., DOI: 10.1039/C5EN00053J Pourzahedi et al. apply green chemistry and sustainable manufacturing to nanomaterial synthesis, with the goal of reducing life cycle energy use and environmental impacts. The authors use LCA to analyze and compare the environmental impacts of AgNPs produced through seven different synthesis routes (cradle-to-gate). LCA reveals both direct and indirect or upstream impacts associated with AgNPs. Results show that across synthesis routes, impacts associated with the upstream production of bulk silver itself are dominant for nearly every category of environmental impact, contributing to over 90% of life cycle burdens in some cases. The bio-based chemical reduction route has important tradeoffs in ozone depletion potential and ecotoxicity. Pourzahedi et al., DOI: 10.1039/C5EN00075K The release of ENMs into the environment has led to concerns about the potential risks to food safety and human health. Ebbs et al. describe the extent of ENM uptake into plant foods. The authors focus on the accumulation of zinc, copper, or cerium in carrot exposed to metal oxide nanoparticles and metal ions. They demonstrate that ENMs are no more toxic than the ionic treatments and show a reduced accumulation in the edible tissues of carrot. The results demonstrate that the understanding of ionic metal transport in plants may not accurately predict ENM transport and that an additional comparative study is needed for this and other crop plants. Ebbs et al., DOI: 10.1039/C5EN00161G Rodrigues et al. provide an assessment of the toxicity of exfoliated-MoS2 and annealed exfoliated-MoS2 towards planktonic cells, biofilms, and mammalian cells in the presence of electron donor. Rodrigues et al., DOI: 10.1039/C5EN00031A Lee et al. report the development of precisely engineered manganese oxide nanoscale particles for the sorption of uranium as uranyl in water. They synthesize nanoparticles via thermal decomposition of manganese oleate and then phase-transfer the particles into water using ligand exchange and bilayer stabilization methods. The resulting monodisperse suspensions demonstrate significantly enhanced uranyl adsorption as a function of size, surface coating chemistries, and solution pH. Lee et al., DOI: 10.1039/C5EN00010F The fate of dysprosium oxide nanoparticles (Dy2O3) and their effects on natural biological systems are a growing concern. Oyanedel-Craver et al. have assessed the toxicity of nDy2O3 on Escherichia coli for concentrations between 0.02 and 2 mg/L exposed to three concentrations of NaCl and three glucose concentrations. Toxicity measurement of Dysprosium ion Dy(+3) suggest that it is the main contributor to the overall toxicity. Oyanedel-Craver et al., DOI: 10.1039/C5EN00074B Among other applications, engineered superparamagnetic nanoparticles have broad potential in biotechnologies, high contrast magnetic resonance imaging, and advanced environmental sensing and remediation technologies. Fortner et al. present the flexible surface design strategies for a variety of superparamagnetic iron oxide nanoparticles for applications in aqueous systems. Fortner et al., DOI: 10.1039/C5EN00089K Chen et al. describe the aggregation and interactions of chemical mechanical planarization nanoparticles with model biological membranes, focusing on the role of phosphate adsorption. Chen et al., DOI: 10.1039/C5EN00176E The difficulty of meeting the world’s energy demand is compounded by the growing need to protect human health and the environment. Nanotechnology will play a major role in the development of clean, affordable, and renewable energy sources. Soroush et al. demonstrate that silver nanoparticle (AgNPs)-decorated graphene oxide (GO) functionalized membranes exhibit super-hydrophilic properties with contact angles below 25°. The membranes also exhibit significant E. coli inactivation without adversely affecting the membrane transport properties. Such membrane could be employed as composites of forward osmosis and seawater desalination because of its energy efficiency. Soroush et al., DOI: 10.1039/C5EN00086F We hope you enjoy this issue which represents a snapshot of the wider conversation on the topic of sustainable nanotechnology. We also invite you to visit us at www.susnano.org as we develop a framework for using nanotechnology to address grand global challenges in the energy, water, and food sectors while maintaining a balance between the economic, environmental, and societal issues. Enjoy this issue! Wunmi Sadik, President & Co-founder Barbara Karn, Executive Director & Co-founder Jacqueline Isaacs and Philip Demokritou, SNO 2014 Co-Chairs