Category Archives: Process Materials

A team of scientists from Siberian Federal University (SibFU) together with foreign colleagues described the structural and physical properties of a group of two-dimensional materials based on polycyclic molecules called circulenes. The possibility of flexible design and variable properties of these materials make them suitable for nanoelectronics. The results are published in the Journal of Physical Chemistry C.

Circulenes are organic molecules that consist of several hydrocarbon cycles forming a flower-like structure. Their high stability, symmetricity, and optical properties make them of special interest for nanoelectronics especially for solar cells and organic LEDs. The most stable and most studied tetraoxa[8]circulene molecule could be potentially polymerized into graphene-like nanoribbons and sheets. The authors have published the results of simulations proving this possibility. They also described properties and structure of the proposed materials.

“Having only one building block – a tetraoxa[8]circulene molecule – one can create a material with properties similar to those of silicon (a semiconductor traditionally used in electronics) or graphene (a semimetal) depending on the synthesis parameters. However, the proposed materials have some advantages. The charge carrier mobility is about 10 times higher compared to silicon, therefore, one could expect higher conductivity,” says the main author of the study Artem Kuklin, research associate at the department of theoretical physics of Siberian Federal University.

Having the equilibrium geometries and tested their stability, the scientists discovered several stable tetraoxa[8]circulene-based polymers. The difference between them lied in the type of coupling between the molecules resulting in different properties. The polymers demonstrate high charge carrier mobility. This property was analyzed by fitting of energy zones near bandgap – a parameter represented by separation of empty and occupied electronic states. The mechanical properties exhibit that the new materials 1.5-3 times more stretchable than graphene. The authors also emphasized existence of topological states in one of the polymers caused by spin-orbit coupling, which is not typical for light elements-based materials. The materials possessed such kind of properties are insulators in the bulk but can conduct electricity on the surface (edges).

“The proposed nanostructures possess useful properties and may be used in various fields, from the production of ionic sieves to elements of nanoelectronic devices. Further we plan to develop this topic and modify our compounds with metal adatoms to study their magnetic and catalytic properties. We would also like to find a research group that could synthesize these materials,” concludes Artem Kuklin.

Two-dimensional magnetism has long intrigued and motivated researchers for its potential to unleash new states of matter and utility in nano-devices.

In part the excitement is driven by predictions that the magnetic moments of electrons – known as “spins” – would no longer be able to align in perfectly clean systems. This enhancement in the strengths of the excitations could unleash numerous new states of mater, and enable novel forms of quantum computing.

A key challenge has been the successful fabrication of perfectly clean systems and their incorporation with other materials. However, for more than a decade, materials known as “van der Waals” crystals, held together by friction, have been used to isolate single-atom-thick layers leading to numerous new physical effects and applications.

Recently this class has been expanded to include magnetic materials, and it may offer one of the most ambitious platforms yet in scientific efforts to investigate and manipulate phases of matter at the nanoscale, researchers from Boston College, the University of Tennessee, and Seoul National University, write in the latest edition of the journal Nature.

Two-dimensional magnetism, the subject of theoretical explorations and experimentation for the past 80 years, is enjoying a resurgence thanks to a group of materials and compounds that are relatively plentiful and easy to manipulate, according to Boston College Associate Professor of Physics Kenneth Burch, a first author of the article “‘Magnetism in two-dimensional van der Waals materials.”

The most oft-cited example of these materials is graphene, a crystal constructed in uniform, atom-thick layers. A procedure as simple as applying a piece of scotch tape to the crystal can remove a single layer, providing a thin, uniform section to serve as a platform to create novel materials with a range of physical properties open to manipulation.

“What’s amazing about these 2-D materials is they’re so flexible,” said Burch. “Because they are so flexible, they give you this huge array of possibilities. You can make combinations you could not dream of before. You can just try them. You don’t have to spend this huge amount of time and money and machinery trying to grow them. A student working with tape puts them together. That adds up to this exciting opportunity people dreamed of for a long time, to be able to engineer these new phases of matter.”

At that single layer, researchers have focused on spin, what Burch refers to as the “magnetic moment” of an electron. While the charge of an electron can be used to send two signals – either “off” or “on”, results represented as either zero or one – spin excitations offer multiple points of control and measurement, an exponential expansion of the potential to signal, store or transmit information in the tiniest of spaces.

“One of the big efforts now is to try to switch the way we do computations,” said Burch. “Now we record whether the charge of the electron is there or it isn’t. Since every electron has a magnetic moment, you can potentially store information using the relative directions of those moments, which is more like a compass with multiple points. You don’t just get a one and a zero, you get all the values in between.”

Potential applications lie in the areas of new “quantum” computers, sensing technologies, semiconductors, or high-temperature superconductors.

“The point of our perspective is that there has been a huge emphasis on devices and trying to pursue these 2-D materials to make these new devices, which is extremely promising,” said Burch. “But what we point out is magnetic 2D atomic crystals can also realize the dream of engineering these new phases – superconducting, or magnetic or topological phases of matter, that is really the most exciting part. It is not just fundamentally interesting to realize these theorems that have been around for 40 years. These new phases would have applications in various forms of computing, whether in spintronics, producing high temperature superconductors, magnetic and optical sensors and in topological quantum computing.”

Burch and his colleagues – the University of Tennessee’s David Mandrus and Seoul National University’s Je-Geun Park – outline four major directions for research into magnetic van der Waals materials:

  • Discovering new materials with specific functionality. New materials with isotropic or complex magnetic interactions, could play significant roles in the development of new supercondcutors.
  • These new materials can also lead to a deeper understanding of fundamental issues in condensed matter physics, serving as unique platforms for experimentation.
  • The materials will be tested for the potential to become unique devices, capable of delivering novel applications. The two-dimensional structure of these materials makes them more receptive to external signals.
  • These materials possess quantum and topological phases that could potentially lead to exotic states, such as quantum spin liquids, “skyrmions,” or new iterations of superconductivity.

Germano Iannacchione, a National Science Foundation (NSF) program officer who oversees grants to Burch and other materials scientists, said the co-authors offer the broader community of scientists ideas that can serve to guide a dynamic field pushing beyond boundaries in materials research.

“Magnetism in 2D van Der Waals materials has grown into a vibrant field of study,” said Iannacchione. “Its investigators have matured from highly focused researchers to statesmen shepherding a field, broadening applications into as many channels as possible. The review captures the multiplicative aspect of steady, focused, and sometimes risky research that opens vast new frontiers, with tremendous potential for applications in quantum computing and spintronics.”

In a paper published in NANO, researchers from the School of Microelectronics in Tianjin University have discovered a two-step sputtering and subsequent annealing treatment method to prepare vertically aligned WO3-CuO core-shell nanorod arrays which can detect toxic NH3 gas.

A schematic illustration of the gas sensor device based on the hybrid nanorod arrays. The real time resistance versus time of the vertically aligned WO3-CuO core-shell nanorod arrays-based gas sensor to varied concentrations of NH3 decreasing from 500 ppm to 50 ppm at 150 ?. The resistance of the WO3-CuO hybrid increases upon exposure to NH3, consistent with p-type semiconductor behavior. The response of the hybrid sample increasing with increasing NH3 concentration at 150. The response and recovery times range from 10 to 15 s for all NH3 concentrations. Credit: Author

Over the years, WO3 has received considerable attention among the numerous transition metal oxides as a wide band-gap n-type semiconductor in various gas detection, such as NOx, H2S, H2, and NH3. CuO has the unique property of being intrinsically p-type. In the last decade, p-n heterojunction sensors composed of an n-type metal oxide and CuO were reported to have a good sensitivity to reducing gases owing to the interface between n-metal oxide and CuO. Much effort has been focused on the WO3-based nanocomposites, since the synergetic enhancement and heterojunction effects attributes to the enhanced gas sensing properties. However, gas sensors based on 1D WO3-CuO composite structures are limited. Additionally, the template or catalyst was usually necessary to synthesize WO3-based nanorod arrays, including using chemical vapor deposition, electrochemical anodization and hydrothermal approaches.

Among toxic gases causing adverse impact on living organisms, NH3 is one of the most hazardous substances. It is necessary to build up ultrasensitive NH3 gas sensors with short response and recovery time. Metal oxides have been widely used in gas sensor applications. In order to obtain great sensing performances of metal oxide sensors, 1D metal oxide nanostructures and 1D heterojunction composite nanostructures have been investigated due to their large surface area, size-dependent properties, and the nano-heterojunction effects. Vertically aligned ordered 1D arrays effectively avoid the dense stacking of rod monomers, especially, resulting in novel physicochemical characteristics, such as higher gas response and shorter gas recovery.

Here, vertically aligned WO3-CuO core-shell nanorod arrays are synthesized using a non-catalytic two-step annealing process of sputtered metal film on silicon wafer. The growth mechanism of the vertically aligned nanorod arrays are discussed. The NH3 sensing behaviors of the WO3-CuO core-shell arrays at different temperatures are reported. A possible NH3sensing mechanism for the hybrid is proposed.

The Semiconductor Industry Association (SIA), representing U.S. leadership in semiconductor manufacturing, design, and research, today announced worldwide sales of semiconductors reached $122.7 billion during the third quarter of 2018, an increase of 4.1 percent over the previous quarter and 13.8 percent more than the third quarter of 2017. Global sales for the month of September 2018 reached $40.9 billion, an uptick of 2.0 percent over last month’s total and 13.8 percent more than sales from June 2017. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average.

“Three-quarters of the way through 2018, the global semiconductor industry is on pace to post its highest-ever annual sales, comfortably topping last year’s record total of $412 billion,” said John Neuffer, president and CEO, Semiconductor Industry Association. “While year-to-year growth has tapered in recent months, September marked the global industry’s highest-ever monthly sales, and Q3 was its top-grossing quarter on record. Year-to-year sales in September were up across every major product category and regional market, with sales into China and the Americas continuing to lead the way.”

Regionally, sales increased compared to September 2017 in China (26.3 percent), the Americas (15.1 percent), Europe (8.8 percent), Japan (7.2 percent), and Asia Pacific/All Other (2.4 percent). Sales were up compared to last month in the Americas (6.0 percent), China (1.8 percent), and Europe (1.2 percent), but down slightly in Asia Pacific/All Other (-0.1 percent) and Japan (-0.6 percent).

For comprehensive monthly semiconductor sales data and detailed WSTS Forecasts, consider purchasing the WSTS Subscription Package. For detailed data on the global and U.S. semiconductor industry and market, consider purchasing the 2018 SIA Databook.

September 2018
Billions
Month-to-Month Sales
Market Last Month Current Month % Change
Americas 8.68 9.20 6.0%
Europe 3.53 3.57 1.2%
Japan 3.39 3.37 -0.6%
China 14.10 14.35 1.8%
Asia Pacific/All Other 10.43 10.42 -0.1%
Total 40.12 40.91 2.0%
Year-to-Year Sales
Market Last Year Current Month % Change
Americas 7.99 9.20 15.1%
Europe 3.28 3.57 8.8%
Japan 3.14 3.37 7.2%
China 11.36 14.35 26.3%
Asia Pacific/All Other 10.18 10.42 2.4%
Total 35.95 40.91 13.8%
Three-Month-Moving Average Sales
Market Apr/May/Jun Jul/Aug/Sept % Change
Americas 8.34 9.20 10.2%
Europe 3.67 3.57 -2.7%
Japan 3.39 3.37 -0.8%
China 13.59 14.35 5.6%
Asia Pacific/All Other 10.32 10.42 1.0%
Total 39.31 40.91 4.1%

Rice University scientists are counting on films of carbon nanotubes to make high-powered, fast-charging lithium metal batteries a logical replacement for common lithium-ion batteries.

Rice University graduate student Gladys López-Silva holds a lithium metal anode with a film of carbon nanotubes. Once the film is attached, it becomes infiltrated by lithium ions and turns red. Credit: Jeff Fitlow/Rice University

The Rice lab of chemist James Tour showed thin nanotube films effectively stop dendrites that grow naturally from unprotected lithium metal anodes in batteries. Over time, these tentacle-like dendrites can pierce the battery’s electrolyte core and reach the cathode, causing the battery to fail.

That problem has both dampened the use of lithium metal in commercial applications and encouraged researchers worldwide to solve it.

Lithium metal charges much faster and holds about 10 times more energy by volume than the lithium-ion electrodes found in just about every electronic device, including cellphones and electric cars.

“One of the ways to slow dendrites in lithium-ion batteries is to limit how fast they charge,” Tour said. “People don’t like that. They want to be able to charge their batteries quickly.”

The Rice team’s answer, detailed in Advanced Materials, is simple, inexpensive and highly effective at stopping dendrite growth, Tour said.

“What we’ve done turns out to be really easy,” he said. “You just coat a lithium metal foil with a multiwalled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.”

“Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions,” said Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva. “The ions distribute themselves throughout the nanotube film.”

When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.

The tangled-nanotube film effectively quenched dendrites over 580 charge/discharge cycles of a test battery with a sulfurized-carbon cathode the lab developed in previous experiments. The researchers reported the full lithium metal cells retained 99.8 percent of their coulombic efficiency, the measure of how well electrons move within an electrochemical system.

Air Liquide Advanced Materials Inc. was joined by local officials and members of the community to inaugurate a new speciality chemical production facility in Upper Mount Bethel, Pennsylvania, on October 19, 2018.

This new facility marks an expansion of Air Liquide’s operations in the community, adding 105,000 sq. ft. of production space. Featuring multiple manufacturing suites and updated infrastructure, the new site offers next generation specialty chemical operations that complement our global manufacturing base. Air Liquide worked closely with the Governor of Pennsylvania’s Action Team to reinforce its commitment to the region and bring this project to fruition.

Commented Paul Burlingame, President & CEO, Air Liquide Advanced Materials Inc.: “Air Liquide Advanced Materials is experiencing strong global growth, and the inauguration of the second state-of-the-art Advanced Materials Center in Upper Mount Bethel, Pennsylvania further enhances our ability to serve customers with innovative products and technologies. This facility comes to life thanks to the men and women of ALAM focused on safety, quality, and our customers along with the strong support of the Commonwealth of Pennsylvania, Lehigh Valley Economic Development Corporation, and the local Upper Mount Bethel community.”

Scientists from the NUST MISIS Laboratory of Inorganic Nanomaterials together with their international colleagues have proved it possible to change the structural and conductive properties of nanotubes by stretching them. This can potentially expand nanotubes’ application into electronics and high-precision sensors such as microprocessors and high-precision detectors. The research article has been published in Ultramicroscopy.

Carbon nanotubes can be represented as a sheet of graphene rolled in a special way. There are different ways of «folding» it, which leads to the graphene edges interconnecting at different angles, forming either armchair, zigzag or chiral nanotubes (Pic.1).

Nanotubes are considered to be promising materials for use in electronics and sensors because they have high electrical conductivity, which would work well in things like microprocessors and high-precision detectors. However, when producing carbon nanotubes it is hard to control their conductivity. Nanotubes with metallic and semiconducting properties can grow into a single array while microprocessor-based electronics require semiconducting nanotubes that have the same characteristics.

Scientists from the NUST MISIS Laboratory of Inorganic Nanomaterials jointly with a research team from Japan, China and Australia, led by Professor Dmitri Golberg, have proposed a method that allows for the modification of the structure of ready-made nanotubes and thus changes their conductive properties.

«The basis of the nanotube – a folded layer of graphene – is a grid of regular hexagons, the vertices of which are carbon atoms. If one of the carbon bonds in the nanotube is rotated by 90° degrees, a pentagon and a heptagon are formed at this [junction] instead of a hexagon, and a so-called Stone-Wales defect is obtained in this case. Such a defect can occur in the structure under certain conditions. Back in the late 90s, it was predicted that the migration of this defect along the walls of a highly heated nanotube with the application of mechanical stress could lead to a change in its structure – a sequential change in the chirality of the nanotube, which leads to a change in its electronic properties. No experimental evidence for this hypothesis has previously been obtained, but our research paper has presented convincing proof of it», said Associate Professor Pavel Sorokin, Doctor of Physical & Mathematical Sciences and head of the «Theoretical Materials Science of Nanostructures» infrastructure project at the NUST MISIS Laboratory of Inorganic Nanomaterials.

Scientists from the NUST MISIS Laboratory of Inorganic Nanomaterials have conducted simulations of the experiment at the atomic level. At first, the nanotubes were lengthened to form the first structural defect consisting of two pentagons and two heptagons (a Stone-Wales defect, pic.2a), where the prolonged lengthening of the tube began to «spread» to the sides, rearranging other carbon bonds (pic.2b). It was at this stage that the structure of the nanotubes changed. With further stretching, more and more Stone-Wales defects began to form, eventually leading to a change in the nanotubes’ conductivity (Pic. 2).

«We were responsible for the theoretical modeling of the process on a supercomputer in the NUST MISIS Laboratory for Modeling and Development of New Materials for the experimental part of the work. We are glad that the simulation results [support] the experimental data», added Dmitry Kvashnin, co-author of the research work, Candidate of Physical & Mathematical Sciences and a researcher at the NUST MISIS Laboratory of Inorganic Nanomaterials.

The proposed technology is capable of helping in the transformation of «metallic» nanotubes’ structure for their further application in semiconductor electronics and sensors such as microprocessors and ultrasensitive detectors.

Exagan, an innovator of gallium nitride (GaN) semiconductor technology enabling smaller and more efficient electrical converters, has established Exagan Taiwan Ltd. with a new sales and applications center in Taiwan – the company’s first step in its global market deployment – to accelerate the development and use of fast, intelligent GaN power solutions in the region.

The facility in Taipei’s Nankang Software Park officially opened today during ceremonies attended by Exagan’s president and CEO Frédéric Dupont, COO Fabrice Letertre and Asia sales director Ralf Kilguss. Kilguss is heading up regional sales in Asia, leveraging his 20 years of experience in the semiconductor and power electronics markets.

“With this new application center, our company experts will be able to work closely with local customers on evaluating and designing GaN-based solutions while speeding the technology’s adoption in the rapidly growing charger and server sectors, which are being driven by a very dynamic Asian market,” Dupont said.

Since its creation in 2014, Exagan has developed multiple partnerships in Asia to support its product design, development and manufacturing, thus establishing a robust supply chain with proven solutions for the targeted markets.

Earlier this year, Exagan launched its safe, powerful G-FET™ power transistors and G-DRIVE™ intelligent and fast-switching solution featuring an integrated driver and transistor in a single package. These are designed for easy system implementation in applications including servers and USB chargers.

The number of devices with at least one USB type C port for the simultaneous transfer of electrical power, data and video is forecasted to grow to nearly five billion units by 2021, according to market research firm IHS Markit, while total server shipments are expected to expand at a CAGR of 14 percent over the period of 2018 to 2023, as forecasted by Digitimes Research.

Graphene Flagship researchers have shown in a paper published in Science Advanceshow heterostructures built from graphene and topological insulators have strong, proximity induced spin-orbit coupling which can form the basis of novel information processing technologies.

Scanning Electron Microscope micrograph of a fabricated device showing the graphene topological insulator heterostructure channel. Credit: Dmitrii Khokhriakov, Chalmers University of Technology

Spin-orbit coupling is at the heart of spintronics. Graphene’s spin-orbit coupling and high electron mobility make it appealing for long spin coherence length at room temperature. Graphene Flagship researchers from Chalmers University of Technology (Sweden), Catalan Institute of Nanoscience and Nanotechnology – ICN2 (Spain), Universitat Autònoma de Barcelona (Spain) and ICREA Institució Catalana de Recerca i Estudis Avançats (Spain) showed a strong tunability and suppression of the spin signal and spin lifetime in heterostructures formed by graphene and topological insulators. This can lead to new graphene spintronic applications, ranging from novel circuits to new non-volatile memories and information processing technologies.

“The advantage of using heterostructures built from two Dirac materials is that, graphene in proximity with topological insulators still supports spin transport, and concurrently acquires a strong spin-orbit coupling,” said Associate Professor Saroj Prasad Dash, from Chalmers University of Technology.

“We do not just want to transport spin we want to manipulate it,” said Professor Stephan Roche from ICN2 and deputy leader of the Graphene Flagship’s spintronics Work-Package, “the use of topological insulators is a new dimension for spintronics, they have a surface state similar to graphene and can combine to create new hybrid states and new spin features. By combining graphene in this way we can use the tuneable density of states to switch on/off – to conduct or not conduct spin. This opens an active spin device playground.”

The Graphene Flagship, from its very beginning, saw the potential of spintronics devices made from graphene and related materials. This paper shows how combining graphene with other materials to make heterostructures opens new possibilities and potential applications.

“This paper combines experiment and theory and this collaboration is one of the strengths of the Spintronics Work-Package within the Graphene Flagship,” said Roche.

“Topological insulators belong to a class of material that generate strong spin currents, of direct relevance for spintronic applications such as spin-orbit torque memories. As reported by this article, the further combination of topological insulators with two-dimensional materials like graphene is ideal for enabling the propagation of spin information with extremely low power over long distances, as well as for exploiting complementary functionalities, key to further design and fabricate spin-logic architectures,” said Kevin Garello from IMEC, Belgium who is leader of the Graphene Flagships Spintronics Work-Package.

Professor Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship, and Chair of its Management Panel added “This paper brings us closer to building useful spintronic devices. The innovation and technology roadmap of the graphene Flagship recognises the potential of graphene and related materials in this area. This work yet again places the Flagship at the forefront of this field, initiated with pioneering contributions of European researchers.”

Organic semiconductor materials have the potential to be used in innovative applications such as transparent and flexible devices, and their low cost makes their potential use particularly attractive. The properties of organic semiconductor materials can be tuned by controlling their structure at the molecular level through parts of the structure known as electron-accepting units. A group of researchers centered at Osaka University has specifically tailored an electron-accepting unit that was then successfully used in an organic semiconductor applied in solar cell device that showed high photovoltaic performance. Their findings were published in NPG Asia Materials.

Chemical structures and photovoltaic characteristics. Credit: Osaka University

“Electron-accepting units are important elements of organic semiconductors,” study corresponding author Yoshio Aso says. “Through the controlled addition of electronegative fluorine groups to a widely used electron-accepting material, we were able to show precise control of the energy levels within the resulting semiconductor. This ability to tune the band gap translates to selectivity over the injection and transport of holes and/or electrons within the material, which is important in potential applications.”

The fluorinated electron-acceptor unit was used to prepare a thin film solar cell that was compared with a cell based on a non-fluorinated analogue. The researchers found that the fluorinated material showed enhanced power conversion efficiency, up to 3.12%. The morphology of the fluorinated film was also found to be good, which supported the efficient charge generation and transport that is necessary for successful application.

“The more we are able to fine tune organic semiconductor behavior on the molecular level, the more possibilities there will be for demonstrating their macroscopic applications,” co-author Yutaka Ie says. “It is our hope that the band gap control and high photovoltaic performance we have demonstrated will lead to our material being applied in devices such as organic light-emitted diodes, field-effect transistors, and thin film solar cells.”

The straightforward demonstration of the link between high electronegativity, greater electron-accepting tendency, and enhanced semiconductor performance, highlights both the potential and versatility of organic semiconductors. Further elegant solutions such as this one could substantially broaden the range of ƒÎ-conjugated materials, and reinforce the case for organic electronics.