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Grolltex Graphene Closes Oversubscribed Private Placement Financing Round

Posted By Graphene Council, The Graphene Council, Wednesday, September 11, 2019
Updated: Tuesday, September 10, 2019

Grolltex (named for ‘graphene-rolling-technologies’) is the largest commercial producer of single layer, ‘electronics grade’ graphene and graphene sensing materials in the U.S. They have announced that it has closed a non-brokered, oversubscribed private placement financing, in the form of a convertible note, with local area private investors. 

The gross proceeds of the private placement will be used for general working capital purposes and for increasing the capacity and quality testing capabilities of the company’s production facility in San Diego, California.

The company is focused on delivering inexpensive and enabling solutions to advanced nano-device and graphene sensor makers by fabricating the highest quality single layer graphene attainable, via chemical vapor deposition (or ‘CVD’).

The company is now capable of producing monolayer graphene sensors on large area plastic sheets at a cost of pennies per unit, in a high throughput and sustainable way.  Further, Grolltex is helping customers that currently produce their graphene sensors on silicon wafers, to transition that production capacity to making their sensors on large area sheets of biodegradable plastic instead, at a >100X cost savings. 

Monolayer graphene films are today seen as the most promising futuristic sensing materials for their combination of surface to volume ratio (the film is only one atom thick) and conductivity (the most conductive substance known at room temperature). Markets that are commercializing advanced sensors made of graphene include DNA sensing and editing, new drug discovery and wearable bio-monitors for glucose sensing and autonomous blood pressure monitoring via patches or watch-like wearable bracelet devices.

No securities were issued and no cash was paid as bonuses, finders’ fees, compensation or commissions in connection with the private placement.

Tags:  Biosensor  CVD  Graphene  Groltex  Sensors 

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Synthesizing single-crystalline hexagonal graphene quantum dots

Posted By Graphene Council, The Graphene Council, Monday, August 5, 2019
A KAIST team has designed a novel strategy for synthesizing single-crystalline graphene quantum dots, which emit stable blue light. The research team confirmed that a display made of their synthesized graphene quantum dots successfully emitted blue light with stable electric pressure, reportedly resolving the long-standing challenges of blue light emission in manufactured displays. The study, led by Professor O Ok Park in the Department of Chemical and Biological Engineering.

Graphene has gained increased attention as a next-generation material for its heat and electrical conductivity as well as its transparency. However, single and multi-layered graphene have characteristics of a conductor so that it is difficult to apply into semiconductor. Only when downsized to the nanoscale, semiconductor's distinct feature of bandgap will be exhibited to emit the light in the graphene. This illuminating featuring of dot is referred to as a graphene quantum dot.

Conventionally, single-crystalline graphene has been fabricated by chemical vapor deposition (CVD) on copper or nickel thin films, or by peeling graphite physically and chemically. However, graphene made via chemical vapor deposition is mainly used for large-surface transparent electrodes. Meanwhile, graphene made by chemical and physical peeling carries uneven size defects.

The research team explained that their graphene quantum dots exhibited a very stable single-phase reaction when they mixed amine and acetic acid with an aqueous solution of glucose. Then, they synthesized single-crystalline graphene quantum dots from the self-assembly of the reaction intermediate. In the course of fabrication, the team developed a new separation method at a low-temperature precipitation, which led to successfully creating a homogeneous nucleation of graphene quantum dots via a single-phase reaction.

Professor Park and his colleagues have developed solution phase synthesis technology that allows for the creation of the desired crystal size for single nanocrystals down to 100 nano meters. It is reportedly the first synthesis of the homogeneous nucleation of graphene through a single-phase reaction.

Professor Park said, "This solution method will significantly contribute to the grafting of graphene in various fields. The application of this new graphene will expand the scope of its applications such as for flexible displays and varistors."

This research was a joint project with a team from Korea University under Professor Sang Hyuk Im from the Department of Chemical and Biological Engineering, and was supported by the National Research Foundation of Korea, the Nano-Material Technology Development Program from the Electronics and Telecommunications Research Institute (ETRI), KAIST EEWS, and the BK21+ project from the Korean government.

Tags:  CVD  Graphene  KAIST  O Ok Park  quantum dots  Sang Hyuk Im 

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Graphene in Electronic Circuits

Posted By Graphene Council, The Graphene Council, Wednesday, July 31, 2019
Updated: Tuesday, July 30, 2019
Ever since graphene was discovered in 2004, researchers around the world have been working to develop commercially scalable applications for this high-performance material.

Graphene is 100 to 300 times stronger than steel at the atomic level and has a maximum electrical current density orders of magnitude greater than that of copper, making it the strongest, thinnest and, by far, the most reliable electrically conductive material on the planet. It is, therefore, an extremely promising material for interconnects, the fundamental components that connect billions of transistors on microchips in computers and other electronic devices in the modern world.

For over two decades, interconnects have been made of copper, but that metal encounters fundamental physical limitations as electrical components that incorporate it shrink to the nanoscale. “As you reduce the dimensions of copper wires, their resistivity shoots up,” said Kaustav Banerjee, a professor in the Department of Electrical and Computer Engineering. “Resistivity is a material property that is not supposed to change, but at the nanoscale, all properties change.”

As the resistivity increases, copper wires generate more heat, reducing their current-carrying capacity. It’s a problem that poses a fundamental threat to the $500 billion semiconductor industry. Graphene has the potential to solve that and other issues. One major obstacle, though, is designing graphene micro-components that can be manufactured on-chip, on a large scale, in a commercial foundry.

“Whatever the component, be it inductors, interconnects, antennas or anything else you want to do with graphene, industry will move forward with it only if you find a way to synthesize graphene directly onto silicon wafers,” Banerjee said. He explained that all manufacturing processes related to the transistors, which are made first, are referred to as the ‘front end.’ To synthesize something at the back-end — that is, after the transistors are fabricated — you face a tight thermal budget that cannot exceed a temperature of about 500 degrees Celsius. If the silicon wafer gets too hot during the back-end processes employed to fabricate the interconnects, other elements that are already on the chip may get damaged, or some impurities may start diffusing, changing the characteristics of the transistors.

Now, after a decade-long quest to achieve graphene interconnects, Banerjee’s lab has developed a method to implement high-conductivity, nanometer-scale doped multilayer graphene (DMG) interconnects that are compatible with high-volume manufacturing of integrated circuits. A paper describing the novel process was named one of the top papers at the 2018 IEEE International Electron Devices Meeting (IEDM),  from more than 230 that were accepted for oral presentations. It also was one of only two papers included in the first annual “IEDM Highlights” section of an issue of the journal Nature Electronics.

Banerjee first proposed the idea of using doped multi-layer graphene at the 2008 IEDM conference and has been working on it ever since. In February 2017 he led the experimental realization of the idea by Chemical Vapor Deposition (CVD) of multilayer graphene at a high temperature, subsequently transferring it to a silicon chip, then patterning the multilayer graphene, followed by doping. Electrical characterization of the conductivity of DMG interconnects down to a width of 20 nanometers established the efficacy of the idea that was proposed in 2008. However, the process was not “CMOS-compatible” (the standard industrial-scale process for making integrated circuits), since the temperature of CVD processes far exceed the thermal budget of back-end processes.

To overcome this bottleneck, Banerjee’s team developed a unique pressure-assisted solid-phase diffusion method for directly synthesizing a large area of high-quality multilayer graphene on a typical dielectric substrate used in the back-end CMOS process. Solid-phase diffusion, well known in the field of metallurgy and often used to form alloys, involves applying pressure and temperature to two different materials that are in close contact so that they diffuse into each other.

Banerjee’s group employed the technique in a novel way. They began by depositing solid-phase carbon in the form of graphite powder onto a deposited layer of nickel metal of optimized thickness. Then they applied heat (300 degrees Celsius) and nominal pressure to the graphite powder to help break down the graphite. The high diffusivity of carbon in nickel allows it to pass rapidly through the metal film.

How much carbon flows through the nickel depends on its thickness and the number of grains it holds. “Grains” refer to the fact that deposited nickel is not a single-crystal metal, but rather a polycrystalline metal, meaning it has areas where two single-crystalline regions meet each other without being perfectly aligned. These areas are called grain boundaries, and external particles — in this case, the carbon atoms — easily diffuse through them. The carbon atoms then recombine on the other surface of the nickel closer to the dielectric substrate, forming multiple graphene layers.

Banerjee’s group is able to control the process conditions to produce graphene of optimal thickness. “For interconnect applications, we know how many layers of graphene are needed,” said Junkai Jiang, a Ph.D. candidate in Banerjee’s lab and lead author of the 2018 IEDM paper. “So we optimized the nickel thickness and other process parameters to obtain precisely the number of graphene layers we want at the dielectric surface. “Subsequently, we simply remove the nickel by etching so that what’s left is only very high-quality graphene — virtually the same quality as graphene grown by CVD at very high temperatures,” he continued. “Because our process involves relatively low temperatures that pose no threat to the other fabricated elements on the chip, including the transistors, we can make the interconnects right on top of them.”

UCSB has filed a provisional patent on the process, which overcomes the obstacles that, until now, have prevented graphene from replacing copper. Bottom line: graphene interconnects help to create faster, smaller, lighter, more flexible, more reliable and more cost-effective integrated circuits. Banerjee is currently in talks with industry partners interested in potentially licensing this CMOS-compatible graphene synthesis technology, which could pave the way for what would be the first 2D material to enter the mainstream semiconductor industry.

Tags:  2D materials  CVD  Graphene  Graphite  Junkai Jiang  Kaustav Banerjee  Semiconductor  UC Santa Barbara 

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Step right up for bigger 2D sheets

Posted By Graphene Council, The Graphene Council, Thursday, March 7, 2019
Rice University researchers determined complementarity between growing hexagonal boron nitride crystals and a stepped substrate mimics the complementarity found in strands of DNA. The Rice theory supports experiments that have produced large, oriented wafers.

Very small steps make a big difference to researchers who want to create large wafers of two-dimensional material. Atom-sized steps in a substrate provide the means for 2D crystals growing in a chemical vapor furnace to come together in perfect rank. Scientists have recently observed this phenomenon, and now a Rice University group has an idea why it works.

Rice materials theorist Boris Yakobson and researcher Ksenia Bets led the construction of simulations that show atom-sized steps on a growth surface, or substrate, have the remarkable ability to keep monolayer crystal islands in alignment as they grow. If the conditions are right, the islands join into a larger crystal without the grain boundaries so characteristic of 2D materials like graphene grown via chemical vapor deposition (CVD). That preserves their electronic perfection and characteristics, which differ depending on the material.

Atom-sized steps in a substrate provide the means for 2D crystals growing in a chemical vapor furnace to come together in perfect rank. Scientists have recently observed this phenomenon, and now a Rice University group has an idea why it works.

Rice materials theorist Boris Yakobson and researcher Ksenia Bets led the construction of simulations that show atom-sized steps on a growth surface, or substrate, have the remarkable ability to keep monolayer crystal islands in alignment as they grow.

If the conditions are right, the islands join into a larger crystal without the grain boundaries so characteristic of 2D materials like graphene grown via chemical vapor deposition (CVD). That preserves their electronic perfection and characteristics, which differ depending on the material.

The Rice theory appears in the American Chemical Society journal Nano Letters.The investigation focused on hexagonal boron nitride (h-BN), aka white graphene, a crystal often grown via CVD. Crystals nucleate at various places on a perfectly flat substrate material and not necessarily in alignment with each other.

However, recent experiments have demonstrated that growth on vicinal substrates -- surfaces that appear flat but actually have sparse, atomically small steps -- can align the crystals and help them merge into a single, uniform structure, as reported on arXiv. A co-author of that report and leader of the Korean team, Feng Ding, is an alumnus of the Yakobson lab and a current adjunct professor at Rice.

But the experimentalists do not show how it works as, Yakobson said, the steps are known to meander and be somewhat misaligned.

"I like to compare the mechanism to a 'digital filter,' here offered by the discrete nature of atomic lattices," he said. "The analog curve that, with its slopes, describes a meandering step is 'sampled and digitized' by the very grid of constituent atomic rows, breaking the curve into straight 1D-terrace segments. The slope doesn't help, but it doesn't hurt. Surprisingly, the match can be good; like a well-designed house on a hill, it stands straight.

"The theory is simple, though it took a lot of hard work to calculate and confirm the complementarity matching between the metal template and the h-BN, almost like for A-G-T-C pairs in strands of DNA," Yakobson said.

It was unclear why the crystals merged into one so well until simulations by Bets, with the help of co-author and Rice graduate student Nitant Gupta, showed how h-BN "islands" remain aligned while nucleating along visibly curved steps.

"A vicinal surface has steps that are slightly misaligned within the flat area," Bets said. "It has large terraces, but on occasion there will be one-atom-high steps. The trick by the experimentalists was to align these vicinal steps in one direction."

In chemical vapor deposition, a hot gas of the atoms that will form the material are flowed into the chamber, where they settle on the substrate and nucleate crystals. h-BN atoms on a vicinal surface prefer to settle in the crook of the steps.

"They have this nice corner where the atoms will have more neighbors, which makes them happier," Bets said. "They try to align to the steps and grow from there.

"But from a physics point of view, it's impossible to have a perfect, atomically flat step," she said. "Sooner or later, there will be small indentations, or kinks. We found that at the atomic scale, these kinks in the steps don't prevent h-BN from aligning if their dimensions are complementary to the h-BN structure. In fact, they help to ensure co-orientation of the islands."

Because the steps the Rice lab modeled are 1.27 angstroms deep (an angstrom is one-billionth of a meter), the growing crystals have little trouble surmounting the boundary. "Those steps are smaller than the bond distance between the atoms," Bets said. "If they were larger, like two angstroms or higher, it would be more of a natural barrier, so the parameters have to be adjusted carefully."

Two growing islands that approach each other zip together seamlessly, according to the simulations. Similarly, cracks that appear along steps easily heal because the bonds between the atoms are strong enough to overcome the small distance.

Any path toward large-scale growth of 2D materials is worth pursuing for an army of applications, according to the researchers. 2D materials like conductive graphene, insulating h-BN and semiconducting transition metal dichalcogenides are all the focus of intense scrutiny by researchers around the world. The Rice researchers hope their theoretical models will point the way toward large crystals of many kinds.

The U.S. Department of Energy (DOE) supported the research. Computer resources were provided by the National Energy Research Scientific Computing Center, supported by the DOE Office of Science, and the National Science Foundation-supported DAVinCI cluster at Rice, administered by the Center for Research Computing and procured in partnership with Rice's Ken Kennedy Institute for Information Technology.

Tags:  Boris Yakobson  CVD  Graphene  Ksenia Bets  Rice University  U.S. Department of Energy (DOE) 

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Grolltex Drives Dramatic Increase of Single Layer CVD Graphene Production

Posted By Graphene Council, The Graphene Council, Monday, February 25, 2019
Updated: Monday, February 25, 2019

Graphene and 2D materials producer,Grolltex has completed its recent capacity expansion and released production for 30,000 eight-inch wafer equivalents per year at its CVD monolayer fabrication facility in San Diego, California. This ‘single atomic layer’ type of graphene is used in advanced electronics and other nano-devices and supports many use cases in wearables, IoT, photonics, semiconductors, biosensing and other next generation devices.

“This is the only commercial CVD monolayergraphene production facility in California and in fact it is the largest capacity plant of its kind in the U.S.”, said CEO, Jeff Draa. “Demand for our electronics grade graphene has never been better.  Our production lines are capable of producing single layer graphene or single layer hexagonal Boron Nitride”.
Otherwise known as ‘white graphene’, hexagonal Boron Nitride (or ‘hBN’) is the single atom thick insulator complement to graphene, which is a conductor.  The material hBN also has many other interesting characteristics, including being highly transparent, very strong, possesses anti-microbial and flame-retardantproperties and is additionally a performance accelerator for graphene.  The Grolltex factory expansion supports the growth, production and transfer of both of thesesingle layer materials.

“Maybe even more exciting, we currently have four active evaluations where our customers’advanced nano-factories are testing our graphene for use as the basis for their final devices and each factory eval is going very well”, said Draa.  “The biosensing area is an early adopter for our graphene, as evidenced by customers using our material to detect DNA, find diseases in blood, monitor glucose in sweat in the form of a wearable patch and validating the safety and efficacy of new drugs in previously unthinkably short times and low costs.”

Grolltex, short for ‘graphene-rolling-technologies’, makes large area, single atom thick graphene sheets using chemical vapor deposition or ‘CVD’; essentially the process is depositing gas in a chamber, then allowing it to cool, which leaves a continuous one atom thick layer of carbon on a target substrate.  This type of graphene is highly valued for its electrical characteristics, strength and flexibility and some see it as‘next generation silicon’.

The company uses patented research and techniques initially developed at the University of California, San Diego, to produce high quality, single layer graphene, hexagonal Boron Nitride and other 2D materials and products.  The company is a practitioner of, and specializes in, exclusively sustainable graphene production methods and is committed to advancing the field of graphene to improve the future of leading-edge materials science and product design through the optimization of single atom thick materials.

Tags:  Biosensor  CVD  Graphene  Grolltex  Jeff Draa  Sensors 

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Graphene Commercialization Conference in Berlin

Posted By Graphene Council, The Graphene Council, Thursday, February 21, 2019

Like many advanced materials, there is a significant learning curve to advance promising lab results into real commercial products. This includes a learning experience from the manufacturer, for cost-effective high-volume production, and a learning experience for the end-user, to establish the value and utilization of this novel material.   

IDTechEx have been following the graphene market throughout this learning experience, and the 13th edition of their commercially focussed B2B graphene conference, Graphene & 2D Materials, will be held from 10 - 11 April 2019 in Berlin, Germany. 

Once again, The Graphene Council will be there to help educate stakeholders on the value that graphene enhanced materials deliver, as well as to publicly announce the launch of the Verified Graphene Producer program. 

During the previous 12 conferences, the attendees have heard from all the main market players and end-users, with key market announcements made and technical insights provided. As the market reaches a turning point, this becomes more significant as the headlines have greater global impact.   

This combined conference and exhibition stands at a crucial point in the history of the graphene market. As laid out in a previous article, attendees will hear many relevant talks including those from: BASF, Sixth Element, NanoXplore, Avanzare, Sixonia Tech, Mitsubishi Electric, Samsung, First Graphene, and many more.   

Below are some selected indicators that the hype is turning to commercial reality for graphene. This includes the breaking of the scale vs orders dilemma, notable use-cases as a heat spreader, polymer additive, corrosion resistant coating, or enhanced battery electrode, and the upturn in investment and acquisitions. The specific news and outcomes for these indicators have all been seen at this world leading conference series and will continue to be added into the 2019 events.

2D materials are a diverse family, the event will include presentations on graphene nanoplatelets, graphene oxide (GO), reduced graphene oxide (rGO), and CVD graphene films. This includes perspectives and advancements multiple sections of the current and future supply chain: 

Material manufacturing: Attendees will hear from both established manufacturers looking to scale-up proceedings and new entries. For example, this includes NanoXplore and their 10,000 tpa plant announcement and Sixonia Tech a German university spin-out company working on electrochemical exfoliation. 

Intermediary formation: suspensions, polymer masterbatches and more are the most useful form of graphene-based products for many end-users. Attendees will hear more about this important step throughout the presentations. For example, Avanzare will discuss masterbatches for the polymer composite industry and Sixth Element provide suspensions to form heat spreaders and coatings. 

Integration and end-use application: How the materials are used, and the potential applications are very diverse. The conference will cover this in many applications from the use in energy storage, to polymer additives, electronic devices, thermal interface materials, and more all in discussion. 

Material sourcing and market opportunities: Many graphite mining companies are moving downstream and investing heavily to make this market a success. First Graphene are one such example of a vertically integrated company that will be presenting. Similarly, large materials companies are partnering or positioning themselves to utilise graphene products. Delegates will hear detailed analysis and perspectives of this industry from numerous speakers including from the likes of BASF.

For more information, please visit. 

Tags:  Avanzare  BASF  CVD  First Graphene  Graphene  Mitsubishi Electric  NanoXplore  rGO  Samsung  Sixonia Tech  Sixth Element 

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Open-source automated chemical vapor deposition system for the production of two-dimensional nanomaterials

Posted By Graphene Council, The Graphene Council, Wednesday, January 30, 2019
Updated: Tuesday, January 29, 2019
A research group at Boise State University led by Assistant Professor David Estrada of the Micron School of Materials Science and Engineering has released the open-source design of a chemical vapor deposition (CVD) system for two-dimensional (2D) materials growth, an advance which could lower the barrier of entry into 2D materials research and expedite 2D materials discovery and translation from the benchtop to the market.

2-dimensional materials are a class of materials that are one to a few atoms thick. The pioneering work of Nobel Laureates Andre Geim and Konstantin Novoselov in isolating and measuring the physical properties of graphene – a 2D form of carbon arranged in a hexagonal crystal structure - ignited the field of 2D materials research

While 2D materials can be obtained from bulk van der Waals crystals (e.g. graphite and MoS2) using a micromechanical cleavage approach enabled by adhesive tapes, the community quickly realized that unlocking the full potential of 2D materials would require advanced manufacturing methods compatible with the semiconductor industry’s infrastructure.

Chemical vapor deposition is a promising approach for scalable synthesis of 2D materials – but automated commercial systems can be cost prohibitive for some research groups and startup companies. In such situations students are often tasked with building custom furnaces, which can be burdensome and time consuming. While there is value in such endeavors, this can limit productivity and increase time to degree completion.

A recent trend in the scientific community has been to develop open-source hardware and software to reduce equipment cost and expedite scientific discovery. Advances in open-source 3-dimensional printing and microcontrollers have resulted in freely available designs of scientific equipment ranging from test tube holders, potentiostats, syringe pumps and microscopes. Estrada and his colleagues have now added a variable pressure chemical vapor deposition system to the inventory of open-source scientific equipment.

“As a graduate student I was fortunate enough that my advisor was able to purchase a commercial chemical vapor deposition system which greatly impacted our ability to quickly grow carbon nanotubes and graphene. This was critical to advancing our scientific investigations,” said Estrada. “When I read scientific articles I am intrigued with the use of the phrase “custom-built furnace” as I now realize how much time and effort graduate students invest in such endeavors.”

The design and qualification of the furnace was accomplished by lead authors Dale Brown, a former Micron School of Materials Science and Engineering graduate student, and Clinical Assistant faculty member Lizandra Godwin, with assistance from the other co-authors. The results of their variable pressure CVD system have been published in PLoS One ("Open-source automated chemical vapor deposition system for the production of two- dimensional nanomaterials") and include the parts list, software drivers, assembly instructions and programs for automated control of synthesis procedures. Using this furnace, the team has demonstrated the growth of graphene, graphene foam, tungsten disulfide and tungsten disulfide – graphene heterostructures.

“Our goal in publishing this design is to alleviate the burden of designing and constructing CVD systems for the early stage graduate student,” said Godwin. “If we can save even a semester of time for a graduate student this can have a significant impact on their time to graduation and their ability to focus on research and advancing the field.”

“We hope others in the community can improve on our design by incorporating open-source software for automated control of 2D materials synthesis,” said Estrada. “Such an improvement could further reduce the barrier to entry for 2D materials research.”

Tags:  2D materials  Boise State University  CVD  Graphene 

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Graphene hits the right note at high frequencies

Posted By Graphene Council, The Graphene Council, Tuesday, January 15, 2019

Graphene holds the potential to deliver a new generation of ultrafast electronic devices. Current silicon technology can achieve clock rates – a measure of how fast devices can switch – of several hundred gigahertz (GHz). Graphene could achieve clock rates up to a thousand times faster, propelling electronics into the terahertz (THz) range. But, until now, graphene’s ability to convert oscillating electromagnetic signals into higher frequency modes has been just a theoretical prediction.

Now researchers from the Helmholtz Zentrum DresdenRossendorf (HZDR) and University of Duisburg-Essen (UDE), in collaboration with the director of the Max Planck Institute for Polymer Research (MPI-P) Mischa Bonn and other researchers, have shown that graphene can covert high frequency gigahertz signals into the terahertz range [Hafez et al., Nature (2018)].

“We have been able to provide the first direct proof of frequency multiplication from gigahertz to terahertz in a graphene monolayer and to generate electronic signals in the terahertz range with remarkable efficiency,” explain Michael Gensch of HZDR and Dmitry Turchinovich of UDE.

Using the novel superconducting accelerator TELBE terahertz radiation source at HZDR’s ELBE Center for High-Power Radiation Sources, the researchers bombarded chemical vapor deposition (CVD)-produced graphene with electromagnetic pulses in the frequency range 300–680 GHz. As previous theoretical calculations have predicted, the results show that graphene is able to convert these pulses into signals with three, five, or seven times the initial frequency, reaching the terahertz range.

“We were not only able to demonstrate a long-predicted effect in graphene experimentally for the first time, but also to understand it quantitatively at the same time,” points out Turchinovich.

By doping the graphene, the researchers created a high proportion of free electrons or a so-called Fermi liquid. When an external oscillating field excites these free electrons, rather like a normal liquid, they heat up and share their energy with surrounding electrons. The hot electrons form a vapor-like state, just like an evaporating liquid. When the hot Fermi vapor phase cools, it returns to its liquid form extremely quickly. The transition back and forth between these vapor and liquid phases in graphene induces a corresponding change in its conductivity. This very rapid oscillation in conductivity drives the frequency multiplication effect.

“In theory, [this] should allow clock rates up to a thousand times faster than today’s silicon-based electronics,” say Gensch and Turchinovich.

The conversion efficiency of graphene is at least 7–18 orders of magnitude more efficient than other electronic materials, the researchers point out. Since the effect has been demonstrated with mass-produced CVD graphene, they believe there are no real obstacles to overcome other than the engineering challenge of integrating graphene into circuits.

“Our discovery is groundbreaking,” says Bonn. “We have demonstrated that carbon-based electronics can operate extremely efficiently at ultrafast rates. Ultrafast hybrid components made of graphene and traditional semiconductors are also now conceivable.”

Nathalie Vermeulen, professor in the Brussels Photonics group (B-PHOT) at Vrije Universiteit Brussel (VUB) in Belgium, agrees that the work is a major breakthrough.

“The nonlinear-optical physics of graphene is an insufficiently understood field, with experimental results often differing from theoretical predictions,” she says. “These new insights, however, shine new light on the nonlinear-optical behavior of graphene in the terahertz regime.”

The researchers’ experimental findings are clearly supported by corresponding theory, Vermeulen adds, which is very convincing.

“It is not often that major advances in fundamental scientific understanding and practical applications go hand in hand, but I believe it is the case here,” she says. “The demonstration of such efficient high-harmonic terahertz generation at room temperature is very powerful and paves the way for concrete application possibilities.”

The advance could extend the functionality of graphene transistors into high-frequency optoelectronic applications and opens up the possibility of similar behavior in other two-dimensional Dirac materials. Marc Dignam of Queen’s University in Canada is also positive about the technological innovations that the demonstration of monolayer graphene’s nonlinear response to terahertz fields could open up.

“The experiments are performed at room temperature in air and, given the relatively short scattering time, it is evident that harmonic generation will occur for relatively moderate field amplitudes, even in samples that are not particularly pristine,” he points out. “This indicates that such harmonic generation could find its way into future devices, once higher-efficiency guiding structures, such as waveguides, are employed.”

He believes that the key to the success of the work is the low-noise, multi-cycle terahertz source (TELBE) used by the researchers. However, Dignam is less convinced by the team’s theoretical explanation of graphene’s nonlinear response. No doubt these exciting results will spur further microscopic theoretical investigations examining carrier dynamics in graphene in more detail.

Tags:  CVD  Electronics  Graphene  graphene production  Terahertz 

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Novel Production Technique Offers Start-up New Approach to Markets

Posted By Dexter Johnson, IEEE Spectrum, Thursday, December 20, 2018

California-based NTherma is leveraging a proprietary graphene production method based on the unzipping of multiwalled carbon nanotubes into graphene nanoplatelets or nanoribbons.

The backgrounds of NTherma’s co-founders Cattien V. Nguyen, President & CEO, and Thuy Ngo, VP Business Developments & Investor Relations, cover both the science of graphene as well as its business development. Nguyen’s background contains some of the heavy hitters in nanomaterials research over the last 20 years: IBM Almaden Research Center and Stanford University.

With their manufacturing process offering a high degree of customization, NTherma is targeting applications that exploit this inherent flexibility that other manufacturing techniques can’t so easily deliver on.

As a new Corporate Member of The Graphene Council, we got the opportunity to ask them about how they are approaching the market with their novel manufacturing technique, some of the challenges they are facing and how they plan to overcome them.

 Q: Could you provide us more details about your method for producing graphene? It appears from your website that it may be a bottom-up approach. Is it a CVD-enabled process or direct chemical synthesis? And what kind of graphene does it produce?

Our graphene production method is different from the two current production processes.  We don't produce graphene by CVD of single layer directly on a metal substrate and we don't produce graphene by exfoliating graphite.  Both of these production methods have a number of tradeoffs including cost, purity, and control of structural parameters.

NTherma's unique approach to the production of graphene starts with our patent-pending method of producing carbon nanotubes (CNTs) that have high purity and high degree control of lengths and diameters, and most importantly a much lower production cost.  NTherma's graphene is then derived by the chemical conversion of high quality CNTs. 

Depending on the degree of chemical oxidation process, the produced graphene can be nanoplatelets or nanoribbons, or a combination of the two types.  Our ability to control the CNT length and their high purity together translates to high quality graphene at a much lower cost.  Of particularly importance is the availability of graphene nanoribbons at a large scale with controlled length, high purity, and much lower cost. This will open up a number of applications not currently feasible with commercially available graphene.

Could you let us know what applications you are targeting for your graphene? And can you tell us a bit about how you came to target these applications?

We are currently focusing on the following applications:

1.  Graphene for Oil Additives:  These reduce engine friction, improved fuel efficiency and lower emissions.  We differentiate our graphene as an oil additive in that our graphene forms a stable dispersion in oil with a demonstrated shelf life of greater than 12 months.

2.  Coatings:  There are many coating applications employing graphene and currently we are working with a few partners to integrate our graphene products.  We are also focusing on applications such as touchscreen and display as well as smart windows that other graphene materials have not been able to effectively address. 

3.  Lithium-ion (Li-ion) Batteries:  Preliminary test results are positive.  We're looking for partners to continue developing and testing the process. 

Because of our unique customization ability, we can alter length, layers and uniformity of our graphene per customers' requests.  Realizing that our high quality and consistent materials can unlock previous bottlenecks that other graphene products couldn't resolve, we chose these applications in the order provided as we see these applications and markets having the highest potential and where our technology will have the highest impact.

You are also producing multi-walled carbon nanotubes (MWCNTs). How do you see this fitting with your graphene production?

We produce MWCNTs for several other applications such as thermal management and also carbon nanotube yarns in development with a commercial partner. 

We also produce our graphene by the chemical conversion of MWNTs.

Is your strategy to remain a graphene and MWCNT producer, or do you see yourself moving further up the value chain to make devices from these materials?

We will focus on scaling up the production of high quality MWCNTs and graphene for the near future.  At the same time, we are developing, or have plans to develop, other applications and markets by ourselves or with partners in order to add more value to our business by strategically positioning our unique technology in a variety of verticals.

What do you see as the greatest challenge for your business in making an impact the commercialization of graphene, i.e. customer education, lack of standards, etc.? And what do you believe can be done to overcome these challenges?

The greatest challenges as a business for us have been our efforts to work with the end users and to understand as well as to educate the potential customers of our unique graphene products for any particular applications and product development processes.  Not all graphene products are the same in their purity, structural parameters such as size and number of layers, and cost.  These facts have to be made known to the end users and have to match with the end user's specific application.

Additionally, we also have to overcome clients' negative experiences with using other producers' inconsistent quality products.  We have to resolve these issues by continuing to work closely with our potential customers and partners by helping them to understand the materials and also optimizing and testing products for specific applications ourselves to provide clients with testing procedures and data (both in a lab environment and in real life).

Tags:  carbon nanotubes  coatings  CVD  Li-ion batteries  lubricants 

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Grolltex Releases ‘Enhanced Performance Graphene’ for Electronic Devices

Posted By Terrance Barkan, Monday, October 15, 2018

San Diego based graphene and 2D materials producer Grolltex has completed characterization and is releasing for commercial sale a configuration of large area, single layer graphene that exhibits dramatically improved ‘electron mobility’, which translates to better graphene performance.  This ‘heterostructure’ contains a layer or layers of hexagonal Boron Nitride (or ‘hBN’) underneath graphene, enabling enhanced graphene capabilities.  

Grolltex has begun commercial pre-sales to customers of this ‘Enhanced Performance Graphene’ product, which can significantly improve device performance for sensing, transistors, connectivity and other key aspects of nano-devices.  This type of material performance improvement is often a stepping stone for new applications enabling large market growth toward faster, smaller, cheaper and more sensitive silicon-based devices.

“The data back from our large European device partner showed carrier mobility performance improvements starting at 30%, and our internal work shows us that with some configuration adjustments, we can even build on this toward electron mobility improvements in exponential regimes”, said Jeff Draa, Grolltex CEO and co-founder.  “We believe this is going to be incredibly important to many of our customers that build things on silicon”.

The first reason for the improvement of graphene electron mobility performance, when layered on top of hBN on a wafer, is that the underlying layer of hBN, between the wafer and the graphene, planarizes the surface of the silicon wafer and allows graphene to sit on a surface (hBN) far more conducive to graphene electron flow.  

Another reason has to do with the electron interference of the oxide coming out of the underlying Si/SiO2 wafer, if graphene sits directly on top of it.  With the hBN layer between the graphene and the wafer, the negative effect of the oxide from the wafer on graphene electron performance is greatly reduced, allowing a much freer flow of graphene electrons.  Additional advantages are lower processing temperatures and a much stronger adhesion of the graphene layer to the underlying substrate, with hBN present.

“So, when graphene sits on hBN, it performs much closer to the theoretical ‘electron superhighway’ that graphene users expect”, according to Draa. “We have characterized and are selling this heterostructure to our pre-qualified customers in up to 8” (200mm) diameter configurations and can layer hBN and graphene in any combination”. 

“Device designers, especially advanced sensor makers, are really keyed in to electron mobility. There are many variables that affect this and he who can square those away and show dramatic improvements in mobility can help add real, unique and substantial value to device performance”, said Draa. “Next on our characterization list is MoS2, which is an important ‘band-gap’ material that has been missing in 2D offerings.”

Grolltex, short for ‘graphene-rolling-technologies’, uses patented research and techniques initially developed at the University of California, San Diego, to produce high quality, single layer graphene, hexagonal Boron Nitride and other 2D materials and products.  The company is a practitioner of, and specializes in, exclusively sustainable graphene production methods and is committed to advancing the field of graphene to improve the future of leading edge materials science and product design through the optimization of single atom thick materials.

About Grolltex:

Grolltex, Inc., is a nanotechnology materials, products and equipment company focusing on the optimization and advancement of the key monolayer material ‘graphene’ and related 2D materials.  The company holds a number of strategic patents and technological advantages in areas relating to the manufacture of high quality, monolayer ‘CVD’ graphene and hexagonal Boron Nitride as well as on several advanced products made of graphene and 2D materials, such as hyper efficient solar cells, next generation sensors, advanced fuel cells and futuristic super-thin and flexible displays for use in wearables, smart phones and other electronics.  

For complete information, please visit:


Media Contact:

Attn: Media Relations, Grolltex, Inc.

10085 Scripps Ranch Court, Suite D

San Diego, CA 92131

Tags:  CVD  Electronics  Graphene  Grolltex  HbN  Jeff Draa 

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