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New studies on particle entanglement dynamics in graphene for alternative quantum computing protocols

Posted By Graphene Council, Thursday, September 10, 2020
Quantum properties of matter as entanglement, which can allow controlling quantum states of physical systems, are key to the development of quantum computing and higher-performance information processing. Entanglement usually defines a nonlocal correlation between two or more particles, such that the quantum state of each of them cannot be described independently of the state of the others, even when particles become separated by an extremely large distance. Entanglement can be also observed between internal degrees of freedom of a single particle, which are independent parameters describing the state of a system, as physical coordinates define the position of a point in space. The comprehension of these phenomena, called inter- and intra-particle entanglement, can lead to manipulating the quantum states of physical systems, including materials as graphene and topological matter as a whole. 

In a paper recently published in Physical Review B as a Rapid Communication, researchers from the ICN2 Theoretical and Computational Nanoscience group, led by ICREA Prof. Stephan Roche, present a study on the origin, dynamics and magnitude of intra-particle entanglement between various degrees of freedom of electrons propagating in graphene. In particular, they explore the quantum correlations between the spin, defined as the intrinsic angular momentum of particles, and the pseudo-spin, which is a property analogous to spin that emerges in lattice structures and depends on their specific geometrical symmetries.

The authors of this study show that large intra-particle entanglement is a general feature of graphene supported onto a substrate and that its generation and evolution is independent of the initial state of the system. In addition, it may be robust to disorder and dephasing, which means that, if an interaction compromised the intra-particle entanglement, it would regenerate. This research also suggests that the properties of intra-particle entanglement in graphene should be relevant to the dynamic of inter-particle entanglement between pairs of electrons: in fact, the evolution of the first phenomenon is reflected in the second. Because of this, intra-particle entanglement might be detected indirectly in experiments via inter-particle correlations.

These results unveil unexplored paths to understanding and manipulating entanglement phenomena in a family of materials, called Dirac materials, which includes graphene: this name is due to the fact that they are systems that can be described by the Dirac equation of relativistic quantum mechanics. The ability to detect and manipulate entanglement in such materials could become an unprecedented resource for future research on the application of this phenomenon to quantum information processing.

Tags:  Graphene  ICN2  ICREA  quantum materials  Stephan Roche 

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First look inside new £105m Henry Royce Institute Hub Building

Posted By Graphene Council, Thursday, September 10, 2020
The Henry Royce Institute for advanced materials research and innovation celebrated a key milestone earlier this year ahead of the new national hub becoming fully operational in 2021.

The Royce Hub Building based at The University of Manchester forms part of a growing network of facilities across the Institute’s Partner organisations: the National Nuclear Laboratory, UK Atomic Energy Authority, Imperial College London and the Universities of Cambridge, Leeds, Liverpool, Oxford and Sheffield, providing access to state-of-the-art equipment to academia and industry.

Extending across 9 floors and located at the heart of The University of Manchester's campus, it will foster world-class collaborative research in tandem with industry to act as an international convener for materials research excellence.

Following the construction phase, the Royce Hub Building was handed over by the contractors Laing O’Rourke in March 2020 and the first operational staff were just hours away from moving in before non-essential facilities closure was initiated in line with government guidance.

Progress on the interiors still continues and the Institute can now share a first look inside the £105m building which will act as a national hub for driving advanced materials research, development, and commercialisation in the UK.

Contractors continue the fit-out to minimise disruption when equipment and staff move in following The University of Manchester’s phased reopening of the campus. The first labs are expected to be completed towards the end of 2020.

The building will host £45 million worth of new equipment, as well as existing facilities in Manchester for biomedical materials, metals processing, digital fabrication, and sustainable materials research including the new Sustainable Materials Innovation Hub part-funded by the European Regional Development Fund. Alongside this will be collaborative space for industry engagement, helping to accelerate the development and commercialisation of advanced materials for a sustainable society.

The building and new equipment, totalling £150 million, forms part of the wider £235m investment by the Engineering & Physical Sciences Research Council across Royce’s national partnership. Investment has also be made by The Wolfson Foundation to support the biomedical materials facility within the building.

“The new Royce Hub Building will act as a centre of scientific excellence for advanced materials and a meeting place for the national community. By bringing together the UK’s academic and industrial materials leaders, Royce will identify new opportunities, workshop ideas, and develop new strategies and approaches to tomorrow’s materials demands.” Prof Philip Withers, Regius Professor of Materials and Royce Chief Scientist

Regius Professor of Materials and Royce Chief Scientist Philip Withers said: “The new Royce Hub Building will act as a centre of scientific excellence for advanced materials and a meeting place for the national community. By bringing together the UK’s academic and industrial materials leaders, Royce will identify new opportunities, workshop ideas, and develop new strategies and approaches to tomorrow’s materials demands.”

Professor David Knowles, CEO of the Henry Royce Institute said: “Royce has come a long way since its inception in 2016 and the handover of the new Royce Hub Building in Manchester represents the next chapter in our story. Although COVID-19 has delivered some unprecedented challenges and delays, we are confident that the physical space will demonstrate that the national institute is truly open for business. We can now look to address challenge-led research that will have positive impact on UK and global citizens, underpinning the Royce vision of ‘Advanced Materials for a Sustainable Society’.”

Manchester is a world-leader in developing new and existing materials and is already known globally as the home of graphene – a game-changing two-dimensional material first isolated at The University of Manchester in 2004.

Dr Diana Hampson, Director of Estates for The University of Manchester commented “We are delighted to have successfully delivered the construction phase of the Henry Royce Institute Hub Building which sits alongside the University’s growing advanced materials campus including the National Graphene Institute and the Graphene Engineering Innovation Centre. The research that will take place in these buildings will consolidate Manchester’s role at the centre of materials characterisation – measuring and exploring materials that will help us fully understand their properties and potential.”

Professor Dame Lynn Gladden, EPSRC Executive Chair said: “Advanced materials research and innovation is essential to tackle global challenges from applications in the energy sector to advances in healthcare. The opening of the new Royce Hub Building is an important milestone to drive exciting advanced materials research that will extend our capabilities across a wide range of disciplines.”

The Royce Hub Building, under the Project and Cost Management of Arcadis was designed by NBBJ, an international architectural practice, alongside civil and structural engineers Ramboll and building services engineers Arup. The building was delivered by Laing O’Rourke, the appointed University of Manchester contractor.

Tags:  Dame Lynn Gladden  David Knowles  Diana Hampson  Graphene  Philip Withers  The Henry Royce Institute  University of Manchester 

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Paving the way for tunable graphene plasmonic THz amplifiers

Posted By Graphene Council, Wednesday, September 9, 2020
Tohoku University Professor Taiichi Otsuji has led a team of international researchers in successfully demonstrating a room-temperature coherent amplification of terahertz (THz) radiation in graphene, electrically driven by a dry cell battery.

Roughly 40 years ago, the arrival of plasma wave electronics opened up a wealth of new opportunities. Scientists were fascinated with the possibility that plasma waves could propagate faster than electrons, suggesting that so-called "plasmonic" devices could work at THz frequencies. However, experimental attempts to realize such amplifiers or emitters remained elusive.

"Our study explored THz light-plasmon coupling, light absorption, and amplification using a graphene-based system because of its excellent room-temperature electrical and optical properties," said Professor Otsuji who is based at the Ultra-Broadband Signal Processing Laboratory at Tohoku University's Research Institute of Electrical Communication (RIEC).

The research team, which consisted of members from Japanese, French, Polish and Russian institutions, designed a series of monolayer-graphene channel transistor structures. These featured an original dual-gathering gate that worked as a highly efficient antenna to couple the THz radiations and graphene plasmons.

Using these devices allowed the researchers to demonstrate tunable resonant plasmon absorption that, with an increase in current, results in THz radiation amplification. The amplification gain of up to 9% was observed in the monolayer graphene -- far beyond the well-known landmark level of 2.3% that is the maximum available when photons directly interact with electrons without excitation of graphene plasmons.

To interpret the results, the research team used a dissipative plasmonic crystal model, capturing the main trends and basic physics of the amplification phenomena. Specifically, the model predicts the increase in the channel dc current that drives the system into an amplification regime. This indicates that the plasma waves may transfer the dc energy into the incoming THz electromagnetic waves in a coherent fashion.

"Because all results were obtained at room temperature, our experimental results pave the way toward further THz plasmonic technology with a new generation of all-electronic, resonant, and voltage-controlled THz amplifiers," added Professor Otsuji.

Tags:  Battery  Graphene  Taiichi Otsuji  Tohoku University 

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A tiny instrument to measure the faintest magnetic fields

Posted By Graphene Council, Wednesday, September 9, 2020

Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields. At the heart of the superconducting quantum interference device are two atomically thin layers of graphene, which the researchers combined with boron nitride. Instruments like this one have applications in areas such as medicine, besides being used to research new materials.

To measure very small magnetic fields, researchers often use superconducting quantum interference devices, or SQUIDs. In medicine, their uses include monitoring brain or heart activity, for example, while in the earth sciences researchers use SQUIDs to characterize the composition of rocks or detect groundwater flows. The devices also have a broad range of uses in other applied fields and basic research.

The team led by Professor Christian Schönenberger of the University of Basel's Department of Physics and the Swiss Nanoscience Institute has now succeeded in creating one of the smallest SQUIDs ever built. The researchers described their achievement in the scientific journal Nano Letters.

A superconducting ring with weak links

A typical SQUID consists of a superconducting ring interrupted at two points by an extremely thin film with normal conducting or insulating properties. These points, known as weak links, must be so thin that the electron pairs responsible for superconductivity are able to tunnel through them. Researchers recently also began using nanomaterials such as nanotubes, nanowires or graphene to fashion the weak links connecting the two superconductors.

As a result of their configuration, SQUIDs have a critical current threshold above which the resistance-free superconductor becomes a conductor with ordinary resistance. This critical threshold is determined by the magnetic flux passing through the ring. By measuring this critical current precisely, the researchers can draw conclusions about the strength of the magnetic field.

SQUIDs with six layers

"Our novel SQUID consists of a complex, six-layer stack of individual two-dimensional materials," explains lead author David Indolese. Inside it are two graphene monolayers separated by a very thin layer of insulating boron nitride. "If two superconducting contacts are connected to this sandwich, it behaves like a SQUID - meaning it can be used to detect extremely weak magnetic fields."

In this setup, the graphene layers are the weak links, although in contrast to a regular SQUID they are not positioned next to each other, but one on top of the other, aligned horizontally. "As a result, our SQUID has a very small surface area, limited only by the constraints of nanofabrication technology," explains Dr. Paritosh Karnatak from Schönenberger's team.

The tiny device for measuring magnetic fields is only around 10 nanometers high - roughly a thousandth of the thickness of a human hair. The instrument can trigger supercurrents that flow in minuscule spaces. Moreover, its sensitivity can be adjusted by changing the distance between the graphene layers. With the help of electrical fields, the researchers are also able to increase the signal strength, further enhancing the measurement accuracy.

Analyzing topological insulators

The Basel research team's primary goal in developing the novel SQUIDs was to analyze the edge currents of topological insulators. Topological insulators are currently a focus of countless research groups all over the world. On the inside, they behave like insulators, while on the outside - or along the edges - they conduct current almost losslessly, making them possible candidates for a broad range of applications in the field of electronics.

"With the new SQUID, we can determine whether these lossless supercurrents are due to a material's topological properties, and thereby tell them apart from non-topological materials. This is very important for the study of topological insulators," remarked Schönenberger of the project. In future, SQUIDs could also be used as low-noise amplifiers for high-frequency electrical signals, or for instance to detect local brainwaves (magnetoencephalography), as their compact design means a large number of the devices can be connected in series.

Tags:  Christian Schönenberger  David Indolese  Graphene  Healthcare  nanomaterials  Paritosh Karnatak  University of Basel 

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A torchbearer for the future of applied materials and optoelectronics — Professor Chen Hsiang

Posted By Graphene Council, Wednesday, September 9, 2020
For those unfamiliar with the terms “applied materials” and “optoelectronic engineering,” a few keywords such as “semiconductors” and “sensors” should jolt one’s memory. The importance of this cutting-edge field can be illustrated by examining recent Nobel Prize winners and their research.

First, three Japanese researchers were jointly awarded the 2014 Nobel Prize for Physics "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources," for they held the key to the elusive blue LED — Gallium nitride (GaN).

Another pair of laureates, both of Russian heritage, were awarded in 2010 "for groundbreaking experiments regarding the two-dimensional material graphene." Graphene is a newly discovered form of carbon that is prized by manufacturers of touchscreens, light panels, and solar cells for its superior transparency and heat-conducting properties.

Chen Hsiang, chair of National Chi Nan University’s Department of Applied Materials and Optoelectronic Engineering, began his academic journey in the field of electrical engineering before delving into photonics and nanomaterials. His alma mater, National Taiwan University’s fiercely competitive Department of Electrical Engineering, has been the top choice for Taiwanese students taking the university entrance exam for the past decades.

After rigorous training through NTU's undergraduate and graduate programs from 1991 to 1997, Chen left Taipei to pursue a doctoral degree at the University of California, Irvine from 2005 to 2008. It was here, in a dimly lighted campus laboratory, that he first caught a glimpse of the imperfections within the GaN transistors of that era. He proceeded to dedicate his thesis to this discovery, and graduated with both a Ph. D. degree and a book offer from a German publisher.

“At that time, researching GaN transistors was a new field,” the distinguished professor explains. “These high-power transistors are used in cellular towers, satellites, and even in outer space, but [the design then] lacked stability and contained structural flaws that could be rectified by optoelectronics.”

The materials used in his doctoral studies were procured from an American arms manufacturer that crafted F51 fighter jets and is now known as Northrop Grumman, a global aerospace and defense technology company. Unable to secure a source for such transistors upon returning to Taiwan, Chen turned his attention to the more readily available zinc oxide (ZnO) nanoparticles.

Described by the professor as “structurally identical” to the hexagonal columnar basalt found on Taiwan's Penghu Islands, crystalized ZnO particles are actually a million times larger in terms of mass. This stretch of surface is extremely advantageous in making light, portable nano-sensors that can be used to reliably measure carbon monoxide levels or ultraviolent rays.

Chen compares the process — that of introducing nanomaterials to zinc oxide to create completely new ZoN nanostructures — to “changing the toppings on a subway sandwich” to refine the properties of the end product differently each time.

Respected among his peers as a well-trained engineer who has never ceased his research efforts, Chen maintains a steady publishing average of 8 articles per year in international science master journals listed on the Science Citation Index (SCI).

This track record is matched by only a handful of NCNU faculty members, however Chen humbly redirects the compliment instead to acknowledge the collective hard work of the optoelectronics department’s instructors and student researchers.

He interjects: “There is a student who is working on those fresh perovskite [solar] cells, heard it was similar to Intel’s research.”

Chen took up the post of departmental chair last year upon completing a sabbatical and visiting at the research lab of Yale's acclaimed Professor of Technological Innovation Jung Han (韓仲). Apart from livening up his department’s recruitment and teaching process, he is also leading the way for more case studies, hands-on experiments, and industry knowledge such as the latest breakthroughs in technology and applications.

One of his recent lectures was on optical tweezers invented by the 2018 Nobel Prize in Physics team that grab atoms, molecules, and DNA with laser beam fingers; the lasers push small particles towards the center of the beam and hold them there.

The professor dutifully recites the tremendous employment opportunities that come with a bachelor's degree in the field: Taiwan Semiconductor Manufacturing Company (TSMC), United Microelectronics Corporation (UMC), Micron Technology, and Epistar. Other graduates opt for further studies at institutions such as Carnegie Mellon and Duke.

Two recent graduates are now serving as research engineers at TSMC, he says, drawing attention to the importance of deep familiarity with both the compositional and modular properties of semiconductors. “Having a background in manufacturing and sensor-testing semiconductors, as well as knowledge of the physics and materials used, will open up a lot of doors in both the electronics industry and the optoelectronics field.”

Academic-industry cooperation on a community level is another passion of Chen's, in which he seeks to deepen exchanges and partnerships with local LED firms and solar cell makers such as those based at Nantou's science park. “Local businesses are in need of highly skilled labor, graduates are in need of employment; we are here to create networks,” he explains.

In recent years, NCNU has been an avid participant in several programs supported by the Ministry of Education's Center for University Social Responsibility. These include cross-fertilizing Taiwan's agricultural powerhouse with optoelectronics, and now Nantou’s water bamboo and passion fruits are grown with the aid of LED lights.

Moreover, NCNU researchers are currently identifying the best wavelength, intensity, and duration for specific cultivars based on their innate growth cycle and biological characteristics.

How do a new generation of Taiwanese scholars prepare themselves for this field? To this, Chen replies with the 3 keystones of optoelectronics — light, display, and energy source.

NCNU's curriculum prides itself on providing in-depth understanding of the characteristics of the materials used, as well as the parameters for reading photonic and gaseous levels. This field is a gateway to electrical engineering, chemistry, physics, optoelectronics, and many more fascinating areas of study, so why not take the chance to learn more about semiconductors to broaden one's scientific knowledge and employability?

Professor Chen's rich scientific sensibilities have further cemented the credibility of NCNU's Department of Applied Materials and Optoelectronic Engineering. The reward for developing engaging research projects and experiment-based training? Exceeding recruitment expectations during the time of the coronavirus — full classrooms that the devoted Chen sees as a divine deliverance of grace.

Tags:  Chen Hsiang  Graphene  LED  nanomaterials  National Chi Nan University  optoelectronics  Semiconductors 

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First Graphene continues to validate PureGRAPH® Product Quality through National Physical Laboratory (NPL) collaboration

Posted By Graphene Council, Tuesday, September 8, 2020
The assurance of product quality and consistency is vital for the successful adoption of graphene additives by downstream customers. With a strong focus on product quality with its PureGRAPH® graphene product range, First Graphene has made significant progress in this area. Implementing state of the art analytical methods, participating in establishing international standards (ISO/TC229) and use of 6-sigma approaches to control manufacturing processes have all contributed to establishing PureGRAPH® as the leading brand for quality in the industry[i]. First Graphene continues to pursue improved methods for the characterisation of graphene products and has announced a new collaboration with the National Physical Laboratory (NPL), UK a globally acknowledged, independent laboratory.

World-leading measurement solutions are critical to business and government, accelerating research and innovation, improving quality of life and enabling trade. Following the COVID-19 crisis the NPL with the support of National Measurement Laboratory partners launched the Measurement for Recovery (M4R) programme[ii], to support UK companies. First Graphene has successfully secured a place on the programme to study the Specific Surface Area of PureGRAPH® products.

Specific Surface Area is an important parameter of graphene platelets, that may impact dispersion and polymer wetting, and a critical parameter for regulatory authorities to enable them to categorise new substances and compare toxicology and environmental fate profiles. Specific Surface Area of powders is typically characterised by the BET (Brunauer-Emmett-Teller) method which uses nitrogen gas adsorption to characterise the surface area. In recent work by NPL[iii], researchers investigated factors that impact upon BET measurements including the pristine nature of the graphene platelets.

In the collaborative M4R project, NPL researchers will determine the BET specific surface area of a range of PureGRAPH® products and intermediates, to determine the factors that affect the results of BET measurements.  The project is currently underway.

Paul Ladislaus, CTO of First Graphene says, “This study will provide further understanding of the surface area of our products, enabling us to provide world-class information to our customers and regulatory authorities.”

Keith Paton, Senior Research Scientist at NPL says “The M4R programme supports projects with UK companies, such as First Graphene, to enable innovation through measurement and this study will provide important insights into how the BET method can be effectively deployed by the graphene industry.”

Tags:  additives  First Graphene  Graphene  Keith Paton  National Physical Laboratory  Paul Ladislaus 

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UH Announces Funding for Carbon Management Projects

Posted By Graphene Council, Tuesday, September 8, 2020
The Center for Carbon Management in Energy at the University of Houston has awarded $275,000 in research funding for projects focused on carbon management and the energy transition.

The projects cover a range of projects, from converting carbon to fuel and other useful products to a proposed new wireless monitoring system for carbon capture storage.

The Center for Carbon Management in Energy was launched as a University research center in 2019 to form an academic-industry consortium to reduce industry’s carbon footprint and find new business opportunities for carbon dioxide, methane and other greenhouse gas emissions.

Ramanan Krishnamoorti, chief energy officer at UH, said the first round of funding is intended to jumpstart solutions needed for Houston and the world to prosper in the energy transition.

“No one solution will be sufficient to achieve a low-carbon world,” he said. “We must be thinking about moving to low- and zero-carbon fuel sources while also addressing the challenges of capturing and utilizing the carbon we currently produce.”

The projects were drawn from 19 proposals and selected by a panel comprised of UH experts and industry representatives from Shell, Chevron, BP, Kiewit and Baker Hughes.  

Amr Elnashai, vice president for research and technology transfer at UH, said the center, and the transformational work it will be able to leverage, play an important role in the University’s goals to both increase research output by 50% in five years and to provide innovative solutions for societal concerns.

“The Center for Carbon Management in Energy is the focal point for our efforts to provide scalable solutions to industry and societal needs,” Elnashai said. “These research projects provide a sense of the wide range of work that the center will spur.”

The selected projects and principal investigators, all from UH, include:

• Carbon capture and storage in depleted gas fields along the Gulf of Mexico, Dimitrios G. Hatzignatiou, professor of petroleum engineering
• Single-step direct air capture and conversion to fuels and chemicals, Praveen Bollini, assistant professor of chemical and biomolecular engineering
• Converting carbon waste to graphite, graphene and morphed graphene for energy and structural applications, Francisco Robles Hernandez, associate professor of engineering technology
• All-day carbon capture and sequestration through molecular and phase-change hybrid modules, Hadi Ghasemi, Cullen Associate Professor of Mechanical Engineering
• Real-time subsurface wireless communication and sensing for CO2 storage, Jiefu Chen, assistant professor of electrical and computer engineering
• Processing algae to biodiesel and organic acid to enable microalgae-based carbon capture, Venkatesh Balan, assistant professor of engineering technology

Money for the grants was drawn primarily from industry contributions, said Charles McConnell, executive director for Carbon Management and Energy Sustainability at UH.

The projects, funded for 12 or 18 months, were selected based on technical merit and relevance to the marketplace, McConnell said, with the ultimate goal of spurring new partnerships to commercialize new carbon management technologies.

Tags:  Amr Elnashai  Charles McConnell  Energy Storage  Graphene  Ramanan Krishnamoorti  The Center for Carbon Management in Energy  University of Houston 

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UTC students enjoy first employer project of the year

Posted By Graphene Council, Tuesday, September 8, 2020
Our new year 10 and year 12 cohorts took part in their first employer project of the year. This gave our students a fantastic opportunity to demonstrate their creativity and problem solving skills on real life scenarios set by two of our main employer partners; CGI and Versarien.

Our digital technologies and cyber security students were tasked by CGI with designing a new computer game for younger children to help them develop their understanding of cyber security risks online.

Our engineering students were tasked by Versarien with researching Graphene and designing a use for a Graphene imbued 3D printed object.

We were really impressed with our new cohorts of students and are excited to see what they produce in the upcoming employer projects.

Tags:  3D printing  CGI GROUP  Graphene  SGS Berkeley Green UTC  Versarien 

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First 2D neural network

Posted By Graphene Council, Tuesday, September 8, 2020
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) in collaboration with Samsung Advanced Institute of Technology have developed the first neural network for artificial intelligence made using two-dimensional materials. Two-dimensional materials are substances with a thickness of a few nanometers or less, often consisting of a single sheet of atoms. This machine vision processor made from these materials can capture, store and recognize more than 1,000 images. 

“This work highlights an unprecedented advance in the functional complexity of 2D electronics,” said Donhee Ham, the Gordon McKay Professor of Electrical Engineering and Applied Physics at SEAS and senior author of the paper. “We have performed both front-end optical image sensing and back-end image recognition in one, 2D, material platform.”

This work highlights an unprecedented advance in the functional complexity of 2D electronics. DONHEE HAM, GORDON MCKAY PROFESSOR OF ELECTRICAL ENGINEERING AND APPLIED PHYSICS.

Since the discovery of graphene in 2004, researchers have been working to harness the unique electronic and optoelectronic properties of atomically thin, two-dimensional semiconductors for the basic building blocks of a range of applications. 

Transistors made from two-dimensional materials have been used for simple digital logic circuits and photodetectors but large-scale integration for complex computing, such as artificial intelligence, has remained out of reach. So far, researchers have only been able to integrate about 100 transistors made from two-dimensional materials onto a single chip.  To put that in perspective, standard silicon integrated circuits, such as those in your smartphone, contain billions of transistors. 

Now, Ham and his team have developed an integrated circuit with more than 1,000 two-dimensional material-based transistors.  

“Two-dimensional material-based devices exhibit various exciting properties, but low integration level has restricted their functional complexity,” said Houk Jang, a research associate at SEAS and first author of the paper. “With 1,000 devices integrated on a single chip, our atomically thin network can perform vision recognition tasks, which is a remarkably advanced functionality of two-dimensional material-based electronics.”

The research team used a two-dimensional material called molybdenum disulfide (MoS2), the three-atom thick semiconductor, which interacts well with light. They arranged these photosensitive transistors into what’s known as a crossbar array, which is inspired by neuronal connections in the human brain. This relatively simple set-up allows the device to act as both an eye that can see an image and a brain that can store and recognize an image. 

On the front end, the crossbar array acts like an image sensor, capturing an image just like an eye. The photosensitivity of the materials means that the image can be stored and converted into electrical data. On the back end, the same crossbar array can perform networked computing on that electrical data to recognize and identify the image.

To demonstrate the process, the researchers showed the device 1,000 images of handwritten digits. The processor was able to identify the images with 94 percent accuracy.

“Through capturing of optical images into electrical data like the eye and optic nerve, and subsequent recognition of this data like the brain via in-memory computing, our optoelectronic processor emulates the two core functions of human vision,” said Henry Hinton, a graduate student at SEAS and coauthor of the paper. 

“This is the first demonstration of a neural network with two-dimensional materials that can interact with light,” said Jang. “Because it computes in memory, you don’t need separate memory and the calculation can be done with very low energy.” 

Next, the team aims to scale up the device even further for two-dimensional material-based, high resolution imaging system.

Tags:  2D materials  Donhee Ham  Graphene  Harvard John A. Paulson School of Engineering  Samsung Advanced Institute of Technology  Sensors  transistors 

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Researchers Synthesize Ag2S/Reduced Graphene Oxide Composite Catalysts

Posted By Graphene Council, Tuesday, September 8, 2020
The development of efficient electrocatalyst to produce molecular hydrogen from water is receiving considerable attention, in an effort to decrease our reliance on fossil fuels. Silver sulfide (Ag2S) nanocrystals have attracted enormous interests due to its excellent properties.

At present, the performance of hydrogen generation reaction (HER) catalysts based on Ag2S nanocrystals are still at a certain distance from expectations. One of the main reasons is that the impeded charge transfer and decreased active sites caused by aggregation of Ag2S nanocrystals.

To solve this problem, a research team led by Prof. YU Weili from the Changchun Institute of Optics, Fine Mechanics, and Physics (CIOMP) of the Chinese Academy of Sciences and Prof. Hicham Idriss of King Abdullah University of Science and Technology (KAUST) synthesized Ag2S/rGO composite catalysts with smaller crystal size and better charge transfer properties by the solution fabrication strategy.

The study was published in Catalysts on August 19.

The researchers combined the high quality Ag2S nanocrystals with reduced graphene oxide with high carrier mobility, and prepared efficient HER catalysts. 

Compared to catalyst based on pure Ag2S nanocrystals, the Ag2S/rGO composites catalyst showed a significant decrease of overpotential, Tafel slope and electrochemical resistance. Transmission electron microscope (TEM) images showed that the induced rGO provided abundant nucleation sites, thus preventing the aggregation of Ag2S nanocrystals.

The average size of Ag2S nanocrystals grown on rGO was calculated to be about 7 nm.

Time-resolved photoluminescence (TRPL) studies showed that the improvement of the catalystic performance was mainly attributed to the efficient charge transfer of the Ag2S/rGO composites. 

In this study, Ag2S nanocrystals and two-dimensional material rGO are effectively combined to improve the catalytic performance through the synergistic advantages of the two materials in carrier transfer and aggregation inhibition. 

The study provides a new way for the preparation of high performance composite HER catalysts.

Tags:  and Physics  Changchun Institute of Optics  Fine Mechanics  Graphene  Graphene Oxide  Hicham Idriss  King Abdullah University of Science and Technology  YU Weili 

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