Category Archives: Flexible Displays

By Jeff Dorsch, Contributing Editor

Applied Materials on Wednesday reported that its proposed merger with Tokyo Electron Ltd. (TEL) is still under way, without giving a deadline or expected date of conclusion.

President and CEO Gary Dickerson said the company is “making progress with regulators” and plans to “complete the merger as soon as possible.” He declined to elaborate on that point, on advice of its attorneys.

Applied and TEL teams are working together to fulfill “the strategic opportunity this merger creates,” Dickerson said.

For the fiscal first quarter ended January 25, Applied received orders of $2.27 billion, up 1 percent from the fourth fiscal quarter and down 1 percent from a year earlier. The company posted sales of $2.36 billion, an increase of 4 percent from Q4 and up 8 percent from a year ago. Net income was $338 million, up 21 percent from the previous year’s $279 million.

“Major technology inflections in semiconductor and display are creating new growth opportunities for Applied`s precision materials engineering products and services,” Dickerson said in a statement. “With focus and execution, we are gaining momentum toward our long-term strategic goals, and this progress will be accelerated by our planned merger with Tokyo Electron.”

Applied forecasts sales in the second fiscal quarter will be flat to up a couple of percentage points from Q1. Dickerson said memory chips will drive demand for equipment in the fiscal first half, and the second half will see growth from foundries placing orders for equipment to be used in producing devices with FinFETs.

The announcement by GTAT and Apple in late 2013 of a more than $1 billion combined investment to set up the largest sapphire crystal growth facility in the world had raised hopes that adoption of sapphire in smartphones would rapidly reach a massive scale, with Apple setting up the pace and forcing its competitor to follow suit. Various second tier cell phone OEM upped their efforts in sapphire-related developments and tried to beat Apple by announcing or introducing smartphone models with sapphire display covers ahead of the highly anticipated iPhone 6 announcement. This prompted various sapphire manufacturers in China to announce plans for significant capacity increases to serve this new market.

“After a 2014 year full of hopes, the sapphire industry is entering 2015 with a lots of uncertainties,” analyzes Dr Eric Virey, Senior, Technology & Market Analyst, Yole Développement (Yole). “Following a long period of depressed pricings and stagnating revenue, 2014 started with a welcome price recovery that lifted up the spirit of many industry players. But most of all, it was the prospect of a new killer application that had given reasons for optimism,” he adds.

But the news that the iPhone 6 would not use a sapphire display cover, shortly followed by GTAT bankruptcy sent shockwaves in the industry and raised many questions:

  • Is Apple still interested in sapphire and will the display cover glass opportunity ever materialize in a large scale?
  • Is the technology ready?
  • What will happen to the more than 2000 high capacity furnaces installed by GTAT and Apple?
  • Are other cell phone OEM still considering sapphire?
  • Can traditional applications such as LED or watch windows sustain more than 100 manufacturers?
  • Could other applications emerge soon? If not how will consolidation affect the industry?
  • Will China eventually dominate the sapphire industry?

GTAT and Apple

Yole analysts have been tracking the sapphire market for more than a decade. Their analysis is presented in the yearly technology & market analysis: Sapphire Applications & Market: from LED to Consumer Electronic and Sapphire Applications, Touch screens, displays, semiconductor, defense and consumer.

“The last 6 month events are shaking the sapphire industry,” comments Eric Virey from Yole. He adds: “Today, several points remain under questions: is the display cover application dead on arrival? What is Apple’s strategy regarding sapphire? Can the market absorb the more than 2000 high capacity GTAT furnaces now for sale.”

Under this context, Yole, the “More Than Moore” market research, technology and strategy consulting company, proposes to exchange and debate during the 1st International Forum on Sapphire Market & Technologies, on September 3rd, 2015. This Forum is hosted by CIOE. It will take place in Shenzhen, alongside the 17th China International Optoelectronic Expo 2015.

Both partners have set up a high added-value program including sessions on: sapphire market, technologies and supply chain – established and emerging sapphire applications – crystal growth – manufacturing technologies… The forum will wrap up with a round table with leading industry players and experts to discuss the future of sapphire technologies and markets.

“This 1st International Forum on Sapphire Market & Technologies is a must for all sapphire industry managers as well as for sapphire users in order to network and learn about all the latest industry trends,” comments Eric Virey.

The Yole & CIOE sapphire forum will bring together a world class panel of experts. It will allow participants to get valuable insights into the status and future of the sapphire industry. Moreover, the Forum will provide unprecedented opportunities for meetings with industry leaders.

Gov. Charlie Baker today announced a $4 million dollar grant from the Massachusetts Technology Collaborative (“MassTech”) to UMass Lowell to support development of a printed and flexible electronics industry cluster, an emerging field that has the potential to become a $76 billion global market in the next decade.

The new Printed Electronics Research Collaborative (PERC) at UMass Lowell intends to position Massachusetts employers, large and small, to capitalize on the burgeoning printed and flexible electronics field, whether through direct development of products or as a piece of the supply chain. The PERC will initially focus on supporting the state’s defense cluster in printed electronics, but long-term, these technologies are expected to also have a broad range of applications in fields including health care, telecommunications and renewable energy. Printable electronics is currently a $16 billion global market and is projected to quadruple in 10 years, according to a 2014 report by IDTechEx.

“It is a privilege to announce today’s grant as another positive step forward for UMass Lowell, students and businesses across the Commonwealth. We have already seen great success stem from this partnership to fund research, support education and make new strides in innovation,” said Gov. Baker. “By connecting the incredible resources in our universities with the business community, the Commonwealth will continue to stimulate economic growth and create more good-paying jobs.”

The four-year grant award will be matched by $12 million in industry support and is being made as part of the Collaborative Research and Development Matching Grant Program, a $50 million dollar capital fund formed to support large-scale, long-term research projects that have high potential to spur innovation, cluster development and job growth in the Commonwealth. The fund was created as part of the 2012 Jobs Bill and is managed by the Innovation Institute at MassTech. Proposals are reviewed by an Investment Advisory Committee composed of executives from academia, industry, and the venture capital communities.

UMass Lowell Chancellor Marty Meehan and MassTech CEO Pamela Goldberg joined Gov. Baker at UMass Lowell’s Mark and Elisia Saab Emerging Technologies and Innovation Center, an 84,000-square-foot, state-of-the-art research facility where PERC will connect businesses with the expertise of UMass Lowell researchers. The MassTech grant will outfit laboratories and other research space at the Saab Center, also home to the Raytheon-UMass Lowell Research Institute, which will be among the participants in PERC. Other companies that have signed on include MicroChem of Westborough, Rogers Corp. of Burlington, SI2 Technologies of Billerica and Triton Systems of Chelmsford and more are expected, according to UMass Lowell Vice Provost for Research Julie Chen.

“Our mission is to convene industry, academia and government to catalyze economic opportunity in regions and clusters around the Commonwealth,” said Pamela Goldberg, CEO of the Massachusetts Technology Collaborative. “This project hits the mark on several fronts, including the potential to drive the development of innovative products and business growth. We are excited to partner with UMass Lowell and regional industry partners like Raytheon to expand R&D capacity and help advance this exciting new industry cluster.”

“UMass Lowell has decades of experience in partnering with businesses, large and small, to advance technologies and economic development. Not only does bringing our researchers together with innovators in industry stimulate economic growth, it offers our students unparalleled opportunities for experiential education,” Meehan told attendees, including representatives of the business and technology communities, UMass Lowell and the Lowell legislative delegation. “We are grateful to the Commonwealth for its investment in what we believe will be a model for academic and industry collaboration.”

Highlighting the importance of both public and private investment in the University of Massachusetts, today’s event also included the announcement by UMass Lowell that two of its most successful and generous alumni are making another multimillion-dollar gift to the campus and students, bringing their total commitment to the campus to nearly $10 million.

Robert and Donna Manning, Methuen natives who earned degrees at UMass Lowell, will commit an additional $4 million to the university to be used specifically for strategic initiatives in UMass Lowell’s Robert J. Manning School of Business and the School of Nursing.

The gift, combined with the MassTech grant, will strengthen the university’s North Campus Innovation District, located on University Avenue in Lowell. Made up of the Saab Center, the Manning School, the Lydon Library and nearby academic and laboratory complex, the district brings together the expertise of UMass Lowell’s engineering, science and business programs to provide ease of access for students, entrepreneurs and industry partners.

The business school was named for Rob Manning in May 2011 in recognition of the couple’s earlier multimillion-dollar commitment to the university. Since the Mannings graduated from UMass Lowell in the 1980s, they have supported capital and other initiatives at the university, including establishing the Robert and Donna Manning Endowment Fund, which supports scholarships for students majoring in nursing and business. Rob Manning began his career at MFS Investment Management shortly after receiving his UMass Lowell degree in business administration. He worked his way up from research analyst to chairman, a role he has held since 2010, overseeing billions of dollars in assets and employees in 80 countries around the world.  Donna Manning – whose career as an oncology nurse at a Boston hospital spans three decades – earned degrees in nursing and business administration at UMass Lowell.

“Donna and I received a world-class education at UMass Lowell that allowed us to become successful in our careers and our passion is to give back to future generations so they can fulfill their hopes and dreams,” said Rob Manning.

The latest commitment to UMass Lowell by the Mannings will support strategic priorities in the university’s School of Nursing and the Manning School of Business. Those include providing resources for the new dean of the business school as its new home, the Pulichino Tong Business Building, is constructed and outfitted, as well as equipping the new nursing simulation laboratory in the Health and Social Sciences Building.

“Once again, UMass Lowell is grateful to Rob and Donna Manning for their generosity and their support for the future of business and nursing education on our campus. They understand firsthand how a UMass Lowell education positions students for success after graduation and thanks to their gift, our students will be even more prepared they enter the job market,” said Meehan.

With its high electrical conductivity and optical transparency, indium tin oxide is one of the most widely used materials for touchscreens, plasma displays, and flexible electronics. But its rapidly escalating price has forced the electronics industry to search for other alternatives.

One potential and more cost-effective alternative is a film made with silver nanowires–wires so extremely thin that they are one-dimensional–embedded in flexible polymers. Like indium tin oxide, this material is transparent and conductive. But development has stalled because scientists lack a fundamental understanding of its mechanical properties.

Now Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at Northwestern University’s McCormick School of Engineering, has led research that expands the understanding of silver nanowires’ behavior in electronics.

Espinosa and his team investigated the material’s cyclic loading, which is an important part of fatigue analysis because it shows how the material reacts to fluctuating loads of stress.

“Cyclic loading is an important material behavior that must be investigated for realizing the potential applications of using silver nanowires in electronics,” Espinosa said. “Knowledge of such behavior allows designers to understand how these conductive films fail and how to improve their durability.”

By varying the tension on silver nanowires thinner than 120 nanometers and monitoring their deformation with electron microscopy, the research team characterized the cyclic mechanical behavior. They found that permanent deformation was partially recoverable in the studied nanowires, meaning that some of the material’s defects actually self-healed and disappeared upon cyclic loading. These results indicate that silver nanowires could potentially withstand strong cyclic loads for long periods of time, which is a key attribute needed for flexible electronics.

“These silver nanowires show mechanical properties that are quite unexpected,” Espinosa said. “We had to develop new experimental techniques to be able to measure this novel material property.”

The findings were recently featured on the cover of the journal Nano Letters. Other Northwestern coauthors on the paper are Rodrigo Bernal, a recently graduated PhD student in Espinosa’s lab, and Jiaxing Huang, associate professor of materials science and engineering in McCormick.

“The next step is to understand how this recovery influences the behavior of these materials when they are flexed millions of times,” said Bernal, first author of the paper.

University of Wisconsin-Madison materials engineers have made a significant leap toward creating higher-performance electronics with improved battery life — and the ability to flex and stretch.

Led by materials science Associate Professor Michael Arnold and Professor Padma Gopalan, the team has reported the highest-performing carbon nanotube transistors ever demonstrated. In addition to paving the way for improved consumer electronics, this technology could also have specific uses in industrial and military applications.

In a paper published recently in the journal ACS Nano, Arnold, Gopalan and their students reported transistors with an on-off ratio that’s 1,000 times better and a conductance that’s 100 times better than previous state-of-the-art carbon nanotube transistors.

“Carbon nanotubes are very strong and very flexible, so they could also be used to make flexible displays and electronics that can stretch and bend, allowing you to integrate electronics into new places like clothing,” says Arnold. “The advance enables new types of electronics that aren’t possible with the more brittle materials manufacturers are currently using.”

Carbon nanotubes are single atomic sheets of carbon rolled up into a tube. As some of the best electrical conductors ever discovered, carbon nanotubes have long been recognized as a promising material for next-generation transistors, which are semiconductor devices that can act like an on-off switch for current or amplify current. This forms the foundation of an electronic device.

However, researchers have struggled to isolate purely semiconducting carbon nanotubes, which are crucial, because metallic nanotube impurities act like copper wires and “short” the device. Researchers have also struggled to control the placement and alignment of nanotubes. Until now, these two challenges have limited the development of high-performance carbon nanotube transistors.

Building on more than two decades of carbon nanotube research in the field, the UW-Madison team drew on cutting-edge technologies that use polymers to selectively sort out the semiconducting nanotubes, achieving a solution of ultra-high-purity semiconducting carbon nanotubes.

Previous techniques to align the nanotubes resulted in less-than-desirable packing density, or how close the nanotubes are to one another when they are assembled in a film. However, the UW-Madison researchers pioneered a new technique, called floating evaporative self-assembly, or FESA, which they described earlier in 2014 in the ACS journal Langmuir. In that technique, researchers exploited a self-assembly phenomenon triggered by rapidly evaporating a carbon nanotube solution.

The team’s most recent advance also brings the field closer to realizing carbon nanotube transistors as a feasible replacement for silicon transistors in computer chips and in high-frequency communication devices, which are rapidly approaching their physical scaling and performance limits.

“This is not an incremental improvement in performance,” Arnold says. “With these results, we’ve really made a leap in carbon nanotube transistors. Our carbon nanotube transistors are an order of magnitude better in conductance than the best thin film transistor technologies currently being used commercially while still switching on and off like a transistor is supposed to function.”

The researchers have patented their technology through the Wisconsin Alumni Research Foundation and have begun working with companies to accelerate the technology transfer to industry.

The Internet of Everything, cloud computing/big data and 3-D printing are the three technologies most likely to transform the world during the next five years, according to IHS Technology.

“We know that technology has the capability to change the world: from the Gutenberg printing press to the steam engine to the microchip,” said Ian Weightman, vice president, research & operations, IHS Technology. “But how can we determine which technologies are likely to have the greatest potential to transform the future of the human race? What is the process to distinguish among the innovations that will have limited impact and those that will be remembered as milestones on the path of progress? How can you tell the difference between the VHS and Betamax of tomorrow’s technologies?”

“To answer these questions, IHS Technology gathered its leading experts representing the technology supply chain from electronic components to finished products across applications markets ranging from consumer, media, and telecom; to industrial, medical, and power. These experts were asked to nominate and vote for their top 10 most impactful technologies over the next five years.”

The top three technologies were: 3-D printing in third place; cloud computing/big data at No. 2; and the Internet of Everything coming out on top.

Manufacturing moves to next dimension with 3-D printing

Also called additive manufacturing, 3-D printing encourages design innovation by facilitating the creation of new structures and shapes, and allows limitless product complexity without additional production costs. It also greatly speeds up time to market by making the idea-to-prototype cycle much shorter.

Total revenue for the 3-D printing industry is forecast to grow by nearly 40 percent annually through 2020, when the aggregated market size is expected to exceed $35.0 billion, up from $5.6 billion in 2014.

Cloud computing/big data brings metamorphosis to computing and consumer markets

The cloud has become a ubiquitous description for on-demand provisioning of data, storage, computing power and services that are touching nearly every consumer and enterprise across the globe. Together with data analytics and mobile broadband, the cloud and big data are poised to reshape almost every facet of the consumer digital lifestyle experience and dramatically impact enterprise information technology (IT) strategies, while creating new opportunities and challenges for the various nodes in the entire information, communications and technology (ICT) value chain.

The cloud is transformational in the business landscape, changing the way enterprises interact with their suppliers, customers and developers.

The big data and data analytics segment is a separate but related transformational technology that harnesses the power of the cloud to analyze data for disparate sources to uncover hidden patterns, enable predictive analysis and achieve huge efficiencies in performance.

IHS forecasts that global enterprise IT spending on cloud-based architectures will double to approximately $230 billion in 2017, up from about $115 billion in 2012.

The Internet of Things becomes the Internet of Everything

The world is in the early stages of the Internet of Things (IoT)—a technological evolution that is based on the way that Internet-connected devices can be used to enhance communication, automate complex industrial processes and generate a wealth of information. To provide some context on the magnitude of this evolution, more than 80 billion Internet-connected devices are projected to be in use in 2024, up from less than 20 billion in 2014, as presented in the attached figure.

While the IoT concept is still relatively new, it is already transforming into a broader model: the Internet of Everything (IoE). The metamorphosis covers not just the number of devices but envisages a complete departure from the way these devices have used the Internet in the past.

Most of the connected devices in place today largely require direct human interaction and are used for the consumption of content and entertainment. The majority of the more than 80 billion future connections will be employed to monitor and control systems, machines and objects—including lights, thermostats, window locks and under-the-hood automotive electronics.

Other transformative technologies identified by IHS Technology analysts were:

  • Artificial intelligence
  • Biometrics
  • Flexible displays
  • Sensors
  • Advanced user interfaces
  • Graphene
  • Energy storage and advanced battery technologies

2015-01-12_Connectable_Devices

North American quantum dot manufacturer Quantum Materials Corp today announced it is increasing production capacity to 2000 kilograms (2 metric tons) of quantum dots and nanoparticles per annum in Q2 2015. The Company is able to leverage short development timelines to plan for increasing quantum dot production and anticipates further production expansion during the remainder of 2015.

“We have achieved quality, uniformity and scalability goals with our patented continuous-flow manufacturing process,” said Quantum Materials Corp CEO Stephen Squires, “and so are making the investments in production capacity and people to meet market demand for high-quality quantum dots. We have also made great strides in ramping-up volume production of both Cadmium-core and Cadmium-free (aka heavy-metal free) quantum dots. We perceive Cadmium-free quantum dots will drive future use, particularly in electronic goods destined for highly environmentally-regulated regions such as the European Union.”

The company has made significant capital investment in new automated nanoreactors, expanded lab space and scientific staffing to fulfill quality and quantity requirements for quantum dots in consumer electronics applications. Quantum Materials’ patented continuous-flow process produces quantum dots in the high volumes, uniformity and reliability needed for integration into UHD 4K LCD display, solid-state lighting, solar and biotech manufacturing industries. Up to this point, competitors’ batch synthesis methods have inhibited quantum dot-use in consumer electronics due to the limitations of a highly manual process in controlling quantum yield, color purity, volume production and the resultant higher production costs.

The company also released today an informative video detailing heavy–metal free quantum dot use and benefits in LCD display manufacturing.

Quantum Materials is at the forefront of Cadmium-free quantum dot development to allow manufacturers to meet and stay ahead of future environmental regulations governing dangerous materials in consumer electronic devices. Quantum dots are easily integrated into the industry-standard thin-film roll-to-roll inkjet and surface deposition technologies currently used in existing LCD display production lines and other next-generation printed electronics.

Quantum Materials executives CEO Stephen Squires and Senior Director of Business Development for Asia and the Pacific Toshi Ando are meeting with major LCD manufacturers at the 2015 International Consumer Electronics Show (CES). They will be participating in the Distributed Computing Industry Association’s (DCIA) “Internet of Things (IoT) Marathon” webcast.

Global shipments of diagnostic displays are forecast to grow at a 5 percent compound annual growth rate (CAGR), between 2014 and 2018. According to the latest DisplaySearch Specialty Displays Report, larger high-resolution wide-aspect-ratio displays are starting to become more popular, but 21.3-inch displays had a 67 percent share of unit shipments and a 65 percent share of revenues in the first half of 2014.

“The majority of future shipment growth will take place in emerging regions, not in developed regions, where much of the growth has previously occurred,” said Todd Fender, senior analyst professional and commercial displays for DisplaySearch, now part of IHS Inc. (NYSE: IHS). “At the county level, brands are looking to China, as the largest opportunity of growth, followed closely by Latin America.“

Fig. 1

Veteran radiologists who were trained on, and had previously read, images on traditional x-ray film using light boxes have been the driving force behind the continued strength of 21.3-inch displays with a 4:3 aspect ratio; however, as younger doctors enter the workforce, the legacy of film and grayscale-only images will slowly fade away. For example, in the first half of 2014, 43 percent of diagnostic displays were grayscale, but by 2018 these displays will represent just 34 percent of the market.

In today’s traditional picture archiving and communication (PACS) display ecosystem, multiple displays are used to review and read images; however, this configuration may lead to lower productivity and faster eye fatigue. Larger and higher resolution single screens have entered the market over the last few years, in an attempt to reduce or eliminate these issues. Displays with 6 megapixels (MP) to 10 (and higher) MPs are forecast to increase over the next several years, as users migrate from multiple screens to single-screen viewing.

Table 1

Clinical Review Displays and Surgical Displays

Similar to diagnostic shipments, clinical-review-display shipments are forecast to grow at a CAGR of 4 percent, between 2014 and 2018.  More than eight in 10 (83 percent) of clinical review display sizes fall between 19 inches and 22 inches, and 98 percent have a resolution of 2 MP or lower. “There will be a gradual shift to 4 MP and 8 MP wide aspect ratio displays as availability increases and as prices fall,” Fender said.

Surgical display shipments are forecast to grow more than any other medical-imaging category, reaching 7 percent CAGR between 2014 and 2018. Although almost half of surgical displays fall between 15 inches and 20 inches, the fastest area of growth is forecast to be in displays that 55 inches and larger, which are expected to grow at a 23 percent CAGR between 2014 and 2018. Additionally, 8 megapixel and 9 megapixel displays will grow significantly between 2014 and 2018; however, neither resolution will make up a large portion of the surgical display market.

“Larger displays are becoming more affordable, and they are being installed in surgical rooms as medical on-site and virtual professional collaboration becomes more popular,” Fender said. “Larger screens are much easier for multiple viewers, and many are also used as live teaching devices.”

LCD TV makers are responding to the challenge of OLED, with quantum dot (QD) technology, curved screens and other innovations. According to new information from DisplaySearch, now part of IHS Inc. (NYSE: IHS), in order to boost consumer value in the LCD television market, 4K ultra-high-definition (UHD) enhanced-color LCD TVs, using quantum dot (QD) technology will become available in 2015, with 1.3 million shipping worldwide. Shipments of quantum dot TVs are expected to grow to 18.7 million in 2018.

“While LCD technology undisputedly dominates the TV scene, manufacturers continue to innovate, in order to bring additional value to consumers,” said Paul Gray, director of European research at DisplaySearch. “The launch of new 4K UHD services promises to foment another round of innovation, as content creators bring richer, deeper colors to their art. Curved screens are also a popular feature this year, but there will be limited opportunity for growth, as the market for this feature is expected to peak next year.”

Based on information in the DisplaySearch Quarterly TV Design and Features Report, ITU-R Recommendation BT.2020 (rec.2020) colors promise a new level of fidelity that beyond the range of current high-definition TVs. “While broadcasters and cinematographers have begun to capture such images, the television industry has just started to respond to the challenge,” Gray said.

Fig 1

“Quantum dot is one of the weapons that the LCD industry is using to create ever more faithful images, which are very close to the full viewable range of the human eye,” Gray said. “Broadcasters are finalizing their plans for UHD, but they very clearly want there to be more to their UHD services than simply extra pixels. Richer colors work on any screen size, regardless of one’s visual acuity, and subtle shading increases the perception of reality. Quantum dot is part of the LCD industry’s response to the challenge posed by OLED technology and its use demonstrates that there is still room for innovation.”

Curved LCD TVs

A similar response to the challenge posed by OLED can be seen in the emergence of curved LCD TVs, which proves that LCD has further opportunities for innovation. In fact 1.8 million curved TVs are expected to ship in 2014, peaking at 8.2 million in 2016 and 2017. DisplaySearch analysts anticipate that Western Europe will be the dominant region for curved TVs, with 2.6 million shipping in both 2016 and 2017, resulting from consumer taste for unique design and Samsung’s dominant market share.

“Curved TVs are an industry styling fashion, in the same way that sets became very thin when the first LED backlights were introduced,” Gray said. “In due course, such fashions can burn through, leaving enduring value. For example, the legacy of thin TVs is their lower power consumption. It is easy to dismiss fashion, but it remains a critical element in maintaining value and consumer interest in the TV category.”

Fig 2

The Quarterly TV Design and Features Report tracks all 4K UHD TV product ranges, forecasts, video processing and broadcasting; plus, detailed information on other aspects of TV design such as smart TV, backlighting technology, OLED and 3D. This report is delivered in PowerPoint and includes Excel-based data and tables.

Physicists at the University of Kansas have fabricated an innovative substance from two different atomic sheets that interlock much like Lego toy bricks. The researchers said the new material — made of a layer of graphene and a layer of tungsten disulfide — could be used in solar cells and flexible electronics. Their findings are published today by Nature Communications.

Hsin-Ying Chiu, assistant professor of physics and astronomy, and graduate student Matt Bellus fabricated the new material using “layer-by-layer assembly” as a versatile bottom-up nanofabrication technique. Then, Jiaqi He, a visiting student from China, and Nardeep Kumar, a graduate student who now has moved to Intel Corp., investigated how electrons move between the two layers through ultrafast laser spectroscopy in KU’s Ultrafast Laser Lab, supervised by Hui Zhao, associate professor of physics and astronomy.

 “To build artificial materials with synergistic functionality has been a long journey of discovery,” Chiu said. “A new class of materials, made of the layered materials, has attracted extensive attention ever since the rapid development of graphene technology. One of the most promising aspects of this research is the potential to devise next-generation materials via atomic layer-level control over its electronic structure.”

According to the researchers, the approach is to design synergistic materials by combining two single-atom thick sheets, for example, acting as a photovoltaic cell as well as a light-emitting diode, converting energy between electricity and radiation. However, combining layers of atomically thin material is a thorny task that has flummoxed researchers for years.

“A big challenge of this approach is that, most materials don’t connect together because of their different atomic arrangements at the interface — the arrangement of the atoms cannot follow the two different sets of rules at the same time,” Chiu said. “This is like playing with Legos of different sizes made by different manufacturers. As a consequence, new materials can only be made from materials with very similar atomic arrangements, which often have similar properties, too. Even then, arrangement of atoms at the interface is irregular, which often results in poor qualities.”

Layered materials such as those developed by the KU researchers provide a solution for this problem. Unlike conventional materials formed by atoms that are strongly bound in all directions, the new material features two layers where each atomic sheet is composed of atoms bound strongly with their neighbors — but the two atomic sheets are themselves only weakly linked to each other by the so-called van der Waals force, the same attractive phenomenon between molecules that allows geckos to stick to walls and ceilings.

“There exist about 100 different types of layered crystals — graphite is a well-known example,” Bellus said. “Because of the weak interlayer connection, one can choose any two types of atomic sheets and put one on top of the other without any problem. It’s like playing Legos with a flat bottom. There is no restriction. This approach can potentially product a large number of new materials with combined novel properties and transform the material science.”

Chiu and Bellus created the new carbon and tungsten disulfide material with the aim of developing novel materials for efficient solar cells. The single sheet of carbon atoms, known as graphene, excels at moving electrons around, while a single-layer of tungsten disulfide atoms is good at absorbing sunlight and converting it to electricity. By combining the two, this innovative material can potentially perform both tasks well.

The team used scotch tape to lift a single layer of tungsten disulfide atoms from a crystal and apply it to a silicon substrate. Next, they used the same procedure to remove a single layer of carbon atoms from a graphite crystal. With a microscope, they precisely laid the graphene on top of the tungsten disulfide layer. To remove any glue between the two atomic layers that are unintentionally introduced during the process, the material was heated at about 500 degrees Fahrenheit for a half-hour. This allowed the force between the two layers to squeeze out the glue, resulting in a sample of two atomically thin layers with a clean interface.

Doctoral students He and Kumar tested the new material in KU’s Ultrafast Laser Lab. The researchers used a laser pulse to excite the tungsten disulfide layer.

“We found that nearly 100 percent of the electrons that absorbed the energy from the laser pulse move from tungsten disulfide to graphene within one picosecond, or one-millionth of one-millionth second,” Zhao said. “This proves that the new material indeed combines the good properties of each component layer.”

The research groups led by Chiu and Zhao are trying to apply this Lego approach to other materials. For example, by combining two materials that absorb light of different colors, they can make materials that react to diverse parts of the solar spectrum.

The National Science Foundation funded this work.