Yearly Archives: 2017

Fibers made of carbon nanotubes configured as wireless antennas can be as good as copper antennas but 20 times lighter, according to Rice University researchers. The antennas may offer practical advantages for aerospace applications and wearable electronics where weight and flexibility are factors.

The research appears in Applied Physics Letters.

The discovery offers more potential applications for the strong, lightweight nanotube fibers developed by the Rice lab of chemist and chemical engineer Matteo Pasquali. The lab introduced the first practical method for making high-conductivity carbon nanotube fibers in 2013 and has since tested them for use as brain implants and in heart surgeries, among other applications.

The research could help engineers who seek to streamline materials for airplanes and spacecraft where weight equals cost. Increased interest in wearables like wrist-worn health monitors and clothing with embedded electronics could benefit from strong, flexible and conductive fiber antennas that send and receive signals, Pasquali said.

The Rice team and colleagues at the National Institute of Standards and Technology (NIST) developed a metric they called “specific radiation efficiency” to judge how well nanotube fibers radiated signals at the common wireless communication frequencies of 1 and 2.4 gigahertz and compared their results with standard copper antennas. They made thread comprising from eight to 128 fibers that are about as thin as a human hair and cut to the same length to test on a custom rig that made straightforward comparisons with copper practical.

“Antennas typically have a specific shape, and you have to design them very carefully,” said Rice graduate student Amram Bengio, the paper’s lead author. “Once they’re in that shape, you want them to stay that way. So one of the first experimental challenges was getting our flexible material to stay put.”

Contrary to earlier results by other labs (which used different carbon nanotube fiber sources), the Rice researchers found the fiber antennas matched copper for radiation efficiency at the same frequencies and diameters. Their results support theories that predicted the performance of nanotube antennas would scale with the density and conductivity of the fiber.

“Not only did we find that we got the same performance as copper for the same diameter and cross-sectional area, but once we took the weight into account, we found we’re basically doing this for 1/20th the weight of copper wire,” Bengio said.

“Applications for this material are a big selling point, but from a scientific perspective, at these frequencies carbon nanotube macro-materials behave like a typical conductor,” he said. Even fibers considered “moderately conductive” showed superior performance, he said. Although manufacturers could simply use thinner copper wires instead of the 30-gauge wires they currently use, those wires would be very fragile and difficult to handle, Pasquali said.

“Amram showed that if you do three things right — make the right fibers, fabricate the antenna correctly and design the antenna according to telecommunication protocols — then you get antennas that work fine,” he said. “As you go to very thin antennas at high frequencies, you get less of a disadvantage compared with copper because copper becomes difficult to handle at thin gauges, whereas nanotubes, with their textile-like behavior, hold up pretty well.”

The 2017 GLOBALFOUNDRIES Technology Conference (GTC) was held today in Shanghai, with GF executives, customers, partners and leaders in the Chinese semiconductor industry gathering to discuss the technologies that will enable a new era of connected intelligence. At the event, GF senior executives shed light on the company’s technologies, design solutions, and manufacturing services. The company also highlighted growing momentum around its differentiated 22FDX® technology, including customer adoption by several leading Chinese chip designers.

Mike Cadigan, GF’s senior vice president for global sales and business development, delivered a keynote speech, emphasizing GF’s expectations to become a strong leader in the Chinese semiconductor market. “Along with the rapid growth of customers, markets and applications in this region of the world, we are also continuously developing new technologies for enabling connected intelligence,” Cadigan said. “China is definitely one of our most important markets, and we will keep bringing advanced and differentiated technologies here to help our customers grow and succeed.”

At the event, GF revealed three Chinese customers that will be adopting its new 22FDX technology for next-generation wireless, battery-powered applications. Shanghai Fudan Microelectronics Group will adopt the 22FDX platform to design and develop highly reliable servers, AI and smart IoT intelligent products in 2018. Rockchip will apply 22FDX technology in the design of ultra-low power WiFi smart hardware SoC and high-performance AI processers. Hunan Goke Microelectronics is planning to adopt 22FDX in its next generation of IoT chips.

China is a key region for GF’s future growth plans. The company is building an advanced 300mm semiconductor fab in Chengdu, where a “truss-hoisting” ceremony was recently held to commemorate a major milestone in the construction of the facility, which will be called Fab 11. The construction of the fab is progressing at a fast pace and is on track to be completed in early 2018.

The company is also working closely with the Chengdu municipality to expand the FD-SOI ecosystem, with an investment of more than $100 million to make Chengdu a center of excellence for FDX IC design and IP development. Several leading semiconductor companies have already committed to supporting the ecosystem initiative, including Invecas, GF’s advanced IP development partner. Invecas has established a strong presence in China, including a recently expanded engineering team in Shanghai and Shenzhen and a commitment to set up an R&D center in Chengdu to develop and support advanced IP and designs for FD-SOI systems.

The huge increase in computing performance in recent decades has been achieved by squeezing ever more transistors into a tighter space on microchips.

However, this downsizing has also meant packing the wiring within microprocessors ever more tightly together, leading to effects such as signal leakage between components, which can slow down communication between different parts of the chip. This delay, known as the “interconnect bottleneck,” is becoming an increasing problem in high-speed computing systems.

One way to tackle the interconnect bottleneck is to use light rather than wires to communicate between different parts of a microchip. This is no easy task, however, as silicon, the material used to build chips, does not emit light easily, according to Pablo Jarillo-Herrero, an associate professor of physics at MIT.

Now, in a paper published today in the journal Nature Nanotechnology, researchers describe a light emitter and detector that can be integrated into silicon CMOS chips. The paper’s first author is MIT postdoc Ya-Qing Bie, who is joined by Jarillo-Herrero and an interdisciplinary team including Dirk Englund, an associate professor of electrical engineering and computer science at MIT.

The device is built from a semiconductor material called molybdenum ditelluride. This ultrathin semiconductor belongs to an emerging group of materials known as two-dimensional transition-metal dichalcogenides.

Unlike conventional semiconductors, the material can be stacked on top of silicon wafers, Jarillo-Herrero says.

“Researchers have been trying to find materials that are compatible with silicon, in order to bring optoelectronics and optical communication on-chip, but so far this has proven very difficult,” Jarillo-Herrero says. “For example, gallium arsenide is very good for optics, but it cannot be grown on silicon very easily because the two semiconductors are incompatible.”

In contrast, the 2-D molybdenum ditelluride can be mechanically attached to any material, Jarillo-Herrero says.

Another difficulty with integrating other semiconductors with silicon is that the materials typically emit light in the visible range, but light at these wavelengths is simply absorbed by silicon.

Molybdenum ditelluride emits light in the infrared range, which is not absorbed by silicon, meaning it can be used for on-chip communication.

To use the material as a light emitter, the researchers first had to convert it into a P-N junction diode, a device in which one side, the P side, is positively charged, while the other, N side, is negatively charged.

In conventional semiconductors, this is typically done by introducing chemical impurities into the material. With the new class of 2-D materials, however, it can be done by simply applying a voltage across metallic gate electrodes placed side-by-side on top of the material.

“That is a significant breakthrough, because it means we do not need to introduce chemical impurities into the material [to create the diode]. We can do it electrically,” Jarillo-Herrero says.

Once the diode is produced, the researchers run a current through the device, causing it to emit light.

“So by using diodes made of molybdenum ditelluride, we are able to fabricate light-emitting diodes (LEDs) compatible with silicon chips,” Jarillo-Herrero says.

The device can also be switched to operate as a photodetector, by reversing the polarity of the voltage applied to the device. This causes it to stop conducting electricity until a light shines on it, when the current restarts.

In this way, the devices are able to both transmit and receive optical signals.

The device is a proof of concept, and a great deal of work still needs to be done before the technology can be developed into a commercial product, Jarillo-Herrero says.

The researchers are now investigating other materials that could be used for on-chip optical communication.

Most telecommunication systems, for example, operate using light with a wavelength of 1.3 or 1.5 micrometers, Jarillo-Herrero says.

However, molybdenum ditelluride emits light at 1.1 micrometers. This makes it suitable for use in the silicon chips found in computers, but unsuitable for telecommunications systems.

“It would be highly desirable if we could develop a similar material, which could emit and detect light at 1.3 or 1.5 micrometers in wavelength, where telecommunication through optical fiber operates,” he says.

To this end, the researchers are exploring another ultrathin material called black phosphorus, which can be tuned to emit light at different wavelengths by altering the number of layers used. They hope to develop devices with the necessary number of layers to allow them to emit light at the two wavelengths while remaining compatible with silicon.

“The hope is that if we are able to communicate on-chip via optical signals instead of electronic signals, we will be able to do so more quickly, and while consuming less power,” Jarillo-Herrero says.

Graphene – a one-atom-thick layer of the stuff in pencils – is a better conductor than copper and is very promising for electronic devices, but with one catch: Electrons that move through it can’t be stopped.

Until now, that is. Scientists at Rutgers University-New Brunswick have learned how to tame the unruly electrons in graphene, paving the way for the ultra-fast transport of electrons with low loss of energy in novel systems. Their study was published online in Nature Nanotechnology.

“This shows we can electrically control the electrons in graphene,” said Eva Y. Andrei, Board of Governors professor in Rutgers’ Department of Physics and Astronomy in the School of Arts and Sciences and the study’s senior author. “In the past, we couldn’t do it. This is the reason people thought that one could not make devices like transistors that require switching with graphene, because their electrons run wild.”

Now it may become possible to realize a graphene nano-scale transistor, Andrei said. Thus far, graphene electronics components include ultra-fast amplifiers, supercapacitors and ultra-low resistivity wires. The addition of a graphene transistor would be an important step towards an all-graphene electronics platform. Other graphene-based applications include ultra-sensitive chemical and biological sensors, filters for desalination and water purification. Graphene is also being developed in flat flexible screens, and paintable and printable electronic circuits.

Graphene is a nano-thin layer of the carbon-based graphite that pencils write with. It is far stronger than steel and a great conductor. But when electrons move through it, they do so in straight lines and their high velocity does not change. “If they hit a barrier, they can’t turn back, so they have to go through it,” Andrei said. “People have been looking at how to control or tame these electrons.”

Her team managed to tame these wild electrons by sending voltage through a high-tech microscope with an extremely sharp tip, also the size of one atom. They created what resembles an optical system by sending voltage through a scanning tunneling microscope, which offers 3-D views of surfaces at the atomic scale. The microscope’s sharp tip creates a force field that traps electrons in graphene or modifies their trajectories, similar to the effect a lens has on light rays. Electrons can easily be trapped and released, providing an efficient on-off switching mechanism, according to Andrei.

“You can trap electrons without making holes in the graphene,” she said. “If you change the voltage, you can release the electrons. So you can catch them and let them go at will.”

The next step would be to scale up by putting extremely thin wires, called nanowires, on top of graphene and controlling the electrons with voltages, she said.

An interdisciplinary team of scientists at the U.S. Naval Research Laboratory (NRL) has uncovered a direct link between sample quality and the degree of valley polarization in monolayer transition metal dichalcogenides (TMDs). In contrast with graphene, many monolayer TMDs are semiconductors and show promise for future applications in electronic and optoelectronic technologies.

In this sense, a ‘valley’ refers to the region in an electronic band structure where both electrons and holes are localized, and ‘valley polarization’ refers to the ratio of valley populations — an important metric applied in valleytronics research.

Upper Panel: schematic of optical excitation in the K valley of WS2 monolayers. Lower Panel: Photoluminescence (PL) intensity map of a triangular monolayer island of WS2 and the associated valley polarization map demonstrate the clear inverse relationship. Each map covers a 46 x 43 micron area. The regions exhibiting smallest PL intensity and lowest quality are found at the center of the flake and radiate outward toward the three corners. These regions correspond to the highest valley polarization. Credit: US Naval Research Laboratory

Upper Panel: schematic of optical excitation in the K valley of WS2 monolayers. Lower Panel: Photoluminescence (PL) intensity map of a triangular monolayer island of WS2 and the associated valley polarization map demonstrate the clear inverse relationship. Each map covers a 46 x 43 micron area. The regions exhibiting smallest PL intensity and lowest quality are found at the center of the flake and radiate outward toward the three corners. These regions correspond to the highest valley polarization. Credit: US Naval Research Laboratory

“A high degree of valley polarization has been theoretically predicted in TMDs yet experimental values are often low and vary widely,” said Kathleen McCreary, Ph.D., lead author of the study. “It is extremely important to determine the origin of these variations in order to further our basic understanding of TMDs as well as advance the field of valleytronics.”

Many of today’s technologies (i.e. solid state lighting, transistors in computer chips, and batteries in cell phones) rely simply on the charge of the electron and how it moves through the material. However, in certain materials such as the monolayer TMDs, electrons can be selectively placed into a chosen electronic valley using optical excitation.

“The development of TMD materials and hybrid 2D/3D heterostructures promises enhanced functionality relevant to future Department of Defense missions,” said Berend Jonker, Ph.D., principal investigator of the program. “These include ultra-low power electronics, non-volatile optical memory, and quantum computation applications in information processing and sensing.”

The growing fields of spintronics and valleytronics aim to use the spin or valley population, rather than only charge, to store information and perform logic operations. Progress in these developing fields has attracted the attention of industry leaders, and has already resulted in products such as magnetic random access memory that improve upon the existing charge-based technologies.

The team focused on TMD monolayers such as WS2 and WSe2, which have high optical responsivity, and found that samples exhibiting low photoluminescence (PL) intensity exhibited a high degree of valley polarization. These findings suggest a means to engineer valley polarization via controlled introduction of defects and nonradiative recombination sites

“Truly understanding the reason for sample-to-sample variation is the first step towards valleytronic control,” McCreary said. “In the near future, we may be able to accurately increase polarization by adding defect sites or reduce polarization by passivation of defects.”

Results of this research are reported in the August 2017 edition of the American Chemical Society’s Nano, The research team is comprised of Dr. Kathleen McCreary, Dr. Aubrey Hanbicki, and Dr. Berend Jonker from the NRL Materials Science and Technology Division; Dr. Marc Currie from the NRL Optical Sciences Division; and Dr. Hsun-Jen Chuang who holds an American Society for Engineering Education (ASEE) fellowship at NRL.

Leti, a research institute of CEA Tech, today announced a new European Horizon 2020 project to develop innovative electric drivetrains for third-generation electric vehicles.

Bringing together 10 European research institutes, key members of the automotive-industry value chain and universities, the ModulED project will focus on boosting drivetrain performance to meet vehicle-owner requirements, making manufacturing more efficient and reducing environmental impact and vehicle cost. The project team will leverage recent innovations from diverse industries. These include integrating the frequency, voltage and high-temperature benefits of wide-bandgap semiconductors fabricated with gallium nitride. These devices allow the electronic circuitry that changes direct current to alternating current (DC-AC) to be integrated directly into the motor.

Other recent innovations the project will develop for the new drivetrains include:

  • Processes for manufacturing magnetic materials for the magnetic part of the motor, lowering the density of the rare-earth element
  • Motor architecture that allows modularity in production
  • Transmission and cooling systems that are compatible with hybrid vehicles
  • Optimization of braking systems to recover energy in the braking phase.

“Electric vehicles are a key component of the EU’s commitment to limit climate change, but current electric vehicles face challenges preventing large market acceptance, including consumer resistance due to cost and limited driving ranges,” said Bernard Strée, project coordinator at Leti. “ModulED will target these challenges via the manufacturing process, including the mass-production context, increased value-chain involvement and lifecycle analysis for optimized duration and minimized environmental impact.”

Coordinated by Leti, the three-year, €7.2 million project includes the companies BRUSA Elektronik AG (Switzerland), Punch Powertrain NV (Belgium), ZG GmbH (Germany), Siemens (France), Efficient Innovation (France); universities RTWH Aachen University, Chalmers University and Eindhoven University of Technology, and Leti’s sister institute, Liten.

The ModulED project, which leverages Leti’s expertise in wide-bandgap semiconductors along with Liten’s knowhow in magnetic materials and simulation, launches this month in Grenoble.

North America-based manufacturers of semiconductor equipment posted $2.03 billion in billings worldwide in September 2017 (three-month average basis), according to the September Equipment Market Data Subscription (EMDS) Billings Report published today by SEMI.

SEMI reports that the three-month average of worldwide billings of North American equipment manufacturers in September 2017 was $2.03 billion.The billings figure is 6.9 percent lower than the final August 2017 level of $2.18 billion, and is 36.0 percent higher than the September 2016 billings level of $1.49 billion.

“Global semiconductor equipment billings of North American headquartered suppliers for September were $2.0 billion, down 12 percent from the peak level set in June of this year,” said Ajit Manocha, president and CEO of SEMI. “Total billings through the first three quarters of this amazing year have surpassed total billings for all of 2016.”

The SEMI Billings report uses three-month moving averages of worldwide billings for North American-based semiconductor equipment manufacturers. Billings figures are in millions of U.S. dollars.

Billings
(3-mo. avg)
Year-Over-Year
April 2017
$2,136.4
46.3%
May 2017
$2,270.5
41.8%
June 2017
$2,300.3
34.1%
July 2017
$2,269.7
32.9%
August 2017 (final)
$2,181.8
27.7%
September 2017 (prelim)
$2,031.1
36.0%

Source: SEMI (www.semi.org), October 2017
SEMI publishes a monthly North American Billings report and issues the Worldwide Semiconductor Equipment Market Statistics (WWSEMS) report in collaboration with the Semiconductor Equipment Association of Japan (SEAJ). The WWSEMS report currently reports billings by 24 equipment segments and by seven end market regions.

Microsemi Corporation (Nasdaq: MSCC), a provider of semiconductor solutions differentiated by power, security, reliability and performance, today announced the company’s new Mi-V™ ecosystem with industry leaders, to increase adoption of its RISC-V soft central processing unit (CPU) product family. The announcement comes as the company also introduces Mi-V RV32IMA and additional field programmable gate array (FPGA)-based soft CPU solutions ideally suited for designs utilizing RISC-V open instruction set architectures (ISAs).

“As a leader in RISC-V, we are pleased Microsemi is the first tier one vendor to build out a complete open RISC-V ecosystem, which not only supports our needs, but contributes to the entire development community,” said Jim Aralis, chief technology officer and vice president of advanced development at Microsemi. “Customers can now select RISC-V for their new designs knowing a tier one vendor committed to the success of this technology is providing all the necessary tools to confidently use RISC-V soft CPUs in their products.”

RISC-V, an ISA which is a standard open architecture under the governance of the RISC-V Foundation, offers numerous benefits, including portability as well as enabling the open source community to test and improve cores at a faster pace than closed ISAs. As the RISC-V intellectual property (IP) core is not encrypted, it can be used to ensure trust and certifications not possible with closed architectures. Microsemi’s new Mi-V ecosystem brings together a number of industry leaders involved in the development of RISC-V to leverage their capabilities and streamline RISC-V designs for customers.

“Micrium is pleased to join Microsemi’s Mi-V ecosystem with our highly dependable µC/OS-II real-time kernel, a full-featured embedded operating system,” said Jean Labrosse, co-founder and chief architect at Micrium. “As RISC-V continues to grow in popularity, we look forward to working closely with Microsemi to support accelerated adoption of its RISC-V soft CPU product offerings as well as the entire ecosystem’s RISC-V advancements.”

Microsemi’s Mi-V ecosystem, part of Microsemi’s Accelerate Ecosystem, contains a number of components. Design tools include Microsemi’s SoftConsole Eclipse-based integrated development environment (IDE), the firmware catalog and Libero PolarFire system-on-chip (SoC). Operating systems include Express Logic’s ThreadX, Huawei LiteOS and Micrium µC/OS-II. Boards include the RTG4™ development kit, IGLOO™2 RISC-V board from Future Electronics, PolarFire Evaluation Kit and more. Debug dongles from Microsemi and Olimex, first-stage bootloaders and numerous soft peripherals are also included. Example projects, drivers and firmware are all available on GitHub, the world’s largest repository of open source software.

Deployment of soft CPUs implemented with the R11C-V ISA is automatic and delivered to the user’s desktop via Microsemi’s IP Catalog. No end user license agreements are needed to gain access to the soft CPUs. Using RISC-V soft CPUs within the Mi-V ecosystem is simple, easy and free.

“Express Logic is pleased to be a foundational part of Microsemi’s Mi-V RISC-V ecosystem,” said William E. Lamie, President, Express Logic. “Our X-Ware Internet-of-Things (IoT) platform, including the industry-leading ThreadX RTOS with over 6.2 billion deployments, is the preferred embedded software platform for all designs requiring industrial-grade run-time solutions—making us an ideal fit for this new consortium.”

Offering low power and an open architecture, Microsemi’s PolarFire™, RTG4™, SmartFusion™2 and IGLOO™2 field programmable gate array (FPGA)-based RISC-V soft CPU cores are ideal for developing a wide variety of applications within the aerospace and defense, industrial and security markets. The Mi-V soft CPU cores make them particularly suitable for applications including guided munitions, IoT, secure communications and wireline bridging.

“The open source, royalty-free RISC-V instruction set creates a new business model for CPU designers that is garnering increasing interest and support,” said Linley Gwennap, principal analyst with The Linley Group, which named the RISC-V ISA “Best Technology of 2016” at its annual Analysts’ Choice Awards in January 2017. “By introducing the RV32IM CPU core with support from the Mi-V ecosystem, Microsemi will play an important role in boosting the adoption of RISC-V.”

Through Microsemi’s early involvement in the creation of the RISC-V Foundation, the company has an established leadership role in the emerging standard and ecosystem and is working closely with the nonprofit to ensure the ISA becomes an industry standard for a wide variety of computing devices. Ted Speers, head of product architecture and planning for Microsemi’s Programmable business unit, was appointed to the inaugural board of directors of the RISC-V Foundation in July 2016, and Ted Marena, director of SoC FPGA marketing, was recently sworn in as chair of the RISC-V Marketing Committee after serving as vice-chair since August 2016. Marena will also be the featured speaker at EE World Online’s upcoming webinar titled, “The RISC-V ecosystem is ready for prime time. Get started here!” on Oct. 25, 2017. Attendees can register online to join this event.

The Mi-V Ecosystem began as part of the Microsemi Accelerate Ecosystem, a program designed to reduce time to market for end customers and time to revenue for ecosystem participants. Microsemi’s Accelerate Ecosystem brings together leading silicon, intellectual property (IP), systems, software and design experts to deliver solutions for end customers.

The ConFab, to be held May 20-23 at The Cosmopolitan of Las Vegas, is excited to announce IBM’s Dr. Rama Divakaruni will be the opening keynote for the 2018 conference. Dr. Divakaruni’s presentation is entitled, “How AI is Driving the New Semiconductor Era“. He will address the Artificial Intelligence era demands for dramatic enhancement in computational performance and efficiency of AI workloads, and discuss the needs and changes required in algorithms, systems and chip design as well as in devices and materials.

“Increased use of artificial intelligence will radically change how semiconductors are designed and manufactured, and I’m delighted IBM’s Rama Divakaruni will be sharing his insights at The ConFab in 2018,” said Pete Singer, Editor-in-Chief of Solid State Technology and the conference chair of The ConFab.

Dr. Divakaruni is responsible for IBM Advanced Process Technology Research (which includes EUV technologies and advanced unit process and enablement technologies) and he is the main interface between IBM Semiconductor Research and IBM’s Systems Leadership. Dr. Divakaruni is an IBM Distinguished Engineer and one of IBMs top inventors with over 225 issued US patents.

An impressive background – since 1994, Dr. Divakaruni has been working on advanced semiconductor technologies at IBM. Through 2003, while in DRAM Technology Development, his team introduced the world’s first sub-8F2 vertical transistor DRAM trench technology. The next two years, Dr. Divakaruni worked as the technical lead for the 90nm strained silicon technology which was the world’s first to introduce dual stress liner technology; the technology was the basis of the Nintento Wii, XBOX360 and the PlayStation3 game platforms. After a year serving as project manager for the Unit Process team, he was program manager and technical lead for the development of 45nm industry standard bulk technologies for IBM’s Joint Development Alliance. At 45nm, IBM and its development partners introduced strained silicon technology for low power mobile products thus launching strained silicon across the spectrum of bulk low power and SOI performance CMOS technologies. This technology was the basis for the first Apple I-pad, early Apple I-phones and was the technology that IBM’s partners, including Samsung, used for all their mobile platforms and devices. 

Professor Martijn Kemerink of Linköping University has worked with colleagues in Spain and the Netherlands to develop the first material with conductivity properties that can be switched on and off using ferroelectric polarisation.

The phenomenon can be used for small and flexible digital memories of the future, and for completely new types of solar cells.

In an article published in the prestigious scientific journal Science Advances, the research group shows the phenomenon in action in three specially built molecules, and proposes a model for how it works.

This is the first material with conductivity properties that can be switched on and off using ferroelectric polarization. Credit: Thor Balkhed

This is the first material with conductivity properties that can be switched on and off using ferroelectric polarization. Credit: Thor Balkhed

“I originally had the idea many years ago, and then I just happened to meet Professor David González-Rodríguez, from the Universidad Autónoma de Madrid, who had constructed a molecule of exactly the type we were looking for,” says Martijn Kemerink.

The organic molecules that the researchers have built conduct electricity and contain dipoles. A dipole has one end with a positive charge and one with a negative charge, and changes its orientation (switches) depending on the voltage applied to it. In a thin film of the newly developed molecules, all the dipoles can be caused to switch at exactly the same time, which means that the film changes its polarisation. The property is known as ferroelectricity. In this case, it also leads to a change in the conductivity, from low to high or vice versa. When an electrical field with the opposite polarity is applied, the dipoles again switch direction. The polarisation changes, as does the ability to conduct current.

The molecules designed according to the model developed by the LiU researchers tend to spontaneously place themselves on top of each other to form a stack or a supramolecular wire, with a diameter of just a few nanometres. These wires can subsequently be placed into a matrix in which each junction constitutes one bit of information. This will make it possible in the future to construct extremely small digital memories with very high information density. The synthesis of the new molecules is, however, still too complicated for practical use.

“We have developed a model for how the phenomenon arises in principle, and we have shown experimentally that it works for three different molecules. We now need to continue work to build molecules that can be used in practical applications,” says Professor Martijn Kemerink, from Complex Materials and Devices at Linköping University, and principal author of the article.