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Samsung Electronics Co., Ltd. today announced that it has begun mass production of a 256-gigabyte (GB) embedded Universal Flash Storage (eUFS) solution with advanced features based on automotive specifications from the JEDEC UFS 3.0 standard, for the first time in the industry.

Following the memory breakthrough of the automotive industry’s first 128GB eUFS in September, 2017, Samsung’s automotive 256GB eUFS is now being shipped to automotive manufacturers preparing the market for Advanced Driver Assistance Systems (ADAS), next-generation infotainment systems and new-age dashboards in luxury vehicles.

As thermal management is crucial for automotive memory applications, Samsung’s 256GB eUFS extends the temperature range to between -40°C and 105°C for both operational and power-saving modes. Warranties for conventional embedded multimedia card (eMMC) 5.1 solutions generally cover -25°C to 85°C for vehicles in operation and -40°C to 85°C when in idle or power-saving mode.

“With the new temperature threshold for automobile warranties, major automotive manufacturers can now design-in memory that’s even well suited for extreme environments and know they will be getting highly reliable performance,” said Kyoung Hwan Han, vice president of NAND marketing at Samsung Electronics. “Starting with high-end vehicles, we expect to expand our business portfolio across the entire automotive market, while accelerating growth in the premium memory segment.”

Samsung’s 256GB eUFS not only can easily endure the new temperature specification, despite the heat-sensitive nature of memory storage, but also through its temperature notification feature, a sensor will notify the host application processor (AP) when the device temperature exceeds 105°C or any pre-set level. The AP would then regulate its clock speed to lower the temperature to an acceptable level.

Sequential reads for the 256GB eUFS can reach 850 megabytes per second (MB/s), which is at the high end of the current JEDEC UFS 2.1 standard, and random read operations come in at 45,000 IOPS. In addition, a data refresh feature speeds up processing and enables greater system reliability by relocating older data to other less-used cells.

The temperature notification, developed by Samsung, and data refresh features are included in UFS specification, version 3.0, which was announced last month by JEDEC, a global semiconductor standards organization.

Samsung plans to bolster its technology partnerships with global automakers and component providers, and continue expanding its eUFS line-up with an aim to lead the premium memory market.

At DESY’s X-ray source PETRA III, scientists have followed the growth of tiny wires of gallium arsenide live. Their observations reveal exact details of the growth process responsible for the evolving shape and crystal structure of the crystalline nanowires. The findings also provide new approaches to tailoring nanowires with desired properties for specific applications. The scientists, headed by Philipp Schroth of the University of Siegen and the Karlsruhe Institute of Technology (KIT), present their findings in the journal Nano Letters. The semiconductor gallium arsenide (GaAs) is widely used, for instance in infrared remote controls, the high-frequency components of mobile phones and for converting electrical signals into light for fibre optical transmission, as well as in solar panels for deployment in spacecraft.

To fabricate the wires, the scientists employed a procedure known as the self-catalysed Vapour-Liquid-Solid (VLS) method, in which tiny droplets of liquid gallium are first deposited on a silicon crystal at a temperature of around 600 degrees Celsius. Beams of gallium atoms and arsenic molecules are then directed at the wafer, where they are adsorpted and dissolve in the gallium droplets. After some time, the crystalline nanowires begin to form below the droplets, whereby the droplets are gradually pushed upwards. In this process, the gallium droplets act as catalysts for the longitudinal growth of the wires. “Although this process is already quite well established, it has not been possible until now to specifically control the crystal structure of the nanowires produced by it. To achieve this, we first need to understand the details of how the wires grow,” emphasises co-author Ludwig Feigl from KIT.

To observe the growth as it takes place, Schroth’s group installed a mobile experimental chamber, specially developed by KIT for X-ray experiments and partially funded by the Federal Ministry of Education and Research (BMBF), in the brilliant X-ray beam of DESY’s synchrotron radiation source PETRA III at experimental station P09. At one-minute intervals the scientists took X-ray pictures, which allowed both the internal structure and the diameter of the growing nanowires to be simultaneously determined. In addition, they measured the fully-grown nanowires using the scanning electron microscope at the DESY NanoLab. “To ensure the success of such complex measurements, an extensive period of growth characterisation and optimisation at the UHV Analysis Lab at KIT was a prerequisite,” explains co-author Seyed Mohammad Mostafavi Kashani from University of Siegen.

Over a period of about four hours, the wires grew to a length of some 4000 nanometres. One nanometre (nm) is one millionth of a millimetre. However, not only did the wires become longer during this time, but also thicker: their diameter increased from an initial 20 nm to up to 140 nm at the top of the wire, still making them around 500 times thinner than a human hair.

“One rather exciting feature is that the images taken under the electron microscope show the nanowires to have a slightly different shape,” says co-author Thomas Keller from DESY NanoLab. Although the wires were thicker at the top than at the bottom, just as indicated by the X-ray data, the diameter measured under the electron microscope was larger in the lower region of the wire than what was observed using X-rays.

“We found out that the growth of the nanowires is not only due to the VLS mechanism but that a second component also contributes, which we were able to observe and quantify for the first time in this experiment. This additional sidewall growth lets the wires gain width,” explains Schroth. Independently of VLS growth, the vapour deposited material also attaches itself directly to the side walls, particularly in the lower region of the nanowire. This additional contribution can be determined by comparing the X-ray measurements taken early on during the growth of the wire, with the electron microscope measurement after growth has ended.

Furthermore, the gallium droplets are constantly becoming larger as further gallium is added in the course of the growth process. Using growth models, the scientists were able to deduce the shape of the droplets, which had also been affected by the increasing droplet size. The effect of this is far-reaching: “As the droplet changes in size, the angle of contact between the droplet and the surface of the wires also changes. Under certain circumstances, the wire then suddenly continues growing with a different crystal structure,” says Feigl. Whereas the fine nanowires initially crystallise in a hexagonal, so-called wurtzite structure, this behaviour changes after some time and the wires adopt a cubic zinc blende structure as they continue to grow. This change is important when it comes to applications, since the structure and shape of the nanowires have important consequences for the properties of the resulting material.

Such detailed findings not only lead to a better understanding of the growth process; they also provide approaches for customising future nanowires to have special properties for specific applications – for example to improve the efficiency of a solar cell or a laser.

This research is also part of the strategic collaboration between the two Helmholtz Centres KIT and DESY within the framework of the Helmholtz programme “From Matter to Materials and Life” (MML).

DESY is one of the world’s leading particle accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – ranging from the interaction of tiny elementary particles to the behaviour of innovative nanomaterials and the vital processes that take place between biomolecules to the great mysteries of the universe. The accelerators and detectors that DESY develops and builds at its locations in Hamburg and Zeuthen are unique research tools. DESY is a member of the Helmholtz Association, and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent).

Leti Chief Scientist Barbara De Salvo will help kick off ISSCC 2018 with an opening-day presentation calling for radically new, digital-communication architecture for the Internet of Things in which “a great deal of analytics processing occurs at the edge and at the end devices instead of in the Cloud.”

Delivering a keynote talk during the Feb. 12 plenary session that formally opens the conference, De Salvo will note that the architecture will include human-brain inspired hardware coupled to new computing paradigms and algorithms that “will allow for distributed intelligence over the whole IoT network, all-the-way down to ultralow-power end-devices.”

“We are entering a new era where artificial-intelligence systems are … shaping the future world,” says De Salvo, who also is Leti’s scientific director. “With the end of Moore’s Law in sight, transformative approaches are needed to address the enduring power-efficiency issues of traditional computing architectures.”

Leti paper and demo present technology for ‘extracting energy from shocks’

In addition, Leti scientists will present a paper on and a demonstration of real-life applications of piezoelectric energy harvesting, which converts mechanical energy, such as vibration and shocks, into electrical energy. The demo at Demonstration Session 1, 8.8, from 5-7 p.m., Feb. 12, in Golden Gate Hall of the San Francisco Marriott Marquis Hotel, will show a new technology for extracting energy from shocks. The demo shows an energy-autonomous temperature sensor node powered by the proposed harvesting circuit in an automotive environment. The system is able to harvest enough energy to sense temperature and transmit it wirelessly with a few mechanical pulses.

 

The demonstration is based on the paper, “A 30nA Quiescent 80nW-to-14mW Power-Range Shock-Optimized SECE-Based Piezoelectric Harvesting Interface with 420% Harvested-Energy Improvement”. The paper will be presented at 11:15 a.m., Feb. 13, during Session 8 on Wireless Power and Harvesting. The authors propose an efficient electrical interface to maximize the energy extraction from a piezoelectric energy harvester. The novelty of the approach is to adapt the strategy to sporadic mechanical shocks, usually found in real-environments, instead of periodic vibrations. The circuit allows a self-starting operation and energy-aware sequencing with nanowatt power consumption. Compared to a well-established interface, the proposed approach presents 4x energy harvesting capability.

INFICON,a manufacturer of leak test equipment, introduced the UL3000 Fab leak detector for semiconductor manufacturing maintenance teams to easily check the tightness of vacuum chambers for wafer production. Special advantages of the new leak detector are its fast readiness and unrivaled simplicity enabling the operator to find leaks of all sizes with the same procedures. It also has a slim mobile design for easy maneuverability and an intuitive operating concept for easy operation. The UL3000 Fab, which uses helium as a test gas, detects even the smallest leakage rates up to 5 x 10-12 atm cc/, thus providing the highest seal confirmation tightness of vacuum chambers for wafer production.

Daniel Hoffman, Sales and Service Manager for Leak Detection in the Americas, sees the new model as a big step forward. “Constantly innovating and optimizing our products to meet customer needs is a core goal for INFICON. With our new UL3000 Fab we will enable leak detection productivity gains never before seen in the semiconductor leak testing process,” said Hoffman.

The powerful, compact and smart leak detector enables testing at atmospheric pressure (through MASSIVE leak function) with best in class time to test or background generation, saturation protection, smart power and PM saving control all in a compact package. With its narrow design (only 18.6 inches wide), the mobile leak detector is designed for high maneuverability. Also, UL3000 Fab features robust construction, a deep center of gravity and large tires to ensure optimum mobility.

UL3000Fab_sil_right_MEDIUM

When it comes to biometric sensors, human skin isn’t an ally.

It’s an obstacle.

The University of Cincinnati is developing cutting-edge methods to overcome this barrier without compromising the skin and its ability to prevent infection and dehydration. By making better noninvasive tests, researchers can open up enormous opportunities in medicine and the fitness industry.

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UC engineering student Adam Hauke holds up the latest generation of wearable sensor in UC’s Novel Devices Lab. Credit: Joseph Fuqua II/UC Creative Services

“You think of the skin as an opportunity because you can measure things through it optically, chemically, electrically and mechanically,” said Jason Heikenfeld, assistant vice president in UC’s College of Engineering and Applied Science. “But it’s actually the opposite. The body has evolved to preserve all of these chemical analytes. So the skin actually isn’t very good at giving them up.”

Heikenfeld, director of UC’s Novel Devices Lab, co-authored a critical review of sensor research this month with his students and colleagues for the nanotechnology journal Lab on a Chip, outlining both scientific accomplishments to date and challenges ahead.

“We wanted to have all of the current progress and future directions and needs consolidated in one article,” said Andrew Jajack, co-author and a UC engineering student. Jajack designed the image and graphic that appears on the journal’s cover depicting the four ways that sensors can read biometrics in a track athlete.

The article, co-authored by international leaders in biosensors, discussed the growing popularity of wearable devices such as Fitbit and explored the limitations of current technology.

The skin can provide misleading data to biosensors since it harbors bacteria and tends to collect salt and other minerals from dried sweat. An effective sensor has to bend and stretch like human skin, even as it adheres to the surface when the subject is moving. Electrical sensors that track your heartbeat have to account for noise both from within the body or the environment such as from power lines or nearby electronics.

Heikenfeld said biosensors in most wearable devices use technology that has been available for years.

“The latest trend has not been driven by technological breakthroughs,” he said. “When you think of Fitbit, these capabilities have been around a long time. What’s driven it is the proliferation of smartphones and miniaturization of electronics and a growing desire for health awareness.”

UC has a long history with biosensors. The late Leland Clark Jr., sometimes called “the father of biosensors,” conducted research at the UC College of Medicine and Cincinnati Children’s Hospital Research Foundation. Among his many feats, he developed the modern blood glucose monitor that diabetics use today and the first sensors to measure a patient’s blood oxygen levels.

“Sensors are a big deal here,” Heikenfeld said. “It’s something we’ve had historical strength in with pioneers in the field.”

UC’s research in sensors continues to be a pipeline for industry. Heikenfeld is co-founder and chief science officer for Eccrine Systems Inc., a Cincinnati company that specializes in sweat biosensors.

Eccrine Systems announced this month that it won a $750,000 contract with the U.S. Air Force to study biomarkers from human sweat in real time. It marks the second phase of an initial research contract with the military.

“We try to know other people’s business better than they do. You can’t innovate unless you are willing to dig way deeper than the competition,” he said.

Jajack said Eccrine Systems, Inc. is working on new ways to track biometric information continuously over time.

“A lot of the way we diagnose disease is based on single-moment-in-time markers. But the promise of wearable sensors is real-time health monitoring,” he said. “You can see a more complex picture of what’s going on in the body. That alone will lead to more diagnostic techniques across a spectrum of diseases.”

Students in UC’s Novel Devices Lab, located in the College of Engineering and Applied Science, are coming up with innovative ways to glean information from human sweat. These devices are the size of a Band-Aid and are worn on the skin like one, too.

Students Adam Hauke and Phillip Simmers are working on UC’s next generation of sweat-stimulating sensors. These devices generate sweat on a tiny patch of skin, even when the subject is resting and comfortable, and wick it away to sensors that measure substances like glucose. The biosensors collect and concentrate the faintest amounts of sweat into samples that sensors can read.

“We’ll stimulate sweating in this area and then this will start to pick up sweat off the skin, pulling it from the pores and moving it up across these electrodes here,” Hauke said. “That’s where we do the sensing.”

Among its other capabilities, the device measures the galvanic skin response, an indication of how much someone is sweating, he said.

“The more you sweat, the wetter your skin is and the electrical resistance goes down,” he said.

The Society for Chemistry and Micro-Nano Systems recognized Hauke and Simmers with its Young Researcher Award last year for their collaborative study in continuous sweat sampling and sensing.

In a different part of the Novel Devices Lab, engineering student Laura Stegner worked with a milling machine to customize flow-rate sensors. Across from her, classmate Amy Drexelius worked on the part of the device that can separate and concentrate the analytes they want to test in sweat or blood.

“We want to concentrate the sample. So you can stick this on the front of your sensor and it does a lot of previously hard chemistry lab work for you,” she said.

This technique could apply to other trace chemicals scientists want to measure, Jajack said.

“A big issue today is the amount of pharmaceuticals found in our drinking water,” Jajack said. “They’re hard to measure because they’re so diluted. Even at diluted concentrations, they might be having an effect on us.”

Heikenfeld said his lab’s success stems from its talented students, who apply their diverse interests and experiences to their lab work. Developing new sensors and applications takes problem solving that draws from many academic disciplines.

“How often are you going to find someone who’s deep into biology and chemistry who also does hack-athons and is a big maker, too?” Heikenfeld said of Jajack. “But that’s what it’s going to take. We need to innovate in disciplines that are not our traditional areas of expertise so we’re not relying on others to move at speeds at which our own creative minds want to sprint. We’re doing that now because of the quality of people we have here.”

Moving sensor applications from the lab bench to the store shelf remains a big challenge, UC chemistry professor William Connick said. He serves as director of UC’s Center for Biosensors & Chemical Sensors.

“Groups like Dr. Heikenfeld’s are making remarkable strides in developing technologies that provide information on biomarkers at exceedingly low levels from very small quantities of fluid like sweat,” Connick said.

“To go from the lab to a practical device is a challenge when you’re working with real-world samples. Every person is a little different. Every circumstance is a little different,” he said. “Making something that’s robust enough to accurately perform under a wide variety of conditions is challenging.”

Connick said demand for biosensors is only going to grow as labs like UC’s develop better ways to collect information. And home testing and continuous monitoring of drugs over time could lead to better health outcomes, he said.

“The market is wide open now. The potential is gigantic, just in cost savings and being able to provide rapid screening without taking blood and having to send samples off to a laboratory,” Connick said.

Heikenfeld’s journal article noted that biosensors of the future will measure multiple aspects of a person’s physiology. And new wearable sensors will need a mix of disposable and reusable parts to address the wear and tear that come with daily life.

Now UC’s Novel Devices Lab is developing a new noninvasive technique to make sweat glands more permeable so sensors can record even more detailed data. Heikenfeld and Jajack are not ready to talk about how it works but they are very excited about the possibilities.

“Let’s just say it’s safe and super awesome,” Heikenfeld said. “There are a lot of great things coming up.”

MACOM Technology Solutions Holdings, Inc. (NASDAQ: MTSI) (“MACOM”), a supplier of high-performance RF, microwave, millimeterwave and lightwave semiconductor products, and STMicroelectronics (NYSE: STM) today announced an agreement to develop GaN (Gallium Nitride) on Silicon wafers to be manufactured by ST for MACOM’s use across an array of RF applications. While expanding MACOM’s source of supply, the agreement also grants to ST the right to manufacture and sell its own GaN on Silicon products in RF markets outside of mobile phone, wireless basestation and related commercial telecom infrastructure applications.

Through this agreement, MACOM expects to access increased Silicon wafer manufacturing capacity and improved cost structure that could displace incumbent Silicon LDMOS and accelerate the adoption of GaN on Silicon in mainstream markets. ST and MACOM have been working together for several years to bring GaN on Silicon production up in ST’s CMOS wafer fab. As currently scheduled, sample production from ST is expected to begin in 2018.

“This agreement punctuates our long journey of leading the RF industry’s conversion to GaN on Silicon technology. To date, MACOM has refined and proven the merits of GaN on Silicon using rather modest compound semiconductor factories, replicating and even exceeding the RF performance and reliability of expensive GaN on SiC alternative technology,” said John Croteau, President and CEO, MACOM. “We expect this collaboration with ST to bring those GaN innovations to bear in a Silicon supply chain that can ultimately service the most demanding customers and applications.”

“ST’s scale and operational excellence in Silicon wafer manufacturing aims to unlock the potential to drive new RF power applications for MACOM and ST as it delivers the economic breakthroughs necessary to expand the market for GaN on Silicon,” said Marco Monti, President of the Automotive and Discrete Product Group, STMicroelectronics. “While expanding the opportunities for existing RF applications is appealing, we’re even more excited about using GaN on Silicon in new RF Energy applications, especially in automotive applications, such as plasma ignition for more efficient combustion in conventional engines, and in RF lighting applications, for more efficient and longer-lasting lighting systems.”

“Once the $0.04/watt barrier for high power RF semiconductor devices is crossed, significant opportunities for the RF energy market may open up,” said Eric Higham, Director Advanced Semiconductor Applications Service at Strategy Analytics. Higham continued, “Potential RF energy device shipments could be in the hundreds of millions for applications including commercial microwave cooking, automotive lighting and ignition, and plasma lighting, with sales reaching into the billions of dollars.”

Texas Instruments (TI) (NASDAQ: TXN) today introduced the industry’s smallest operational amplifier (op amp) and low-power comparators at 0.64 mm2. As the first amplifiers in the compact X2SON package, the TLV9061 op amp and TLV7011 family of comparators enable engineers to reduce their system size and cost, while maintaining high performance in a variety of Internet of Things (IoT), personal electronics and industrial applications, including mobile phones, wearables, optical modules, motor drives, smart grid and battery-powered systems.

With a high gain bandwidth (GBW) of 10 MHz, fast slew rate at 6.5 V/µs and low-noise spectral density of 10 nV/√Hz, the TLV9061 op amp is designed for use in wide-bandwidth, high-performance systems. The TLV7011 family of nanopower comparators delivers a faster response time with propagation delays down to 260 ns, while consuming 50 percent less power than competitive comparators. Additionally, both devices support rail-to-rail inputs with low-voltage operation down to 1.8 V, enabling ease-of-use in battery-powered applications.

Achieve high performance in tiny spaces with the TLV9061 operational amplifier

  • Reduces system size and cost: In addition to its tiny size, the TLV9061 op amp also features integrated EMI filtering inputs. This helps provide resilient performance for systems prone to RF noise, while significantly reducing the need for external discrete circuitry.
  • Greater DC accuracy: Two times lower offset drift and typical input bias across a full temperature range, -40 to 125 degrees Celsius, creates a more precise signal chain solution compared to other small devices.

Lower power, faster response with the tiny TLV7011 family of comparators

  • Smaller footprint, extra features: No phase reversal and integrated internal hysteresis for overdriven inputs increase design flexibility and reduce the need for external components.
  • Fifty percent less power consumption: With power as low as 335 nA and fast propagation delay down to 260 ns, the TLV7011 family of nanopower comparators enable low-power systems to monitor signals and respond quickly.

These new devices join TI’s small-size amplifier portfolio which enables engineers to design smaller systems, while maintaining high performance, with industry-leading package options and many of the world’s smallest op amps and comparators.

Tools and support to speed design
Designers can download the TINA-TI™ SPICE model to simulate their designs and predict circuit behavior when using the TLV9061 op amp and TLV7011 family of comparators. Engineers can jump-start their small brushed DC servo drive designs using the TLV9061 op amp with the 10.8-V/15-W, >90% Efficiency, 2.4-cm2, Power Stage Reference Design. Also, they can quickly and easily evaluate the TLV7011 comparators with the DIP adapter evaluation module, available today for US$5.00 from the TI store and authorized distributors.

Package, availability and pricing
Preproduction samples of the TLV9061 op amp and volume quantities of the TLV7011 family of comparators are now available through the TI store and authorized distributors in a 5-pin extra small outline no-lead (X2SON) package, measuring 0.8 mm x 0.8 mm x 0.4 mm. Pricing starts at US$0.19 and US$0.25 in 1,000-unit quantities, respectively. Learn more about the family of comparators in the table below.

Product

Supply
voltage (Vcc)

DC input
offset (Vios)

Propagation
delay (tpd)

Supply
current (Icc)

TLV7011

1.6 – 5.5 V

0.5 mV

260 ns

5 µA

TLV7021

1.6 – 5.5 V

0.5 mV

260 ns

5 µA

TLV7031

1.6 – 6.5 V

0.1 mV

3 µs

335 nA

TLV7041

1.6 – 6.5 V

0.1 mV

3 µs

335 nA

Graphene is a remarkable material: light, strong, transparent and electrically conductive. It can also convert heat to electricity. Researchers have recently exploited this thermoelectric property to create a new kind of radiation detector.

Classified as a bolometer, the new device has a fast response time and, unlike most other bolometers, works over a wide range of temperatures. With a simple design and relatively low cost, this device could be scaled up, enabling a wide range of commercial applications. Researchers describe a graphene-based radiation detector this week in Applied Physics Letters, from AIP Publishing.

The discovery of graphene in 2004 was anticipated to herald a whole new type of technology. “But unfortunately, there are some strong fundamental limitations for this material,” said Grigory Skoblin of Chalmers University of Technology in Sweden. “Nowadays, the real industrial applications of graphene are quite limited.”

Graphene — composed of single sheets of carbon atoms that form a flat, hexagonal lattice structure — has been used mainly for its mechanical properties.

“But our device shows that more fundamental properties can be used in actual applications,” Skoblin said. The new bolometer is based on graphene’s thermoelectric properties. Radiation heats part of the device, inducing electrons to move. The displaced electrons generate an electric field, which creates a voltage difference across the device. The change in voltage thus provides an essentially direct measurement of the radiation.

Other devices rely on the generation of electrical current or resistance change by incoming radiation. But measuring changes in current or resistance requires an external power source to generate an initial current. The mechanism is much simpler than in other bolometers, according to Skoblin.

The piece of graphene in the new bolometer is small, so it’s one of the fastest bolometers because it heats up and responds quickly. Furthermore, the device remains sensitive to radiation at temperatures up to 200 degrees Celsius. Conventional bolometers typically work only at cryogenic temperatures.

Other researchers have previously made graphene bolometers, with better properties than this new device, but these models contain a double layer of graphene, making them more difficult to scale, Skoblin said.

Another advantage of the new device is its coating. The researchers previously developed a method to coat graphene with a dielectric polymer called Parylene, which offers a good balance of performance and scalability. You can get better performance by coating with hexagonal boron nitride, Skoblin said, but it’s hard to acquire and the coating techniques are difficult to scale up. Other studies suggest that a bolometer with hexagonal boron nitride coating would be less efficient.

The prototype bolometer works only with microwave radiation at 94 gigahertz, but future designs will widen the frequency range. Next, the researchers plan to make the device using chemical vapor deposition to grow larger pieces of graphene, paving the way for mass production.

First came the switch. Then the transistor. Now another innovation stands to revolutionize the way we control the flow of electrons through a circuit: vanadium dioxide (VO2). A key characteristic of this compound is that it behaves as an insulator at room temperature but as a conductor at temperatures above 68°C. This behavior – also known as metal-insulator transition – is being studied in an ambitious EU Horizon 2020 project called Phase-Change Switch. EPFL was chosen to coordinate the project following a challenging selection process.

The project will last until 2020 and has been granted €3.9 million of EU funding. Due to the array of high-potential applications that could come out of this new technology, the project has attracted two major companies – Thales of France and the Swiss branch of IBM Research – as well as other universities, including Max-Planck-Gesellschaft in Germany and Cambridge University in the UK. Gesellschaft für Angewandte Mikro- und Optoelektronik (AMO GmbH), a spin-off of Aachen University in Germany, is also taking part in the research.

Scientists have long known about the electronic properties of VO2 but haven’t been able to explain them until know. It turns out that its atomic structure changes as the temperature rises, transitioning from a crystalline structure at room temperature to a metallic one at temperatures above 68°C. And this transition happens in less than a nanosecond – a real advantage for electronics applications. “VO2 is also sensitive to other factors that could cause it to change phases, such as by injecting electrical power, optically, or by applying a THz radiation pulse,” says Adrian Ionescu, the EPFL professor who heads the school’s Nanoelectronic Devices Laboratory (Nanolab) and also serves as the Phase-Change Switch project coordinator.

The challenge: reaching higher temperatures

However, unlocking the full potential of VO2 has always been tricky because its transition temperature of 68°C is too low for modern electronic devices, where circuits must be able to run flawlessly at 100°C. But two EPFL researchers – Ionescu from the School of Engineering (STI) and Andreas Schüler from the School of Architecture, Civil and Environmental Engineering (ENAC) – may have found a solution to this problem, according to their joint research published in Applied Physics Letters in July 2017. They found that adding germanium to VO2 film can lift the material’s phase change temperature to over 100°C.

Even more interesting findings from the Nanolab – especially for radiofrequency applications – were published in IEEE Access on 2 February 2018. For the first time ever, scientists were able to make ultra-compact, modulable frequency filters. Their technology also uses VO2 and phase-change switches, and is particularly effective in the frequency range crucial for space communication systems (the Ka band, with programmable frequency modulation between 28.2 and 35 GHz).

Neuromorphic processors and autonomous vehicles

These promising discoveries are likely to spur further research into applications for VO2 in ultra-low-power electronic devices. In addition to space communications, other fields could include neuromorphic computing and high-frequency radars for self-driving cars.

Researchers at the University of Illinois at Chicago describe a new technique for precisely measuring the temperature and behavior of new two-dimensional materials that will allow engineers to design smaller and faster microprocessors. Their findings are reported in the journal Physical Review Letters.

Newly developed two-dimensional materials, such as graphene — which consists of a single layer of carbon atoms — have the potential to replace traditional microprocessing chips based on silicon, which have reached the limit of how small they can get. But engineers have been stymied by the inability to measure how temperature will affect these new materials, collectively known as transition metal dichalcogenides, or TMDs.

Using scanning transmission electron microscopy combined with spectroscopy, researchers at UIC were able to measure the temperature of several two-dimensional materials at the atomic level, paving the way for much smaller and faster microprocessors. They were also able to use their technique to measure how the two-dimensional materials would expand when heated.

“Microprocessing chips in computers and other electronics get very hot, and we need to be able to measure not only how hot they can get, but how much the material will expand when heated,” said Robert Klie, professor of physics at UIC and corresponding author of the paper. “Knowing how a material will expand is important because if a material expands too much, connections with other materials, such as metal wires, can break and the chip is useless.”

Traditional ways to measure temperature don’t work on tiny flakes of two-dimensional materials that would be used in microprocessors because they are just too small. Optical temperature measurements, which use a reflected laser light to measure temperature, can’t be used on TMD chips because they don’t have enough surface area to accommodate the laser beam.

“We need to understand how heat builds up and how it is transmitted at the interface between two materials in order to build efficient microprocessors that work,” said Klie.

Klie and his colleagues devised a way to take temperature measurements of TMDs at the atomic level using scanning transition electron microscopy, which uses a beam of electrons transmitted through a specimen to form an image.

“Using this technique, we can zero in on and measure the vibration of atoms and electrons, which is essentially the temperature of a single atom in a two-dimensional material,” said Klie. Temperature is a measure of the average kinetic energy of the random motions of the particles, or atoms that make up a material. As a material gets hotter, the frequency of the atomic vibration gets higher. At absolute zero, the lowest theoretical temperature, all atomic motion stops.

Klie and his colleagues heated microscopic “flakes” of various TMDs inside the chamber of a scanning transmission electron microscope to different temperatures and then aimed the microscope’s electron beam at the material. Using a technique called electron energy-loss spectroscopy, they were able to measure the scattering of electrons off the two-dimensional materials caused by the electron beam. The scattering patterns were entered into a computer model that translated them into measurements of the vibrations of the atoms in the material – in other words, the temperature of the material at the atomic level.

“With this new technique, we can measure the temperature of a material with a resolution that is nearly 10 times better than conventional methods,” said Klie. “With this new approach, we can design better electronic devices that will be less prone to overheating and consume less power.”

The technique can also be used to predict how much materials will expand when heated and contract when cooled, which will help engineers build chips that are less prone to breaking at points where one material touches another, such as when a two-dimensional material chip makes contact with a wire.

“No other method can measure this effect at the spatial resolution we report,” said Klie. “This will allow engineers to design devices that can manage temperature changes between two different materials at the nano-scale level.”