Yearly Archives: 2017

Columbia Engineering researchers, led by Harish Krishnaswamy, associate professor of electrical engineering, in collaboration with Professor Andrea Alu’s group from UT-Austin, continue to break new ground in developing magnet-free non-reciprocal components in modern semiconductor processes. At the IEEE International Solid-State Circuits Conference in February, Krishnaswamy’s group unveiled a new device: the first magnet-free non-reciprocal circulator on a silicon chip that operates at millimeter-wave frequencies (frequencies near and above 30GHz). Following up on this work, in a paper (DOI 10.1038/s41467-017-00798-9) published today in Nature Communications, the team demonstrated the physical principles behind the new device.

Most devices are reciprocal: signals travel in the same manner in forward and reverse directions. Nonreciprocal devices, such as circulators, on the other hand, allow forward and reverse signals to traverse different paths and therefore be separated. Traditionally, nonreciprocal devices have been built from special magnetic materials that make them bulky, expensive, and not suitable for consumer wireless electronics.

The team has developed a new way to enable nonreciprocal transmission of waves: using carefully synchronized high-speed transistor switches that route forward and reverse waves differently. In effect, it is similar to two trains approaching each other at super-high speeds that are detoured at the last moment so that they do not collide.

The key advance of this new approach is that it enables circulators to be built in conventional semiconductor chips and operate at millimeter-wave frequencies, enabling full-duplex or two-way wireless. Virtually all electronic devices currently operate in half-duplex mode at lower radio-frequencies (below 6GHz), and consequently, we are rapidly running out of bandwidth. Full-duplex communications, in which a transmitter and a receiver of a transceiver operate simultaneously on the same frequency channel, enables doubling of data capacity within existing bandwidth. Going to the higher mm-wave frequencies, 30GHz and above, opens up new bandwidth that is not currently in use.

“This gives us a lot more real estate,” notes Krishnaswamy, whose Columbia High-Speed and Mm-wave IC (CoSMIC) Lab has been working on silicon radio chips for full duplex communications for several years. His method enables loss-free, compact, and extremely broadband non-reciprocal behavior, theoretically from DC to daylight, that can be used to build a wide range of non-reciprocal components such as isolators, gyrators, and circulators.

“This mm-wave circulator enables mm-wave wireless full-duplex communications, Krishnaswamy adds, “and this could revolutionize emerging 5G cellular networks, wireless links for virtual reality, and automotive radar.”

The implications are enormous. Self-driving cars, for instance, require low-cost fully-integrated millimeter-wave radars. These radars inherently need to be full-duplex, and would work alongside ultra-sound and camera-based sensors in self-driving cars because they can work in all weather conditions and during both night and day. The Columbia Engineering circulator could also be used to build millimeter-wave full-duplex wireless links for VR headsets, which currently rely on a wired connection or tether to the computing device.

“For a smooth wireless VR experience, a huge amount of data has to be sent back and forth between the computer and the headset requiring low-latency bi-directional communication,” says Krishnaswamy. “A mm-wave full-duplex transceiver enabled by our CMOS circulator could be a promising solution as it has the potential to deliver high speed data with low latency, in a small size with low cost.”

The team, funded by sources including the National Science Foundation EFRI program, the DARPA SPAR program, and Texas Instruments, is currently working to improve the linearity and isolation performance of their circulator. Their long-term goal is to build a large-scale mm-wave full-duplex phased array system that uses their circulator.

Global power semiconductor revenues grew year-over-year by 3.9 percent in 2016, reversing a 4.8 percent decline in 2015, according to a recent report from business information provider IHS Markit (Nasdaq: INFO).

All categories of power semiconductors (power discretes, power modules, and power integrated circuits) were up for the year, with the discretes market seeing the biggest jump. Sales in all regions increased, with China revenues topping the list. IHS Markit expects the market to grow by 7.5 percent in 2017, to $38.3 bill and achieve yearly increases through 2021.

Automotive and industrial lead the way

The automotive and industrial segments were particularly strong in 2016, with power semis in automotive growing by 7.0 percent and industrial by 5.0 percent. Advanced driver assistance systems (ADAS) – such as blind-spot detection, collision avoidance, and adaptive cruise control – are moving from luxury to mid-level vehicles, driving double digit increases for power semiconductors in that category.

Power semiconductors, especially power modules and discretes also saw sharp gains as the number of cars equipped with inverter systems for advanced start/stop and hybrid powertrains increased. In particular, power modules for cars and light trucks jumped 29.3 percent in 2016.

In the broad industrial sector the drive for energy efficiency improvement led to growth in renewable energy (solar and wind inverters), building and home control, and factory automation applications. Revenues from home appliances in the consumer segment also grew nicely as advanced motor control systems found their way into white goods, fans, kitchen, and cleaning products.

Despite good gains, other categories were flat to down. Power module sales for industrial motor drives, a large sub-segment, slid 1.1 percent and modules for traction applications were down 17.5 percent for the year.  Power ICs for consumer application declined 4.9 percent while power discretes for lighting applications were off 2.7 percent.

Growth to continue

“The industry megatrends of vehicle electrification, advanced vehicle safety, energy efficiency and connected everything will continue to drive growth over the next five years,” said Kevin Anderson, senior analyst, power management for IHS Markit. “IHS Markit predicts that the compound-average annual growth rate (CAGR) from 2016 – 2021 will be 4.8 percent.  Regionally, the highest growth is projected in China, at 6.0 percent CAGR, followed closely by the rest of Asia including Taiwan, Europe, Middle East and Africa, and the Americas – all with projected growth over 5 percent.”

As microchips become ever smaller and therefore faster, the shrinking size of their copper interconnects leads to increased electrical resistivity at the nanoscale. Finding a solution to this impending technical bottleneck is a major problem for the semiconductor industry.

One promising possibility involves reducing the resistivity size effect by altering the crystalline orientation of interconnect materials. A pair of researchers from Rensselaer Polytechnic Institute conducted electron transport measurements in epitaxial single-crystal layers of tungsten (W) as one such potential interconnect solution. They performed first-principles simulations, finding a definite orientation-dependent effect. The anisotropic resistivity effect they found was most marked between layers with two particular orientations of the lattice structure, namely W(001) and W(110). The work is published this week in the Journal of Applied Physics, from AIP Publishing.

The measured resistivity of epitaxial tungsten layers with (001) and (011) crystal orientation vs thickness d. The tungsten Fermi surface is color coded according to the wave vector dependent Fermi velocity vf. At small thickness, where surface scattering dominates, W(011) is nearly twice as conductive as W(001). Transport simulations indicate that this is due to the anisotropy in the Fermi surface. These results indicate how narrow wires in future computer chips can be made two times more conductive, effectively reducing the required electric power by 50 percent. Credit: Daniel Gall, Rensselaer Polytechnic Institute

The measured resistivity of epitaxial tungsten layers with (001) and (011) crystal orientation vs thickness d. The tungsten Fermi surface is color coded according to the wave vector dependent Fermi velocity vf. At small thickness, where surface scattering dominates, W(011) is nearly twice as conductive as W(001). Transport simulations indicate that this is due to the anisotropy in the Fermi surface. These results indicate how narrow wires in future computer chips can be made two times more conductive, effectively reducing the required electric power by 50 percent. Credit: Daniel Gall, Rensselaer Polytechnic Institute

Author Pengyuan Zheng noted that both the 2013 and 2015 International Technology Roadmap for Semiconductors (ITRS) called for new materials to replace copper as interconnect material to limit resistance increase at reduced scale and minimize both power consumption and signal delay.

In their study, Zheng and co-author Daniel Gall chose tungsten because of its asymmetric Fermi surface — its electron energy structure. This made it a good candidate to demonstrate the anisotropic resistivity effect at the small scales of interest. “The bulk material is completely isotropic, so the resistivity is the same in all directions,” Gall said. “But if we have thin films, then the resistivity varies considerably.”

To test the most promising orientations, the researchers grew epitaxial W(001) and W(110) films on substrates and conducted resistivity measurements of both while immersed in liquid nitrogen at 77 Kelvin (about -196 degrees Celsius) and at room temperature, or 295 Kelvin. “We had roughly a factor of 2 difference in the resistivity between the 001 oriented tungsten and 110 oriented tungsten,” Gall said, but they found considerably smaller resistivity in the W(011) layers.

Although the measured anisotropic resistance effect was in good agreement with what they expected from calculations, the effective mean free path — the average distance electrons can move before scattering against a boundary — in the thin film experiments was much larger than the theoretical value for bulk tungsten.

“An electron travels through a wire on a diagonal, it hits a surface, gets scattered, and then continues traveling until it hits something else, maybe the other side of the wire or a lattice vibration,” Gall said. “But this model looks wrong for small wires.”

The experimenters believe this may be explained by quantum mechanical processes of the electrons that arise at these limited scales. Electrons may be simultaneously touching both sides of the wire or experiencing increased electron-phonon (lattice vibrations) coupling as the layer thickness decreases, phenomena that could affect the search for another metal to replace copper interconnects.

“The envisioned conductivity advantages of rhodium, iridium, and nickel may be smaller than predicted,” said Zheng. Findings like these will prove increasingly important as quantum mechanical scales become more commonplace for the demands of interconnects.

The research team is continuing to explore the anisotropic size effect in other metals with nonspherical Fermi surfaces, such as molybdenum. They found that the orientation of the surface relative to the layer orientation and transport direction is vital, as it determines the actual increase in resistivity at these reduced dimensions.

“The results presented in this paper clearly demonstrate that the correct choice of crystalline orientation has the potential to reduce nanowire resistance,” said Zheng. The importance of the work extends beyond current nanoelectronics to new and developing technologies, including transparent flexible conductors, thermoelectrics and memristors that can potentially store information. “It’s the problem that defines what you can do in the next technology,” Gall said.

From lifesaving smart headsets for truck drivers to gliding electric skateboards, five companies using MEMS and sensors will compete for audience votes during the Technology Showcase at the SEMI | MSIG MEMS & Sensors Executive Congress on November 1-2 in Napa Valley, Calif. As a featured event at the MEMS & Sensors Industry Group (MSIG) annual professional forum for executives from MEMS/sensors manufacturing and their end-user customers, the Technology Showcase highlights the newest and most unique MEMS/sensors-enabled applications in the industry.

“This year’s Technology Showcase finalists at the MEMS & Sensors Executive Congress are as fascinating as they are diverse,” said Frank Shemansky, CTO of SEMI | MSIG. “Imagine, for example, a MEMS-based switching element the width of a human hair, enabling RF switching that is 1,000 times faster and lasts 1,000 times longer than traditional mechanical switches. That is the kind of MEMS technology that could dramatically improve wireless applications, and it is just one of our Tech Showcase finalists ─  the others are equally compelling. The Tech Showcase is always a big draw at the Executive Congress because it gives attendees the chance to personally interact with the finalists’ demos to decide their vote for the winner – one of whom will be ‘crowned’ at the close of the conference.”

Tech Showcase Finalists

The LEIF eSnowboard by LEIF Technologies is the world’s first light electric vehicle that moves just like a snowboard. The LEIF brings to the pavement the smooth, sliding moves only found on a mountain or a wave — up to 23 mph and 15 miles per battery pack.

The Maven Co-Pilot by Maven Machines is the first smart headset for truck drivers. Employing MEMS, sensor fusion, wearable technology, machine intelligence and mobile-cloud architecture, the Maven Co-Pilot monitors drivers’ fatigue and distraction levels 50 times per second to provide accurate instantaneous early warnings to both drivers and fleet managers.

Menlo Digital-Micro-Switch Technology by Menlo Micro demonstrates fundamental materials’ advancements that improve the size, speed, power handling and reliability of MEMS switches. Smaller than the width of a human hair, Menlo Micro’s switching elements are so small that hundreds of them fit in a space smaller than 10mm2. Menlo Micro switches operate 1,000x faster than traditional mechanical switches — in a few microseconds rather than milliseconds. Their scalable architecture allows the handling of 100s of volts and 10s of amps without arcing. Menlo Micro’s devices last 1,000x longer than traditional mechanical switches, supporting billions of cycles without performance degradation.

The Berries Smart Sensor series by eLichens are patented autonomous non-dispersive infrared (NDIR) gas sensors offered in a 2 x 2 x 1cm package. These sensors integrate a dual-channel feature for a calibration-free long-life cycle. The miniaturized optical gas sensor is a complete system in package (SIP) integrating a proprietary infrared MEMS emitter and detectors, a highly efficient patented optical sampling chamber, and signal processing. The Berries series address the demanding requirements of the gas-sensing industries, where accuracy, auto-calibration and low power consumption are essential for new generations of gas- and air-detection products.

Coupled Time Domain Simulation for MEMS Sensors and System Integration by PZFlex lets engineers model and simulate a wide range of physics in new MEMS areas such as piezoelectric micromachined ultrasonic transducers (PMUTs) for fingerprint sensing. Engineers can conduct large-scale time-domain finite element analysis (FEA) simulation using PZFlex to gain insights into discrete device performance, device array performance, and full system performance for a PMUT fingerprint sensor embedded within a smartphone touch-display stackup.

MEMS & Sensors Executive Congress 2017 will take place November 1-2 at the Silverado Resort and Spa in Napa Valley, Calif. For more information, please contact SEMI via email: [email protected] or visit: www.semi.org/en/mems-sensors-executive-congress-2017.

IC Insights recently released its September Update to The McClean Report.  This 32-page Update included a detailed look at the pure-play foundry market.  Shown below is an excerpt from the Update.

With the rise of fabless IC companies in China, demand for foundry services in that country has also increased.  Figure 1 shows IC Insights’ listing of the top pure-play foundries and their sales to China in 2016 and a forecast for 2017.  In total, pure-play foundry sales in China are expected to jump by 16% this year to about $7.0 billion, more than double the rate of increase for the total pure-play foundry market.  As shown, only about 10% of TSMC’s sales are forecast to go into China in 2017, yet the company is expected to hold the largest share of the China foundry market this year with a 46% share, up two percentage points from 2016.

Figure 1

Figure 1

The Chinese foundry market represented 11% of the total pure-play foundry market in 2015, 12% in 2016, and is forecast to hold a 13% share this year.  As a result of this growth, most pure-play foundries have made plans to locate or expand IC production in mainland China over the next few years. TSMC, GlobalFoundries, UMC, Powerchip, and, most recently, TowerJazz have announced plans to boost their China-based wafer fabrication production.  Most of these new China-based foundry wafer fabs are scheduled to come online in late 2017 or in 2018.  UMC began 40nm production at its 300mm joint venture China fab in November of 2016 and the company is planning to introduce 28nm technology into the fab in the second half of this year with additional expansion plans to come through the end of the decade.

It is well known that China is striving to develop an indigenous semiconductor industry but gaining access to the manufacturing technology has become increasingly difficult.  As a result, many China IC companies and government entities have structured joint ventures or partnerships with foundry companies in order to access leading manufacturing technology.  The partnerships give Chinese companies much needed access to production capacity using first-rate manufacturing technology and provide the foundries with an ongoing market presence and revenue stream within China.

Examples of pure-play foundries that are working to set up new manufacturing plants in China include,

•    UMC is working with Fujian Jin Hua IC Company to construct a 300mm wafer fab in Fujian, China to manufacture DRAM using 32nm process technology developed by UMC.

•    GlobalFoundries joined with the Chengdu Government in 1Q17 to begin building a 300mm wafer fab that will manufacture ICs using mainstream 130nm and 180nm processes.  Completion is set for early 2018.

•    TSMC started construction on a wholly owned $3 billion fab in Nanjing, China that will serve as a foundry that manufactures ICs using 16nm technology.  Production is scheduled to begin in 2H18.

•    TowerJazz signed an agreement with Tacoma Semiconductor to construct a 200mm wafer fab, also in Nanjing, China.  TowerJazz will have access to 50% of the capacity.  Tacoma is responsible for the entire investment of the project.

Advanced Linear Devices Inc. (ALD), a designer of analog semiconductors, today announced a zero-gate threshold voltage EPAD P-Channel MOSFET Array launching the industry’s first precision sub-threshold circuit. The MOSFET currently has the industry’s lowest operating voltage of 0.2 Volt (V) and current of less than one nano amp (nA). These chips enable the operating regions required for the next generations of development in energy harvesting, Internet of Things (IoT) sensors applications.

The ALD310700A/ALD310700 quad zero threshold MOSFET is intended for the development of small signal precision applications utilizing 0.00V Zero Threshold Voltage. The circuit is ideal for designs requiring very low operating voltages of < +0.5V power supplies. Allowing circuits to operate in the subthreshold region for the first time ever, expands the MOSFET’s operating range into never-before achieved signal levels.

The new MOSFET simplifies circuit biasing schemes and reduces component counts while providing greater precision and sensitivity of sensor applications for IoT engineers. The P-Channel MOSFET can work in conjunction with ALD N-Channel Zero Threshold MOSFET devices in matched sensor applications. The ALD310700A/ALD310700 is the P-channel version of the popular ALD110800A/ALD110800 Precision Zero Threshold N-channel device. Together, these two MOSFET series deliver complementary precision performance. These complementary paired devices enable the design of 0.5% precision current mirrors, current sources, and circuits referenced to power or ground sources including differential amplifier input stages, transmission gates and multiplexers.

Notable device features

  •     Precision offset voltages (VOS): 2mV max.; 10mV max.;
  •     Low minimum operating voltage of less than 0.2V;
  •     Ultra-low minimum operating current of less than 1nA:
  •     Matched and tracked temperature characteristics.

“These devices operate at a point with 100 times lower power than comparable MOSFET arrays. More importantly they enable the next generation of applications at power levels and precision that were impossible until now,” said Robert Chao, President, and Founder, Advanced Linear Devices Inc. “These arrays offer circuit designers working on IoT nodes that require matched sensor activity a method to collect power from supercapacitors or deep cycle batteries.”

As an example, some potential energy harvesting sources, such as thermal electric generators that yield just 0.2V, produce such low levels of energy that they are barely useful for driving power in electronic circuitry. The ALD P-Channel Zero-Threshold (VGS(th)=0.00) EPAD MOSFET arrays can be coupled with a low voltage step-up converter to give low-level power sources a greater range as an energy harvesting source.

This device is available in a quad version and is a member of the EPAD® Matched Pair MOSFET Family. The parts can be ordered directly from ALD or DigiKey and Mouser. Prices start at $2.00 at 100 pieces.

The Semiconductor Industry Association (SIA) today announced worldwide sales of semiconductors reached $35.0 billion for the month of August 2017, an increase of 23.9 percent compared to the August 2016 total of $28.2 billion and 4.0 percent more than the July 2017 total of $33.6 billion. All major regional markets posted both year-to-year and month-to-month increases in August, and the Americas market led the way with growth of 39.0 percent year-to-year and 8.8 percent month-to-month. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average.

“Global semiconductor sales were up significantly in August, increasing year-to-year for the thirteenth consecutive month and reaching $35 billion for the first time,” said John Neuffer, president and CEO, Semiconductor Industry Association. “Sales in August increased across the board, with every major regional market and semiconductor product category posting gains on a month-to-month and year-to-year basis. Memory products continue be a major driver of overall market growth, but sales were up even without memory in August.”

Year-to-year sales increased in the Americas (39.0 percent), China (23.3 percent), Asia Pacific/All Other (19.5 percent), Europe (18.8 percent), and Japan (14.3 percent). Month-to-month sales increased in the Americas (8.8 percent), China (3.7 percent), Japan (2.8 percent), Asia Pacific/All Other (2.2 percent), and Europe (0.6 percent).

“With about half of global market share, the U.S. semiconductor industry is the worldwide leader, but U.S. companies face intense global competition,” said Neuffer. “To allow our industry to continue to grow and innovate here at home, policymakers in Washington should enact corporate tax reform that makes the U.S. tax system more competitive with other countries. The corporate tax reform framework released last week by leaders in Congress and the Trump Administration is an important step forward. We look forward to working with policymakers to enact corporate tax reform that strengthens our industry and the U.S. economy.”

Aug 2017

Billions

Month-to-Month Sales                              

Market

Last Month

Current Month

% Change

Americas

6.94

7.55

8.8%

Europe

3.20

3.22

0.6%

Japan

3.04

3.13

2.8%

China

10.68

11.08

3.7%

Asia Pacific/All Other

9.77

9.98

2.2%

Total

33.63

34.96

4.0%

Year-to-Year Sales                         

Market

Last Year

Current Month

% Change

Americas

5.43

7.55

39.0%

Europe

2.71

3.22

18.8%

Japan

2.73

3.13

14.3%

China

8.99

11.08

23.3%

Asia Pacific/All Other

8.35

9.98

19.5%

Total

28.22

34.96

23.9%

Three-Month-Moving Average Sales

Market

Mar/Apr/May

Jun/Jul/Aug

% Change

Americas

6.27

7.55

20.5%

Europe

3.11

3.22

3.8%

Japan

2.95

3.13

6.0%

China

10.25

11.08

8.1%

Asia Pacific/All Other

9.43

9.98

5.9%

Total

31.99

34.96

9.3%

In a flexible display, the backplane, frontplane, and any encapsulants are all made from flexible materials. To date, such displays have been used primarily because they are thinner, lighter, and more durable than comparable rigid displays, and to a lesser extent because they are conformable to rigid but non-flat surfaces in devices such as mobile phone handsets, automobile dashboards, and appliance control panels.

In 2017, key flexible display components achieved cost and performance parity with their rigid counterparts for the first time, thus removing a key market barrier and opening the door to rapid adoption in a variety of otherwise-rigid devices such as e-readers and wearables. Such displays may also be incorporated into truly flexible devices such as credit cards, shelving labels, and smart signage, and in the near future they may form the basis of rollable and foldable devices that define entirely new market categories.

According to a new report from Tractica, the four leading technologies in flexible displays are LED, LCD, OLED, and e-paper, and the main applications for these technologies are phones and tablets, wearables, shelving labels, signage, automotive dashboards, appliance control panels, TV and video displays, smart cards, e-writers, and e-readers. The market intelligence firm forecasts that flexible display shipments will increase from 169.9 million units in 2017 to 642.6 million units annually by 2022.

“The effect of flexible and conformable displays will be transformational,” says senior analyst Wil McCarthy. “They will literally change the appearance and function of our personal devices, our vehicles, our homes, and the built environment.”

Tractica’s report, “Flexible Displays”, examines the market trends and technology issues surrounding flexible displays and presents 6-year market forecasts, segmented by world region, for flexible display unit shipments, square meters, device pricing and revenue, and software applications during the period from 2017 through 2022. Flexible display applications are analyzed in depth, and the report also includes detailed profiles of 13 key industry players. An Executive Summary of the report is available for free download on the firm’s website.

A team of University of Wisconsin–Madison engineers has created the most functional flexible transistor in the world — and with it, a fast, simple and inexpensive fabrication process that’s easily scalable to the commercial level.

It’s an advance that could open the door to an increasingly interconnected world, enabling manufacturers to add “smart,” wireless capabilities to any number of large or small products or objects — like wearable sensors and computers for people and animals — that curve, bend, stretch and move.

Literal flexibility may bring the power of a new transistor developed at UW–Madison to digital devices that bend and move. PHOTO COURTESY OF JUNG-HUN SEO, UNIVERSITY AT BUFFALO, STATE UNIVERSITY OF NEW YORK

Literal flexibility may bring the power of a new transistor developed at UW–Madison to digital devices that bend and move. PHOTO COURTESY OF JUNG-HUN SEO, UNIVERSITY AT BUFFALO, STATE UNIVERSITY OF NEW YORK

Transistors are ubiquitous building blocks of modern electronics. The UW–Madison group’s advance is a twist on a two-decade-old industry standard: a BiCMOS (bipolar complementary metal oxide semiconductor) thin-film transistor, which combines two very different technologies — and speed, high current and low power dissipation in the form of heat and wasted energy — all on one surface.

As a result, these “mixed-signal” devices (with both analog and digital capabilities) deliver both brains and brawn and are the chip of choice for many of today’s portable electronic devices, including cellphones.

“The industry standard is very good,” says Zhenqiang (Jack) Ma, the Lynn H. Matthias Professor and Vilas Distinguished Achievement Professor in electrical and computer engineering at UW–Madison. “Now we can do the same things with our transistor — but it can bend.”

Ma is a world leader in high-frequency flexible electronics. He and his collaborators described their advance in the inaugural issue of the journal npj Flexible Electronics, published Sept. 27.

Making traditional BiCMOS flexible electronics is difficult, in part because the process takes several months and requires a multitude of delicate, high-temperature steps. Even a minor variation in temperature at any point could ruin all of the previous steps.

Ma and his collaborators fabricated their flexible electronics on a single-crystal silicon nanomembrane on a single bendable piece of plastic. The secret to their success is their unique process, which eliminates many steps and slashes both the time and cost of fabricating the transistors.

“In industry, they need to finish these in three months,” he says. “We finished it in a week.”

He says his group’s much simpler high-temperature process can scale to industry-level production right away.

“The key is that parameters are important,” he says. “One high-temperature step fixes everything — like glue. Now, we have more powerful mixed-signal tools. Basically, the idea is for flexible electronics to expand with this. The platform is getting bigger.”

His collaborators include Jung-Hun Seo of the University at Buffalo, State University of New York; Kan Zhang of UW–Madison; and Weidong Zhou of the University of Texas at Arlington.

A sea of spinning electrons


October 3, 2017

Picture two schools of fish swimming in clockwise and counterclockwise circles. It’s enough to make your head spin, and now scientists at Rutgers University-New Brunswick and the University of Florida have discovered the “chiral spin mode” – a sea of electrons spinning in opposing circles.

“We discovered a new collective spin mode that can be used to transport energy or information with very little energy dissipation, and it can be a platform for building novel electronic devices such as computers and processors,” said Girsh Blumberg, senior author of the study and a professor in the Department of Physics and Astronomy in Rutgers’ School of Arts and Sciences.

Collective chiral spin modes are propagating waves of electron spins that do not carry a charge current but modify the “spinning” directions of electrons. “Chiral” refers to entities, like your right and left hands, that are matching but asymmetrical and can’t be superimposed on their mirror image.

The study, led by Hsiang-Hsi (Sean) Kung, a graduate student in Blumberg’s Rutgers Laser Spectroscopy Lab, was published in Physical Review Letters. Kung used a custom-made, ultra-sensitive spectrometer to study a prototypical 3D topological insulator. A microscopic theoretical model that predicts the energy and temperature evolution of the chiral spin mode was developed by Saurabh Maiti and Professor Dmitrii Maslov at the University of Florida, strongly substantiating the experimental observation.

The blue and red cones show the energy and momentum of surface electrons in a 3D topological insulator. The spin structure is shown in the blue and red arrows at the top and bottom, respectively. Light promotes electrons from the blue cone into the red cone, with the spin direction flipping. The orderly spinning leads to the chiral spin mode observed in this study. Credit: Hsiang-Hsi (Sean) Kung/Rutgers University-New Brunswick

The blue and red cones show the energy and momentum of surface electrons in a 3D topological insulator. The spin structure is shown in the blue and red arrows at the top and bottom, respectively. Light promotes electrons from the blue cone into the red cone, with the spin direction flipping. The orderly spinning leads to the chiral spin mode observed in this study.
Credit: Hsiang-Hsi (Sean) Kung/Rutgers University-New Brunswick

In a vacuum, electrons are simple, boring elementary particles. But in solids, the collective behavior of many electrons interacting with each other and the underlying platform may result in phenomena that lead to new applications in superconductivity, magnetism and piezoelectricity (voltage generated via materials placed under pressure), to name a few. Condensed matter science, which focuses on solids, liquids and other concentrated forms of matter, seeks to reveal new phenomena in new materials.

Silicon-based electronics, such as computer chips and computers, are one of the most important inventions in human history. But silicon leads to significant energy loss when scaled down. One alternative is to harness the spins of electrons to transport information through extremely thin wires, which in theory would slash energy loss.

The newly discovered “chiral spin mode” stems from the sea of electrons on the surface of “3D topological insulators.” These special insulators have nonmagnetic, insulating material with robust metallic surfaces, and the electrons are confined so they move only on 2D surfaces.

Most importantly, the electrons’ spinning axes are level and perpendicular to their velocity. Chiral spin modes emerge naturally from the surface of such insulating materials, but they were never observed before due to crystalline defects. The experimental observation in the current study was made possible following the development of ultra-clean crystals by Rutgers doctoral student Xueyun Wang and Board of Governors Professor Sang-Wook Cheong in the Rutgers Center for Emergent Materials.

The discovery paves new paths for building next generation low-loss electronic devices.