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IBM today announced a significant milestone in the development of silicon photonics technology, which enables silicon chips to use pulses of light instead of electrical signals over wires to move data at rapid speeds and longer distances in future computing systems.

For the first time, IBM engineers have designed and tested a fully integrated wavelength multiplexed silicon photonics chip, which will soon enable manufacturing of 100 Gb/s optical transceivers. This will allow datacenters to offer greater data rates and bandwidth for cloud computing and Big Data applications.

“Making silicon photonics technology ready for widespread commercial use will help the semiconductor industry keep pace with ever-growing demands in computing power driven by Big Data and cloud services,” said Arvind Krishna, senior vice president and director of IBM Research. “Just as fiber optics revolutionized the telecommunications industry by speeding up the flow of data — bringing enormous benefits to consumers — we’re excited about the potential of replacing electric signals with pulses of light. This technology is designed to make future computing systems faster and more energy efficient, while enabling customers to capture insights from Big Data in real time.”

Silicon photonics uses tiny optical components to send light pulses to transfer large volumes of data at very high speed between computer chips in servers, large datacenters, and supercomputers, overcoming the limitations of congested data traffic and high-cost traditional interconnects. IBM’s breakthrough enables the integration of different optical components side-by-side with electrical circuits on a single silicon chip using sub-100nm semiconductor technology.

IBM’s silicon photonics chips uses four distinct colors of light travelling within an optical fiber, rather than traditional copper wiring, to transmit data in and around a computing system. In just one second, this new transceiver is estimated to be capable of digitally sharing 63 million tweets or six million images, or downloading an entire high-definition digital movie in just two seconds.

The technology industry is entering a new era of computing that requires IT systems and cloud computing services to process and analyze huge volumes of Big Data in real time, both within datacenters and particularly between cloud computing services. This requires that data be rapidly moved between system components without congestion. Silicon photonics greatly reduces data bottlenecks inside of systems and between computing components, improving response times and delivering faster insights from Big Data.

IBM’s new CMOS Integrated Nano-Photonics Technology will provide a cost-effective silicon photonics solution by combining the vital optical and electrical components, as well as structures enabling fiber packaging, on a single silicon chip. Manufacturing makes use of standard fabrication processes at a silicon chip foundry, making this technology ready for commercialization.

Silicon photonics technology leverages the unique properties of optical communications, which include transmission of high-speed data over kilometer-scale distances, and the ability to overlay multiple colors of light within a single optical fiber to multiply the data volume carried, all while maintaining low power consumption. These characteristics combine to enable rapid movement of data between computer chips and racks within servers, supercomputers, and large datacenters, in order to alleviate the limitations of congested data traffic produced by contemporary interconnect technologies.

Silicon photonics will transform future datacenters

By moving information via pulses of light through optical fibers, optical interconnects are an integral part of contemporary computing systems and next generation datacenters. Computer hardware components, whether a few centimeters or a few kilometers apart, can seamlessly and efficiently communicate with each other at high speeds using such interconnects. This disaggregated and flexible design of datacenters will help reduce the cost of space and energy, while increasing performance and analysis capabilities for users ranging from social media companies to financial services to universities.

Most of the optical interconnect solutions employed within datacenters as of today are based upon vertical cavity surface emitting laser (VCSEL) technology, where the optical signals are transported via multimode optical fiber. Demands for increased distance and data rate between ports, due to cloud services for example, are driving the development of cost-effective single-mode optical interconnect technologies, which can overcome the bandwidth-distance limitations inherent to multimode VCSEL links.

IBM’s CMOS Integrated Nano-Photonics Technology provides an economical solution to extend the reach and data rates of optical links. The essential parts of an optical transceiver, both electrical and optical, can be combined monolithically on one silicon chip, and are designed to work with with standard silicon chip manufacturing processes.

IBM engineers in New York and Zurich, Switzerland and IBM Systems Unit have demonstrated a reference design targeting datacenter interconnects with a range up to two kilometers. This chip demonstrates transmission and reception of high-speed data using four laser “colors,” each operating as an independent 25 Gb/s optical channel. Within a full transceiver design, these four channels can be wavelength multiplexed on-chip to provide 100 Gb/s aggregate bandwidth over a duplex single-mode fiber, thus minimizing the cost of the installed fiber plant within the datacenter.

Further details will be presented by IBM at the 2015 Conference on Lasers and Electro Optics (May 10-15) in San Jose, California, during the invited presentation entitled “Demonstration of Error Free Operation Up To 32 Gb/s From a CMOS Integrated Monolithic Nano-Photonic Transmitter,” by Douglas M. Gill, Chi Xiong, Jonathan E. Proesel, Jessie C. Rosenberg, Jason Orcutt, Marwan Khater, John Ellis-Monaghan, Doris Viens, Yurii Vlasov, Wilfried Haensch, and William M. J. Green.

IBM Research has been leading the development of silicon photonics for more than a decade, announcing a series of technology milestones beginning in 2006. Silicon photonics is among the efforts of IBM’s $3 billion investment to push the limits of chip technology to meet the emerging demands of cloud and Big Data systems.

By combining 3D holographic lithography and 2D photolithography, researchers from the University of Illinois at Urbana-Champaign have demonstrated a high-performance 3D microbattery suitable for large-scale on-chip integration with microelectronic devices.

“This 3D microbattery has exceptional performance and scalability, and we think it will be of importance for many applications,” explained Paul Braun, a professor of materials science and engineering at Illinois. “Micro-scale devices typically utilize power supplied off-chip because of difficulties in miniaturizing energy storage technologies. A miniaturized high-energy and high-power on-chip battery would be highly desirable for applications including autonomous microscale actuators, distributed wireless sensors and transmitters, monitors, and portable and implantable medical devices.”

CREDIT: University of Illinois

CREDIT: University of Illinois

“Due to the complexity of 3D electrodes, it is generally difficult to realize such batteries, let alone the possibility of on-chip integration and scaling. In this project, we developed an effective method to make high-performance 3D lithium-ion microbatteries using processes that are highly compatible with the fabrication of microelectronics,” stated Hailong Ning, a graduate student in the Department of Materials Science and Engineering and first author of the article, “Holographic Patterning of High Performance on-chip 3D Lithium-ion Microbatteries,” appearing in Proceedings of the National Academy of Sciences.

“We utilized 3D holographic lithography to define the interior structure of electrodes and 2D photolithography to create the desired electrode shape.” Ning added. “This work merges important concepts in fabrication, characterization, and modeling, showing that the energy and power of the microbattery are strongly related to the structural parameters of the electrodes such as size, shape, surface area, porosity, and tortuosity. A significant strength of this new method is that these parameters can be easily controlled during lithography steps, which offers unique flexibility for designing next-generation on-chip energy storage devices.”

Enabled by a 3D holographic patterning technique–where multiple optical beams interfere inside the photoresist creating a desirable 3D structure–the battery possesses well-defined, periodically structured porous electrodes, that facilitates the fast transports of electrons and ions inside the battery, offering supercapacitor-like power.

“Although accurate control on the interfering optical beams is required to construct 3D holographic lithography, recent advances have significantly simplified the required optics, enabling creation of structures via a single incident beam and standard photoresist processing. This makes it highly scalable and compatible with microfabrication,” stated John Rogers, a professor of materials science and engineering, who has worked with Braun and his team to develop the technology.

“Micro-engineered battery architectures, combined with high energy material such as tin, offer exciting new battery features including high energy capacity and good cycle lives, which provide the ability to power practical devices,” stated William King, a professor of mechanical science and engineering, who is a co-author of this work.

Researchers at the University of Rochester have shown that defects on an atomically thin semiconductor can produce light-emitting quantum dots. The quantum dots serve as a source of single photons and could be useful for the integration of quantum photonics with solid-state electronics – a combination known as integrated photonics.

Scientists have become interested in integrated solid-state devices for quantum information processing uses. Quantum dots in atomically thin semiconductors could not only provide a framework to explore the fundamental physics of how they interact, but also enable nanophotonics applications, the researchers say.

Quantum dots are often referred to as artificial atoms. They are artificially engineered or naturally occurring defects in solids that are being studied for a wide range of applications. Nick Vamivakas, assistant professor of optics at the University of Rochester and senior author on the paper, adds that atomically thin, 2D materials, such as graphene, have also generated interest among scientists who want to explore their potential for optoelectronics. However, until now, optically active quantum dots have not been observed in 2D materials.

In a paper published in Nature Nanotechnology this week, the Rochester researchers show how tungsten diselenide (WSe2) can be fashioned into an atomically thin semiconductor that serves as a platform for solid-state quantum dots. Perhaps most importantly the defects that create the dots do not inhibit the electrical or optical performance of the semiconductor and they can be controlled by applying electric and magnetic fields.

Vamivakas explains that the brightness of the quantum dot emission can be controlled by applying the voltage. He adds that the next step is to use voltage to “tune the color” of the emitted photons, which can make it possible to integrate these quantum dots with nanophotonic devices.

A key advantage is how much easier it is to create quantum dots in atomically thin tungsten diselenide compared to producing quantum dots in more traditional materials like indium arsenide.

“We start with a black crystal and then we peel layers of it off until we have an extremely thin later left, an atomically thin sheet of tungsten diselenide,” said Vamivakas.

The researchers take two of these atomically thin sheets and lay one over the other one. At the point where they overlap, a quantum dot is created. The overlap creates a defect in the otherwise smooth 2D sheet of semiconductor material. The extremely thin semiconductors are much easier to integrate with other electronics.

The quantum dots in tungsten diselenide also possess an intrinsic quantum degree of freedom – the electron spin. This is a desirable property as the spin can both act as a store of quantum information as well as provide a probe of the local quantum dot environment.

“What makes tungsten diselenide extremely versatile is that the color of the single photons emitted by the quantum dots is correlated with the quantum dot spin,” said first author Chitraleema Chakraborty. Chakraborty added that the ease with which the spins and photons interact with one another should make these systems ideal for quantum information applications as well as nanoscale metrology.

Achieving precise registration accuracy is a factor of two related variables: web tension and transport velocity.

BY BIPIN SEN, Bosch Rexroth, Hoffman Estates, IL

One of the brightest developments in electronics is Organic Light Emitting Diode (OLED) TVs, which are attracting consumers with their eye-popping colors and super- thin designs. Unlike the components found in traditional flat-screen display technology, OLEDs use thin, flexible sheets of material that emit their own light and are produced using a technique similar to inkjet or sheet-feed printing.

Introduced to the consumer market only a few years ago, OLEDs are still relatively costly to manufacture in large sizes due to limitations in both shadow-mask deposition methods, and in newer laser annealing and inkjet printing techniques. To scale up large area display production economically, printed electronics manufacturers are seeing the benefits of another production method — namely, digital roll-to-roll web processing.

Like an inkjet printer deposits ink on sheets of paper, a digital roll-to-roll press patterns thin-film transistors and other devices directly onto large organic, flexible substrates. But unlike slower sheet-fed digital printing, the substrate in a roll-to-roll press is supplied from an infeed reel through the printing section onto an outfeed reel in one continuous inline web. An array of piezo- electric printheads deposit the ink — comprised of a conductive organic solution — on the substrate at precise locations. In roll-to-roll web processing, electroluminescent materials or other microcrys- talline layers are deposited on substrate at slower speeds, on the order of 10 to 100 feet (3 to 30 meters) per minute.

The speed of the roll-to-roll process reduces the cost of fabrication dramatically—but several challenges must be overcome to make it pay off.

Fast speeds create big challenges

Similar to how Sunday newspaper comics require precise color registration to keep images from blurring, printed electronics require far tighter registration. Tolerances for applications such as Thin-Film Transistors (TFTs) or OLEDs require registration smaller than 10 microns. High-speed, high-resolution cameras measure registration accuracy and provide input to the control system. To ensure that degree of accuracy, precise web tension control is required.

Achieving precise registration accuracy is a factor of two related variables: web tension and transport velocity.

Web transport control ensures proper uniform tension on the substrate web as it travels through the process. Because the substrate changes properties in response to force loading, changes in tension affect the stability of deposited materials. Substrate expansion causes cracks, broken traces, short circuiting and layer delamination. Changes in web velocity in the print zone affect registration, thickness and resolution of fine lines.

As the web travels downstream, constant tension must be maintained in each tension zone, which
is defined as an isolated area in a machine where constant tension must be maintained appropriate to the process being performed in that area. A roll- to-roll press has several tension zones. Problems occur when a change is made in one tension zone and no change is needed in other areas. When tension control is coupled between all zones, a change in one creates a cascade of changes in others, impacting the stability of the entire web.

FIGURE 1 shows how instability affects a web traveling at five meters per second with two successive tension controllers for two tension zones. A command for a step change tension reduction is sent to the green zone controllers.

FIGURE 1. Tension instability.

FIGURE 1. Tension instability.

No change is required in the upstream blue zone. But because the web is continuous, the tension disturbance is carried back to the blue zone, which causes the blue controller to compensate. In turn, this change affects the downstream green zone, sending jitter back to the blue zone. This back and forth jitter takes about 85 seconds to settle down. The web tension finally stabilizes in about 90 seconds. During that time, the machine is yielding waste product.

The challenge of tension adjustment

In an ideal world, web instability would never occur because tension adjustment would never be needed. But tension adjustment is necessary due to several mechanical factors:

  • Oscillations caused by mechanical misalignments
  • Differing inertial response (lag) of mechanical elements during web acceleration
  • Out-of-round unwind and tension rolls
  • Slipping through nip rolls
  • Over aggressive web-guide correction

Several technical process and control issues also affect tension: tension set point changes, phase offset on driven rolls, tension bleed from one zone to another, and, of course, thermal effect (contraction/expansion) as the substrate passes through various processes.

The factors requiring tension adjustment cannot all be eliminated. Variance in any one factor in a zone necessitates changes in tension control and web speed. Consequently, with coupled tension zone control, jitter is inevitable in a continuous web where the controllers cause a feedback loop.

The benefits of decoupled controllers

There is a solution: Decouple each tension zone, allowing each controller to operate independently.
This has been accomplished in digital printing applications using Bosch Rexroth controllers incor- porating a unique tension decoupling function block. As the name implies, the function block allows tension control for each zone to operate independently. As a result, tension changes can be isolated in one zone without affecting tension change in other areas.

The result can be seen in FIGURE 2. In this example, the press uses two successive controllers. But now the step change signaled by the green section controller doesn’t create a cascade effect upstream. Along with decoupling to prevent feedback, the Rexroth controller initiates a response to step reduction in tension control in one-fourth the time compared to typical controllers.

FIGURE 2. Improved tension control.

FIGURE 2. Improved tension control.

With the Rexroth solution, tension can be controlled for up to eight axes. One or multiple points can be selected to be left uncontrolled. At the selected axis, line speed is held constant. At a standstill, web tension can be maintained. In fact, Rexroth multi-axis tension control increases stand-still web tension accuracy by a factor of two to four. Achieving the desired standstill web tension is also much faster. Without decoupling, a setpoint can be achieved in 13-14 seconds; with decoupling, it takes three to four seconds.

During acceleration, tension control decoupling ensures the web is stable as soon as full production speed is reached, compared to a delay of five seconds or longer with coupled control. And when tension setpoint changes occur during runtime, the transient response with decoupling takes about one second, compared to about four seconds with coupled control.

Not unlike digital printing, the adoption of roll-to-roll web printing will accelerate as the technology demonstrates its ability to provide high accuracy at high speeds.

The promising new material molybdenum disulfide (MoS2) has an inherent issue that’s steeped in irony. The material’s greatest asset–its monolayer thickness–is also its biggest challenge.

Monolayer MoS2’s ultra-thin structure is strong, lightweight, and flexible, making it a good candidate for many applications, such as high-performance, flexible electronics. Such a thin semiconducting material, however, has very little interaction with light, limiting the material’s use in light emitting and absorbing applications.

“The problem with these materials is that they are just one monolayer thick,” said Koray Aydin, assistant professor of electrical engineering and computer science at Northwestern University’s McCormick School of Engineering. “So the amount of material that is available for light emission or light absorption is very limited. In order to use these materials for practical photonic and optoelectric applications, we needed to increase their interactions with light.”

Aydin and his team tackled this problem by combining nanotechnology, materials science, and plasmonics, the study of the interactions between light and metal. The team designed and fabricated a series of silver nanodiscs and arranged them in a periodic fashion on top of a sheet of MoS2. Not only did they find that the nanodiscs enhanced light emission, but they determined the specific diameter of the most successful disc, which is 130 nanometers.

“We have known that these plasmonic nanostructures have the ability to attract and trap light in a small volume,” said Serkan Butun, a postdoctoral researcher in Aydin’s lab. “Now we’ve shown that placing silver nanodiscs over the material results in twelve times more light emission.”

The use of the nanostructures–as opposed to using a continuous film to cover the MoS2–allows the material to retain its flexible nature and natural mechanical properties.

Supported by Northwestern’s Materials Research Science and Engineering Center and the Institute for Sustainability and Energy at Northwestern, the research is described in the March 2015 online issue of NanoLetters. Butun is first author of the paper. Sefaatiin Tongay, assistant professor of materials science and engineering at Arizona State University, provided the large-area monolayer MoS2 material used in the study.

With enhanced light emission properties, MoS2 could be a good candidate for light emitting diode technologies. The team’s next step is to use the same strategy for increasing the material’s light absorption abilities to create a better material for solar cells and photodetectors.

“This is a huge step, but it’s not the end of the story,” Aydin said. “There might be ways to enhance light emission even further. But, so far, we have successfully shown that it’s indeed possible to increase light emission from a very thin material.”

University of Washington scientists have built a new nanometer-sized laser — using the thinnest semiconductor available today — that is energy efficient, easy to build and compatible with existing electronics.

Lasers play essential roles in countless technologies, from medical therapies to metal cutters to electronic gadgets. But to meet modern needs in computation, communications, imaging and sensing, scientists are striving to create ever-smaller laser systems that also consume less energy.

The ultra-thin semiconductor, which is about 100,000 times thinner than a human hair, stretches across the top of the photonic cavity. Credit: University of Washington

The ultra-thin semiconductor, which is about 100,000 times thinner than a human hair, stretches across the top of the photonic cavity. Credit:
University of Washington

The UW nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as the “gain material” that emits light. The technology is described in a paper published in the March 16 online edition of Nature.

“This is a recently discovered, new type of semiconductor which is very thin and emits light efficiently,” said Sanfeng Wu, lead author and a UW doctoral candidate in physics. “Researchers are making transistors, light-emitting diodes, and solar cells based on this material because of its properties. And now, nanolasers.”

Nanolasers — which are so small they can’t be seen with the eye — have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems. But nanolasers so far haven’t strayed far from the research lab.

Other nanolaser designs use gain materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electrical circuits and computing technologies.

The UW version, instead, uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultrathin nature of the semiconductor — made from a single layer of a tungsten-based molecule — yields efficient coordination between the two key components of the laser.

The UW nanolaser requires only 27 nanowatts to kickstart its beam, which means it is very energy efficient.

Other advantages of the UW team’s nanolaser are that it can be easily fabricated, and it can potentially work with silicon components common in modern electronics. Using a separate atomic sheet as the gain material offers versatility and the opportunity to more easily manipulate its properties.

“You can think of it as the difference between a cell phone where the SIM card is embedded into the phone versus one that’s removable,” said co-author Arka Majumdar, UW assistant professor of electrical engineering and of physics.

“When you’re working with other materials, your gain medium is embedded and you can’t change it. In our nanolasers, you can take the monolayer out or put it back, and it’s much easier to change around,” he said.

The researchers hope this and other recent innovations will enable them to produce an electrically-driven nanolaser that could open the door to using light, rather than electrons, to transfer information between computer chips and boards.

The current process can cause systems to overheat and wastes power, so companies such as Facebook, Oracle, HP, Google and Intel with massive data centers are keenly interested in more energy-efficient solutions.

Using photons rather than electrons to transfer that information would consume less energy and could enable next-generation computing that breaks current bandwidth and power limitations. The recently proven UW nanolaser technology is one step toward making optical computing and short distance optical communication a reality.

“We all want to make devices run faster with less energy consumption, so we need new technologies,” said co-author Xiaodong Xu, UW associate professor of materials science and engineering and of physics. “The real innovation in this new approach of ours, compared to the old nanolasers, is that we’re able to have scalability and more controls.”

Still, there’s more work to be done in the near future, Xu said. Next steps include investigating photon statistics to establish the coherent properties of the laser’s light.

Cambridge Nanotherm has published results of a round of testing of several thermal PCB materials intended for use in LEDs, including its Nanoceramic thermal management substrates for LEDs. The tests were conducted by The LIA Laboratories (part of The LIA – Europe’s largest lighting trade association) and showed Cambridge Nanotherm’s thermal management technology outperforming all the thermal management substrates tested in terms of its thermal conductivity.

The LIA Laboratories test used 4 x 50 watt Intelligent LED Solutions Oslon 16+ PowerClusters mounted on four different MCPCB (Metal Clad PCB) substrates from leading manufacturers including Nanotherm LC. The substrates were attached with a TIM to a Fischer Elektronik LA 7/150 fan-cooled heat sink (thermal resistance: 0.075°C/W). A precision EA-PS 2084-10B (0-10A; 0-84V) laboratory power supply was used to drive the LEDs at constant current. Thermocouples measured the cluster and heat sink temperature at multiple locations. A calibrated integrating sphere measured the Lumens output.

With a drive current of 1,000mA running through the LEDs, Nanotherm LC ran a massive 13.6°C (30%) cooler than the generic Chinese MCPCB used as a ‘control’ board. Even compared to the closest high-performance board Nanotherm LC ran 2.4°C (5 percent) cooler.

The tests also examined how much extra luminosity could be achieved on Nanotherm LC within a given temperature envelope, compared to the nearest competitor. At 1,000mA drive current, LEDs on the closest high-performance board ran at 39.7°C and delivered a light output of 4760 Lumens. When LEDs on Nanotherm LC were run up to this exact same temperature of 39.7°C, the LEDs were able to handle a drive current of 1,350mA and produced a luminosity of 5896 Lumens. In effect, at the same temperature as the competitor board, Nanotherm produced a 23.8 percent increase in brightness. Applied to the real world this means Nanotherm LC provides a clear path for manufacturers to substantially reduce the number of LED dies used in any given design whilst maintaining the brightness.

“The figures don’t lie,” commented Ralph Weir, CEO, Cambridge Nanotherm. “The results show Cambridge Nanotherm’s LC substrate outperforming every other MCPCB that was tested, including what we believe to be the current market leader.”

“Our results demonstrate two distinct possibilities, the ability to reduce overall system temperatures, or to run LEDs at a greater luminosity within a given temperature envelope. Both should have LED manufacturers very excited. These tests demonstrate comprehensively that our substrates can be used to drive down LED costs through die count reduction while maintaining product efficiency and lifetimes. The ability to drive LEDs harder, cooler and brighter should help forge new application areas.”

“These results demonstrate yet again why Nanotherm materials are enjoying such success in the high-power LED market. We’re delighted that the LIA Laboratories, as a fully independent test house, has confirmed that they achieved a 23 percent increase in brightness from the same LEDs – just by using Nanotherm materials rather than the more expensive options from the most respected “big brand” MCPCB suppliers.”

Under continuous drive at the same high current of 2,400mA, the test had to be stopped after a few minutes as even with this powerful heat sink all but Nanotherm exceeded 100°C  – the generic Chinese MCPCB was a staggering 47.2°C hotter. Even the best competitor exceeded 100°C, running 8.6°C hotter than the Nanotherm material. At this current Nanotherm’s substrate was the only one to keep the LEDs below 100°C.

Marktech Optoelectronics Corp. announces the addition of a PLCC-4 and miniature ceramic package to the 650nm and 850nm Point Source LED series. Point Source LEDs are designed to deliver precise and consistent performance in the most demanding applications such as high-speed optical encoders, linear positioning, optical switch and critical sensing applications. As miniaturization continues to be the focus of new product designs, small high reliability LED packaging will be needed to match performance.

Marktech Point Source LEDs are powered by a unique LED die that produces a well-defined pattern of light similar to a “point.” These die or chips in combination with high quality optical grade glass lenses produce an extremely narrow, near parallel radiation pattern. This unobstructed, radiated beam pattern is made possible by masking the die and relocating the topside electrode. By eliminating the “dark spot” typically associated with the center of conventional LEDs, the point source LED yields superior results in critical sensing applications.

Through-hole package options for this series include high reliability hermetically sealed TO-18 and TO-46 metal cans with a variety of lensing options which produce and array of viewing angles. Devices supplied without optics are manufactured with a flat glass window allowing the designer to utilize proprietary collimating or other application specific optics to take full advantage of the undistorted beam. Vincent C Forte, Marktech CTO said, “The Point Source LED is a suitable alternative to laser diodes in short distant applications offering increased temperature range capabilities and reduced risk of discharge due to ESD.”

Marktech ceramic package LED

Researchers at Aalto University, Finland have developed a new method to implement different types of nanowires side-by-side into a single array on a single substrate. The new technique makes it possible to use different semiconductor materials for the different types of nanowires.

‘We have succeeded in combining nanowires grown by the VLS (vapor-liquid-solid) and SAE (selective-area epitaxy) techniques onto the same platform. The difference compared with studies conducted previously on the same topic is that in the dual-type array the different materials do not grow in the same nanowire, but rather as separate wires on the same substrate’, says Docent Teppo Huhtio.

The research results were published in the Nano Letters journal on 5 February 2015.

Several applications 

The new fabrication process has many phases. First, gold nanoparticles are spread on a substrate. Next, the substrate is coated with silicon oxide, into which small holes are then patterned using electron beam lithography. In the first step of growth, (SAE), nanowires grow from where the holes are located, after which the silicon oxide is removed. In the second phase different types of nanowires are grown with the help of the gold nanoparticles (VLS). The researchers used metalorganic vapor phase epitaxy reactor in which the starting materials decompose at a high temperature, forming semiconductor compounds on the substrate.

“In this way we managed to combine two growth methods into the same process,” says doctoral candidate Joona-Pekko Kakko.

“We noticed in optical reflection measurements that light couples better to this kind of combination structure. For instance, a solar cell has less reflection and better absorption of light,” Huhtio adds.

In addition to solar cells and LEDs, the researchers also see good applications in thermoelectric generators. Further processing for component applications has already begun.

Nanowires are being intensely researched, because semiconductor components that are currently in use need to be made smaller and more cost-effective. The nanowires made out of semiconductor materials are typically 1-10 micrometres in length, with diameters of 5-100 nanometres.

The future of electronics could lie in a material from its past, as researchers from The Ohio State University work to turn germanium–the material of 1940s transistors–into a potential replacement for silicon.

At the American Association for the Advancement of Science meeting, assistant professor of chemistry Joshua Goldberger reported progress in developing a form of germanium called germanane.

In 2013, Goldberger’s lab at Ohio State became the first to succeed at creating one-atom-thick sheet of germanane–a sheet so thin, it can be thought of as two-dimensional. Since then, he and his team have been tinkering with the atomic bonds across the top and bottom of the sheet, and creating hybrid versions of the material that incorporate other atoms such as tin.

The goal is to make a material that not only transmits electrons 10 times faster than silicon, but is also better at absorbing and emitting light–a key feature for the advancement of efficient LEDs and lasers.

“We’ve found that by tuning the nature of these bonds, we can tune the electronic structure of the material. We can increase or decrease the energy it absorbs,” Goldberger said. “So potentially we could make a material that traverses the entire electromagnetic spectrum, or absorbs different colors, depending on those bonds.”

As they create the various forms of germanane, the researchers are trying to exploit traditional silicon manufacturing methods as much as possible, to make any advancements easily adoptable by industry.

Aside from these traditional semiconductor applications, there have been numerous predictions that a tin version of the material could conduct electricity with 100 percent efficiency at room temperature. The heavier tin atom allows the material to become a 2D “topological insulator,” which conducts electricity only at its edges., Goldberger explained. Such a material is predicted to occur only with specific bonds across the top and bottom surface, such as a hydroxide bond.

Goldberger’s lab has verified that this theoretical material can be chemically stable. His lab has created germanane with up to 9 percent tin atoms incorporated, and shown that tin atoms have strong preference to bond to hydroxide above and below the sheet. His group is currently developing routes towards preparing the pure tin 2D derivatives.