Tag Archives: letter-pulse-tech

Semiconductors N.V. (NASDAQ:NXPI) has expanded its cellular infrastructure portfolio of GaN and silicon laterally diffused metal oxide semiconductor (Si-LDMOS) products that deliver industry leading performance in a compact footprint to enable next-generation 5G cellular networks.

Spectrum expansion, higher order modulation, carrier aggregation, full dimension beam forming, and other enablers of 5G connectivity will require an expanded base of technologies to support enhanced mobile broadband connectivity. With spectrum usage and network footprints, multiple-input, multiple output (MIMO) technologies from four transmit (4TX) antennas to 64 TX and higher will be employed. The future of 5G networks will depend on GaN and Si-LDMOS technologies and NXP is at the forefront in its RF power amplifier development.

“Building on the success of 25 years of LDMOS leadership — NXP released the world’s first LDMOS product in 1992 — today, we are extending our RF leadership with industry leading GaN technology, developed with the highest linear efficiency for cellular applications,” said Paul Hart, senior vice president and general manager of NXP’s RF Power business. “Backed with the best supply chain, global applications support and unparalleled design expertise in the industry, NXP is positioned to be the leading RF partner for 5G solutions.”

At IMS 2018, NXP is introducing new RF GaN wideband power transistors and expanding its Airfast third-generation Si-LDMOS portfolio of macro and outdoor small cell solutions. The new offerings include:

  • A3G22H400-04S: Ideally suited for 40 W base stations, this GaN product yields up to 56.5 percent efficiency and 15.4 dB of gain and covers cellular bands from 1800 MHz to 2200 MHz.
  • A3G35H100-04S: Providing 43.8 percent efficiency and 14 dB of gain, this GaN product enables 16 TX MIMO solutions at 3.5 GHz.
  • A3T18H400W23S: This Si-LDMOS product is leading the way to 5G at 1.8 GHz with Doherty efficiency up to 53.4 percent and gain of 17.1 dB.
  • A3T21H456W23S: Covering the full 90 MHz band from 2.11 GHz to 2.2 GHz, this solution exemplifies NXP’s best-in-class Si-LDMOS performance for efficiency, RF power and signal bandwidth.
  • A3I20D040WN: Within NXP’s family of integrated ultra-wideband LDMOS products, this solution offers peak power of 46.5 dBm with 365 MHz wideband class AB performance of 32 dB of gain, 18 percent efficiency at 10 dB OBO.
  • A2I09VD030N: This offering boasts peak power of 46 dBm with class AB performance of 34.5 dB gain, 20 percent efficiency at 10 dB OBO. The RF bandwidth for this product is 575 MHz to 960 MHz.

The breadth of the company’s RF Power technologies—which include GaN, silicon-LDMOS, SiGe, and GaAs—allows product options for 5G that span frequency and power spectrums with varying levels of integration. This wide array of options, combined with the products that NXP builds for digital computing, and baseband processing, makes NXP a unique supplier of end-to-end 5G solutions.

To learn more, visit NXP at the International Microwave Symposium (IMS 2018) June 10-15 at booth #739 or at www.nxp.com/RF.

pSemi Corporation (formerly Peregrine Semiconductor), a Murata company focused on semiconductor integration, announces the expansion of its digital step attenuator (DSA) portfolio with a family of value, high-performance DSAs. The four value DSAs feature industry-leading attenuation accuracy at an entry-level price point.

“pSemi has a long, successful history of digital step attenuator development,” says Jim Cable, CTO at pSemi. “Our team introduced the world’s first single-chip DSA in 2004, and now, we are further expanding our DSA portfolio with the introduction of the value, high-performance DSAs. These four new DSAs nicely round out our DSA portfolio and complement our RF catalog parts.”

The value DSA family—the PE43620, PE43650, PE43665 and PE43670—are offered in a 2-bit, 5-bit, 6-bit or 7-bit configuration. These high-performance DSAs have excellent attenuation accuracy, low insertion loss and high linearity. The four products are available in compact QFN packages.

For 1K-quantity orders, the PE43620 DSA (2 bit, 50-ohm) is $0.63 each; the PE43650 (5 bit, 50-hm) is $1.44 each. The PE43665 (6-bit, 75-ohm) is $1.23 each, and the PE43670 (7-bit, 50-ohm) is $2.02each. Volume-production parts, samples and evaluation kits will be available in August.

pSemi Corporation is a Murata company driving semiconductor integration. pSemi builds on Peregrine Semiconductor’s 30-year legacy of technology advancements and strong IP portfolio but with a new mission: to enhance Murata’s capabilities with high-performance RF,

Quantum bits are now easier to manipulate for devices in quantum computing, thanks to enhanced spin-orbit interaction in silicon.

A silicon quantum computer chip has the potential to hold millions of quantum bits, or qubits, for much faster information processing than with the bits of today’s computers. This translates to high-speed database searches, better cybersecurity and highly efficient simulation of materials and chemical processes.

Now, research groups from Purdue University, the Technological University of Delft, Netherlands and the University of Wisconsin-Madison have discovered that silicon has unique spin-orbit interactions that can enable the manipulation of qubits using electric fields, without the need for any artificial agents.

Researchers are taking advantage of a newly found phenomenon in silicon that makes quantum bits easier to manipulate, leading to faster and longer-lived information processing via quantum computing. Credit: (Purdue University image/Rifat Ferdous)

“Qubits encoded in the spins of electrons are especially long-lived in silicon, but they are difficult to control by electric fields. Spin-orbit interaction is an important knob for the design of qubits that was thought to be small in this material, traditionally,” said Rajib Rahman, research assistant professor in Purdue’s School of Electrical and Computer Engineering.

The strength of spin-orbit interaction, which is the interaction of an electron’s spin with its motion, is an important factor for the quality of a qubit. The researchers found more prominent spin-orbit interaction than usual at the surface of silicon where qubits are located in the form of so-called quantum dots – electrons confined in three dimensions. Rahman’s lab identified that this spin-orbit interaction is anisotropic in nature – meaning that it is dependent on the angle of an external magnetic field – and strongly affected by atomic details of the surface.

“This anisotropy can be employed to either enhance or minimize the strength of the spin-orbit interaction,” said Rifat Ferdous, lead author of this work and a Purdue graduate research assistant in electrical and computer engineering. Spin-orbit interaction then affects qubits.

“If there is a strong spin-orbit interaction, the qubit’s lifetime is shorter but you can manipulate it more easily. The opposite happens with a weak spin-orbit interaction: The qubit’s lifetime is longer, but manipulation is more difficult,” Rahman said.

The researchers published their findings on June 5 in Nature Partner Journals – Quantum Information. The Wisconsin-Madison team fabricated the silicon device, the Delft team performed the experiments and the Purdue team led the theoretical investigation of the experimental observations. This work is supported by the Army Research Office, U.S. Department of Energy, the National Science Foundation and the European Research Council.

Upcoming work in Rahman’s lab will focus on taking advantage of the anisotropic nature of spin-orbit interactions to further enhance the coherence and control of qubits, and, therefore, the scaling up of quantum computer chips.

In the field of photovoltaic technologies, silicon-based solar cells make up 90% of the market. In terms of cost, stability and efficiency (20-22% for a typical solar cell on the market), they are well ahead of the competition.

However, after decades of research and investment, silicon-based solar cells are now close to their maximum theoretical efficiency. As a result, new concepts are required to achieve a long-term reduction in solar electricity prices and allow photovoltaic technology to become a more widely adopted way of generating power.

One solution is to place two different types of solar cells on top of each other to maximize the conversion of light rays into electrical power. These “double-junction” cells are being widely researched in the scientific community, but are expensive to make. Now research teams in Neuchâtel – from EPFL’s Photovoltaics Laboratory and the CSEM PV-center – have developed an economically competitive solution. They have integrated a perovskite cell directly on top of a standard silicon-based cell, obtaining a record efficiency of 25.2%. Their production method is promising, because it would add only a few extra steps to the current silicon-cell production process, and the cost would be reasonable. Their research has been published in Nature Materials.

This scanning electron microscopy image shows Silicon’s pyramids covered with perovskite. Credit: EPFL

Perovskite-on-silicon: a nanometric sandwich

Perovskite’s unique properties have prompted a great deal of research into its use in solar cells over the last few years. In the space of nine years, the efficiency of these cells has risen by a factor of six. Perovskite allows high conversion efficiency to be achieved at a potentially limited production cost.

In tandem cells, perovskite complements silicon: it converts blue and green light more efficiently, while silicon is better at converting red and infra-red light. “By combining the two materials, we can maximize the use of the solar spectrum and increase the amount of power generated. The calculations and work we have done show that a 30% efficiency should soon be possible,” say the study’s main authors Florent Sahli and Jérémie Werner.

However, creating an effective tandem structure by superposing the two materials is no easy task. “Silicon’s surface consists of a series of pyramids measuring around 5 microns, which trap light and prevent it from being reflected. However, the surface texture makes it hard to deposit a homogeneous film of perovskite,” explains Quentin Jeangros, who co-authored the paper.

When the perovskite is deposited in liquid form, as it usually is, it accumulates in the valleys between the pyramids while leaving the peaks uncovered, leading to short circuits.

A key layer ensuring an optimal microstructure

Scientists at EPFL and CSEM have gotten around that problem by using evaporation methods to form an inorganic base layer that fully covers the pyramids. That layer is porous, enabling it to retain the liquid organic solution that is then added using a thin-film deposition technique called spin-coating. The researchers subsequently heat the substrate to a relatively low temperature of 150°C to crystallize a homogeneous film of perovskite on top of the silicon pyramids.

“Until now, the standard approach for making a perovskite/silicon tandem cell was to level off the pyramids of the silicon cell, which decreased its optical properties and therefore its performance, before depositing the perovskite cell on top of it. It also added steps to the manufacturing process,” says Florent Sahli.

Updating existing technologies

The new type of tandem cell is highly efficient and directly compatible with monocrystalline silicon-based technologies, which benefit from long-standing industrial expertise and are already being produced profitably. “We are proposing to use equipment that is already in use, just adding a few specific stages. Manufacturers won’t be adopting a whole new solar technology, but simply updating the production lines they are already using for silicon-based cells,” explains Christophe Ballif, head of EPFL’s Photovoltaics Laboratory and CSEM’s PV-Center.

At the moment, research is continuing in order to increase efficiency further and give the perovskite film more long-term stability. Although the team has made a breakthrough, there is still work to be done before their technology can be adopted commercially.

Winbond Electronics Corporation, a global supplier of semiconductor memory solutions, today announced the introduction of the W25N01JW, a high-performance, 1.8V Serial NAND Flash memory IC delivering a new high in data-transfer rates: 83MB/s via a Quad Serial Peripheral Interface (QSPI).

Winbond’s new high-performance Serial NAND technology also supports a two-chip dual quad interface which gives a maximum data transfer rate of 166MB/s.

This high-speed Read operation, some four times faster than existing serial NAND memory devices offer, means that the 1.8V W25N01JW chip can replace SPI NOR Flash memory in automotive applications such as data storage for instrument clusters or the center information displays (CIDs).

This is important for automotive OEMs because the adoption of more sophisticated graphics displays in the instrument cluster, and larger display sizes of 7 inches and above in the CID, is increasing system memory requirements to capacities of 1Gbit and higher. At these capacities, serial NAND Flash has a markedly lower unit cost than that of SPI NOR Flash, and occupies a smaller board area per megabit of storage capacity.

SPI NOR Flash has been the preferred memory technology in automotive displays for many years because of its high read speed, which supports the fast boot requirements of automotive user interfaces, and because of its high reliability and long data retention. By raising the data transfer rate of its serial NAND technology to 83MB/s – matching the read speed of automotive SPI NOR Flash – Winbond has ensured that the W25N01JW can support fast boot operation and the demanding requirements of sophisticated graphics applications.

The W25N01JW also meets strict automotive requirements for quality and reliability. Built with high-reliability single-level sell (SLC) memory technology, and implementing 1-bit error correction code (ECC) on all Read and Write operations, it complies with the endurance, retention and quality requirements of the AEC-Q100 standard and relevant JEDEC specifications.

The W25N01JW device operates from -40°C to 105°C and retains data for 10 years at 85°C after 1,000 program/erase cycles, whereas eMMC can only retain data for a fraction of that time under these conditions even when used in SLC mode, which are today widely used for data storage in the CIDs of high-end vehicles.

“Cars’ large and attractive displays need higher memory capacity, beyond the ‘sweet spot’ of SPI NOR Flash, which is good for up to 512Mbits,” said William Chen, deputy director of the Flash Product Marketing Division at Winbond. “For systems that require high-speed memory in capacities of 1Gbit or higher, Winbond’s high-performance Serial NAND Flash is the new best choice for automotive OEMs, offering a combination of lower unit cost, smaller size and excellent reliability and data retention.”

The W25N01JW is available for sampling today in a capacity of 1Gbit. A two-chip implementation in dual-quad I/O mode provides 2Gbits of memory capacity and a maximum data transfer rate of 166MB/s.

The chip is available in industrial grade and in an extended-temperature automotive grade version operating at up to 105°C. It is compatible with standard SPI NAND Flash protocols. It is housed in standard 8mm x 6mm WSON and TFBGA packages that are footprint-compatible with standard SPI NOR Flash products.

Infrared spectroscopy is the benchmark method for detecting and analyzing organic compounds. But it requires complicated procedures and large, expensive instruments, making device miniaturization challenging and hindering its use for some industrial and medical applications and for data collection out in the field, such as for measuring pollutant concentrations. Furthermore, it is fundamentally limited by low sensitivities and therefore requires large sample amounts.

However, scientists at EPFL’s School of Engineering and at Australian National University (ANU) have developed a compact and sensitive nanophotonic system that can identify a molecule’s absorption characteristics without using conventional spectrometry.

The authors show a pixelated sensor metasurface for molecular spectroscopy. It consists of metapixels designed to concentrate light into nanometer-sized volumes in order to amplify and detect the absorption fingerprint of analyte molecules at specific resonance wavelengths. Simultaneous imaging-based read-out of all metapixels provides a spatial map of the molecular absorption fingerprint sampled at the individual resonance wavelengths. This pixelated absorption map can be seen as a two-dimensional barcode of the molecular fingerprint, which encodes the characteristic absorption bands as distinct features of the resulting image. Credit: EPFL

Their system consists of an engineered surface covered with hundreds of tiny sensors called metapixels, which can generate a distinct bar code for every molecule that the surface comes into contact with. These bar codes can be massively analyzed and classified using advanced pattern recognition and sorting technology such as artificial neural networks. This research – which sits at the crossroads of physics, nanotechnology and big data – has been published in Science.

Translating molecules into bar codes

The chemical bonds in organic molecules each have a specific orientation and vibrational mode. That means every molecule has a set of characteristic energy levels, which are commonly located in the mid-infrared range – corresponding to wavelengths of around 4 to 10 microns. Therefore, each type of molecule absorbs light at different frequencies, giving each one a unique “signature.” Infrared spectroscopy detects whether a given molecule is present in a sample by seeing if the sample absorbs light rays at the molecule’s signature frequencies. However, such analyses require lab instruments with a hefty size and price tag.

The pioneering system developed by the EPFL scientists is both highly sensitive and capable of being miniaturized; it uses nanostructures that can trap light on the nanoscale and thereby provide very high detection levels for samples on the surface. “The molecules we want to detect are nanometric in scale, so bridging this size gap is an essential step,” says Hatice Altug, head of EPFL’s BioNanoPhotonic Systems Laboratory and a coauthor of the study.

The system’s nanostructures are grouped into what are called metapixels so that each one resonates at a different frequency. When a molecule comes into contact with the surface, the way the molecule absorbs light changes the behavior of all the metapixels it touches.

“Importantly, the metapixels are arranged in such a way that different vibrational frequencies are mapped to different areas on the surface,” says Andreas Tittl, lead author of the study.

This creates a pixelated map of light absorption that can be translated into a molecular bar code – all without using a spectrometer.

The scientists have already used their system to detect polymers, pesticides and organic compounds. What’s more, their system is compatible with CMOS technology.

“Thanks to our sensors’ unique optical properties, we can generate bar codes even with broadband light sources and detectors,” says Aleksandrs Leitis, a coauthor of the study.

There are a number of potential applications for this new system. “For instance, it could be used to make portable medical testing devices that generate bar codes for each of the biomarkers found in a blood sample,” says Dragomir Neshev, another coauthor of the study.

Artificial intelligence could be used in conjunction with this new technology to create and process a whole library of molecular bar codes for compounds ranging from protein and DNA to pesticides and polymers. That would give researchers a new tool for quickly and accurately spotting miniscule amounts of compounds present in complex samples.

WIN Semiconductors Corp (TPEx:3105), the world’’s largest pure-play compound semiconductor foundry, has expanded its gallium nitride (GaN) process capabilities to include a 0.45?m-gate technology that supports current and future 5G applications. The NP45-11 GaN-on-SiC process allows customers to design hybrid Doherty power amplifiers used in 5G applications including massive MIMO (multiple-input and multiple-output) wireless antenna systems. Similar to macro-cell applications, MIMO base stations often combine Doherty power amplifiers with linearization techniques to meet demanding linearity and efficiency specifications of today’s wireless infrastructure.

GaN devices outperform the incumbent LDMOS technology, offering superior efficiency, instantaneous bandwidth and linearity, particularly in the higher frequency bands utilized in 5G radio access networks.

Ideal for use in sub-6 GHz 5G applications including macro-cell transmitters and MIMO access points, the NP45-11 technology supports power applications from 100 MHz through 6GHz. This discrete transistor process is environmentally rugged, incorporating advanced moisture protection and meets the JEDEC JESD22-A110 biased HAST qualification at 55 volts. Combined with WIN Semiconductors’ environmentally rugged high voltage passive technology, IP3M-01, the NP45-11 technology enables hybrid power amplifiers in a low cost plastic package.

The NP45-11 technology is fabricated on 100mm silicon carbide substrates and operates at a drain bias of 50 volts. In the 2.7GHz band, this technology provides saturated output power of 7 watts/mm with 18 dB linear gain and more than 65% power added efficiency without harmonic tuning.

“5G radio access networks create several challenges to power amplifier designs used in MIMO systems. High output power and linear efficiency are primary design objectives to meet performance specifications and lower total cost of ownership. The tradeoff between output power and linearized efficiency is significant because of the high peak-to-average power ratio employed in today’s wireless modulation schemes. This tradeoff becomes more difficult in 5G applications due to greater instantaneous bandwidth requirements and higher operating frequency,” said David Danzilio, Senior Vice President of WIN Semiconductors Corp.

Imec today announced at the International Microwave Symposium (IMS, Philadelphia, USA), the world’s first CMOS 140GHz radar-on-chip system with integrated antennas in standard 28nm technology. The achievement is an important step in the development of radar-based sensors for a myriad of smart intuitive applications, such as building security, remote health monitoring of car drivers, breathing and heart rate of patients, and gesture recognition for man-machine interaction.

Radars are extremely promising as sensors for contactless, non-intrusive interaction in internet-of-things applications such as people detection & classification, vital signs monitoring and gesture interfacing. A wide adoption will only be possible if radars achieve a higher resolution, become much smaller, more power-efficient to run, and cheaper to produce and to buy. This is what imec’s research on 140GHz radar technology targets.

This low-power 140GHz radar solution comprises an imec proprietary two antenna SISO (Single Input Single Output) radar transceiver chip and a frequency modulated continuous wave phase-locked loop (FMCW PLL), off-the shelf ADCs and FPGA and a Matlab chain. The transceiver features on-chip antennas achieving a gain close to 3dBi. The excellent radar link budgets are supported thanks to the transmitter Effective Isotropic Radiated Power (EIRP)  that exceeds 9dBm and a receiver noise figure below 6.4dB. The total power consumption for transmitter and receiver remains below 500mW, which can be further reduced by duty cycling. The FMCW PLL  enables  fast slopes up to 500MHz/ms over a 10GHz bandwidth around 140GHz with a slope linearity error below 0.5% and has a power consumption below 50mW. The FPGA contains real-time implementation of basic radar processing functions such as FFTs (Fast Fourier Transforms) and filters, and is complemented by a Matlab chain for detections, CFAR (Constant False Alarm Rate), direction-of-arrival estimation and other advanced radar processing.

“With our prototype radar, we have demonstrated all critical specs for radar technology in 28nm standard CMOS technology,” said Wim Van Thillo, IoT program director at imec. “We are well advanced in incorporating multiple antenna paths in our most recent generation solution, which will enable a fine angular resolution of 1.5cm in a complete MIMO radar form factor of only a few square centimeters. We expect this prototype in the lab by the end of 2018, at which point our partners can start building their application demonstrators. First applications are expected to be person detection and classification for smart buildings, remote car driver vital signs monitoring (as cars evolve towards self-driving vehicles), and gesture recognition for intuitive man-machine interactions. Plenty more innovations will be enabled by this technology, once app developers start working with it.”

This imec 140GHz radar open innovation R&D collaborative program has been endorsed by Panasonic, and imec invites potential interested parties to join.

Ever shrinking transistors are the key to faster and more efficient computer processing. Since the 1970s, advancements in electronics have largely been driven by the steady pace with which these tiny components have grown simultaneously smaller and more powerful–right down to their current dimensions on the nanometer scale. But recent years have seen this progress plateau, as researchers grapple with whether transistors may have finally hit their size limit. High among the list of hurdles standing in the way of further miniaturization: problems caused by “leakage current.”

Leakage current results when the gap between two metal electrodes narrows to the point that electrons are no longer contained by their barriers, a phenomenon known as quantum mechanical tunnelling. As the gap continues to decrease, this tunnelling conduction increases at an exponentially higher rate, rendering further miniaturization extremely challenging. Scientific consensus has long held that vacuum barriers represent the most effective means to curtail tunnelling, making them the best overall option for insulating transistors. However, even vacuum barriers can allow for some leakage due to quantum tunnelling.

In a highly interdisciplinary collaboration, researchers across Columbia Engineering, Columbia University Department of Chemistry, Shanghai Normal University, and the University of Copenhagen have upended conventional wisdom, synthesizing the first molecule capable of insulating at the nanometer scale more effectively than a vacuum barrier. Their findings are published online today in Nature.

“We’ve reached the point where it’s critical for researchers to develop creative solutions for redesigning insulators. Our molecular strategy represents a new design principle for classic devices, with the potential to support continued miniaturization in the near term,” said Columbia Engineering physicist and co-author Latha Venkataraman, who heads the lab where researcher Haixing Li conducted the project’s experimental work. Molecular synthesis was carried out in the Colin Nuckolls Lab at Columbia’s Department of Chemistry, in partnership with Shengxiong Xiao at Shanghai Normal University.

The team’s insight was to exploit the wave nature of electrons. By designing an extremely rigid silicon-based molecule under 1 nm in length that exhibited comprehensive destructive interference signatures, they devised a novel technique for blocking tunnelling conduction at the nanoscale.

“This quantum interference-based approach sets a new standard for short insulating molecules,” said lead author Marc Garner, a chemist in the University of Copenhagen’s Solomon Lab, which handled the theoretical work. “Theoretically, interference can lead to complete cancellation of tunneling probability, and we’ve shown that the insulating component in our molecule is less conducting than a vacuum gap of same dimensions. At the same time, our work also improves on recent research into carbon-based systems, which were thought to be the best molecular insulators until now.”

Destructive quantum interference occurs when the peaks and valleys of two waves are placed exactly out of phase, annulling oscillation. Electronic waves can be thought of as analogous to sound waves–flowing through barriers just as sound waves “leak” through walls. The unique properties exhibited by the team’s synthetic molecule mitigated tunneling without requiring, in this analogy, a thicker wall.

Their silicon-based strategy also presents a potentially more factory-ready solution. While recent research into carbon nanotubes holds promise for industrial applications over the next decade or so, this insulator–compatible with current industry standards–could be more readily implemented.

“Congratulations to the team on this breakthrough,” said Mark Ratner, a pioneer in the field of molecular electronics and professor emeritus at Northwestern University who was not involved in the study. “Using interference to create an insulator has been ignored up to this date. This paper demonstrates the ability of interference, in a silicon-based sigma system, which is quite impressive.”

This breakthrough grew out of the team’s larger project on silicon-based molecule electronics, begun in 2010. The group arrived at their latest discovery by bucking the trend. Most research in this field aims to create highly conducting molecules, as low conductance is rarely considered a desirable property in electronics. Yet insulating components may actually prove to be of greater value to future optimization of transistors, due to the inherent energy inefficiencies caused by leakage currents in smaller devices.

As a result, their work has yielded new understanding of the fundamental underlying mechanisms of conduction and insulation in molecular scale devices. The researchers will build on this insight by next clarifying the details of structure-function relationships in silicon-based molecular components.

“This work has been extremely gratifying for us, because in the course of it we have repeatedly discovered new phenomena,” said Venkataraman. “We have previously shown that silicon molecular wires can function as switches, and now we’ve demonstrated that by altering their structure, we can create insulators. There is a lot to be learned in this area that will help shape the future of nanoscale electronics.”

Researchers at Oregon State University are looking at a highly durable organic pigment, used by humans in artwork for hundreds of years, as a promising possibility as a semiconductor material.

Findings suggest it could become a sustainable, low-cost, easily fabricated alternative to silicon in electronic or optoelectronic applications where the high-performance capabilities of silicon aren’t required.

Optoelectronics is technology working with the combined use of light and electronics, such as solar cells, and the pigment being studied is xylindein.

“Xylindein is pretty, but can it also be useful? How much can we squeeze out of it?” said Oregon State University physicist Oksana Ostroverkhova. “It functions as an electronic material but not a great one, but there’s optimism we can make it better.”

Xylindien is secreted by two wood-eating fungi in the Chlorociboria genus. Any wood that’s infected by the fungi is stained a blue-green color, and artisans have prized xylindein-affected wood for centuries.

The pigment is so stable that decorative products made half a millennium ago still exhibit its distinctive hue. It holds up against prolonged exposure to heat, ultraviolet light and electrical stress.

“If we can learn the secret for why those fungi-produced pigments are so stable, we could solve a problem that exists with organic electronics,” Ostroverkhova said. “Also, many organic electronic materials are too expensive to produce, so we’re looking to do something inexpensively in an ecologically friendly way that’s good for the economy.”

With current fabrication techniques, xylindein tends to form non-uniform films with a porous, irregular, “rocky” structure.

“There’s a lot of performance variation,” she said. “You can tinker with it in the lab, but you can’t really make a technologically relevant device out of it on a large scale. But we found a way to make it more easily processed and to get a decent film quality.”

Ostroverkhova and collaborators in OSU’s colleges of Science and Forestry blended xylindein with a transparent, non-conductive polymer, poly(methyl methacrylate), abbreviated to PMMA and sometimes known as acrylic glass. They drop-cast solutions both of pristine xylindein and a xlyindein-PMMA blend onto electrodes on a glass substrate for testing.

They found the non-conducting polymer greatly improved the film structure without a detrimental effect on xylindein’s electrical properties. And the blended films actually showed better photosensitivity.

“Exactly why that happened, and its potential value in solar cells, is something we’ll be investigating in future research,” Ostroverkhova said. “We’ll also look into replacing the polymer with a natural product – something sustainable made from cellulose. We could grow the pigment from the cellulose and be able to make a device that’s all ready to go.

“Xylindein will never beat silicon, but for many applications, it doesn’t need to beat silicon,” she said. “It could work well for depositing onto large, flexible substrates, like for making wearable electronics.”

This research, whose findings were recently published in MRS Advances, represents the first use of a fungus-produced material in a thin-film electrical device.

“And there are a lot more of the materials,” Ostroverkhova said. “This is just first one we’ve explored. It could be the beginning of a whole new class of organic electronic materials.”