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D2S, a supplier of GPU-accelerated solutions for semiconductor manufacturing, today announced the unveiling of the fifth generation of its computational design platform (CDP), which enables extremely fast and precise simulations for semiconductor design and manufacturing. Featuring NVIDIA Pascal-based Tesla P40 GPUs, the fifth-generation CDP achieves 888 Teraflops of processing speed–more than twice as fast as the previous-generation CDP from D2S. The first two units of the fifth-generation CDP will be delivered by the end of the second calendar quarter of 2017, bringing the total number of CDPs across all five platform generations installed worldwide to 20–representing more than five Peta-FLOPs of computing power. CDPs are architected to ensure the high speed, precision and reliability required for 24×7 cleanroom production environments.

“Seismic changes are underway in the photomask and semiconductor industry, prompting the need for greater simulation capability,” stated Aki Fujimura, CEO of D2S. “Inverse lithography technology (ILT) and complex mask shapes, which are already being utilized in some leading-edge chip designs, will be increasingly needed as the industry migrates to smaller design nodes. Significant progress is being made with multi-beam mask writing, which provides write times that are independent of shape count or complexity–making it ideal for these complex features. Progress also continues on EUV mask development, which will require extreme mask writing precision as well as high shape counts. However, with all of these major technology transitions, the computational power required to precisely simulate the physical effects of photomask designs and semiconductor processes will skyrocket–driving the need for GPU acceleration to enable simulation-based processing in reasonable run times.”

The D2S CDP is an extremely powerful processing solution that can simulate the entire mask plane (1.4 quintillion pixels). It is engineered for high reliability, redundancy and recovery to support stringent environmental requirements, and fully conforms with SEMI S2. The water-cooled CDP design is optimized for cleanroom manufacturing environments.

The newest application for the D2S CDP is inline linearity correction for multi-beam mask writing, which provides pixel-level dose correction to enhance the printability of masks incorporating more complex and smaller features. A summary of the current semiconductor manufacturing applications where D2S GPU-accelerated CDPs are being used include:

  • model-based mask data preparation (MB-MDP) for designing leading-edge photomasks that require increasingly complex mask shapes;
  • wafer plane analysis of mask images captured in scanning electron microscopy (SEM) systems to accurately identify mask problems that matter to the wafer in interactive time;
  • inline thermal-effect correction of eBeam mask writers to lower write times to an acceptable level;
    geometric checking and manipulation of curvilinear shapes on masks and wafers; and
  • inline linearity correction and printability enhancement for the NuFlare MBM-1000 multi-beam mask writer

“Multi-beam is an enabling technology for writing curvilinear ILT features due to its ability to handle any mask shape without loss of accuracy or speed,” stated Noriaki Nakayamada, chief specialist at NuFlare Technology. “Since curvilinear mask data correction for dose and resist effects is required to make ILT possible, implementing inline linearity correction in multi-beam machines is useful, as it eliminates the need to add an extra offline data preparation step. However, doing so is extremely compute-intensive and difficult to accomplish. D2S GPU acceleration technology makes inline linearity correction possible for the first time, which can significantly reduce turnaround time for mask processing.”

“GPUs excel at simulating natural phenomena and work well in low latency situations, making them an ideal solution for advanced semiconductor manufacturing,” added Fujimura. “We’re pleased to see that the industry is increasingly recognizing the benefits of GPU acceleration. For example, the Photomask Japan Symposium taking place this week in Yokohama is, for the first time, dedicating multiple sessions of its program to the use of GPUs in mask making. That’s an important signal that GPU acceleration has arrived and will be a key enabler for leading-edge mask and chip designs.”

D2S offers its GPU-accelerated platform as part of its TrueMask family of products and as custom OEM additions to manufacturing systems. D2S will present a paper co-authored with NuFlare Technology on GPU-accelerated inline linearity correction during the “Use of GPU in Mask Making II” session at the Photomask Japan 2017 Symposium on Wednesday, April 5 from 16:30 to 18:00.

A recent study, affiliated with UNIST has created a three-dimensional, tactile sensor that could detect wide pressure ranges from human body weight to a finger touch. This new sensor with transparent features is capable of generating an electrical signal based on the sensed touch actions, also, consumes far less electricity than conventional pressure sensors.

The breakthrough comes from a research, conducted by Professor Jang-Ung Park of Materials Science and Engineering and his research team at UNIST. In the study, the research team presented a novel method of fabricating a transistor-type active-matrix pressure sensor using foldable substrates and air-dielectric layers.

This image shows the transistor-type active-matrix 3-D pressure sensors with air-dielectric layers. Credit: UNIST

This image shows the transistor-type active-matrix 3-D pressure sensors with air-dielectric layers. Credit: UNIST

Today, most transistors are created with silicon channel and silicon oxide-based dielectrics. However, these transistors have been found to be either lacking transparency or inflexible, which may hinder their utility in fabricating highly-integrated pressure sensor arrays and transparent pressure sensors.

In this regard, Professor Park’s team decided to use highly-conductive and transparent graphene transistors with air-dielectric layers. The sensor can detect different types of touch-including swiping and tapping..

“Using air as the dielectric layer in graphene field-effect transistors (FETs) can significantly improve transistor performance due to the clean interface between graphene channel and air,” says Professor Park. “The thickness of the air-dielectric layers is determined by the applied pressure. With that technology, it would be possible to detect pressure changes far more effectively.”

A convantional touch panel, which may be included in a display device, reacts to the static electrical when pressure is applied to the monitor screen. With this method, the position on screen contacted by a finger, stylus, or other object can be easily detected using changes in pressure, but can not provide the intensity of pressure.

The research team placed graphene channel, metal nanowire electrodes, as well as an elastic body capable of trapping air on one side of the foldable substrate. Then they covered the other side of the substrate, like a lid and kept the air. In this transistor, the force pressing the elastic body is transferred to the air-dielectric layer and alters its thickness. Such changes in the thickness of the air-dielectric layer is converted into an electrical signal and transmitted via metal nanowires and the graphene channel, expressing both the position and the intensity of the pressure.

This is regarded as a promising technology as it enables the successful implementation of active-matrix pressure sensors. Moreover, when compared with the passive-matrix type, it consumes less power and has a faster response time.

It is possible to send and receive signals only by flowing electricity to the place where pressure is generated. The change in the thickness of the air dielectric layer is converted into an electrical signal to represent the position and intensity of the pressure. In addition, since all the substrates, channels, and electrode materials used in this process are all transparent, they can also be manufactured with invisible pressure sensors.

“This sensor is capable of simultaneously measuring anything from lower pressure (less than 10 kPa), such as gentle tapping to high pressure (above 2 MPa), such as human body weight,” says Sangyoon Ji (Combined M.S./Ph.D. student of Materials Science and Engineering), the first co-author of the study. “It can be also applied to 3D touchscreen panels or smart running shoes that can analyze life patterns of people by measuring their weight distribution.”

“This study not only solves the limitations of conventional pressure sensors, but also suggests the possibility to apply them to various fields by combining pressure sensor with other electronic devices such as display.” says Professor Park.

Carbon nanotubes can be used to make very small electronic devices, but they are difficult to handle. University of Groningen scientists, together with colleagues from the University of Wuppertal and IBM Zurich, have developed a method to select semiconducting nanotubes from a solution and make them self-assemble on a circuit of gold electrodes. The results were published in the journal Advanced Materials on 5 April.

The results look deceptively simple: a self-assembled transistor with nearly 100 percent purity and very high electron mobility. But it took ten years to get there. University of Groningen Professor of Photophysics and Optoelectronics Maria Antonietta Loi designed polymers which wrap themselves around specific carbon nanotubes in a solution of mixed tubes. Thiol side chains on the polymer bind the tubes to the gold electrodes, creating the resultant transistor.

This is an artist's impression of carbon nanotubes wrapped in polymers with thiol side chains (yellow spheres) and assembled on gold electrodes. Credit: Arjen Kamp

This is an artist’s impression of carbon nanotubes wrapped in polymers with thiol side chains (yellow spheres) and assembled on gold electrodes. Credit: Arjen Kamp

Patent

‘In our previous work, we learned a lot about how polymers attach to specific carbon nanotubes’, Loi explains. These nanotubes can be depicted as a rolled sheet of graphene, the two-dimensional form of carbon. ‘Depending on the way the sheets are rolled up, they have properties ranging from semiconductor to semi-metallic to metallic.’ Only the semiconductor tubes can be used to fabricate transistors, but the production process always results in a mixture.

‘We had the idea of using polymers with thiol side chains some time ago’, says Loi. The idea was that as sulphur binds to metals, it will direct polymer-wrapped nanotubes towards gold electrodes. While Loi was working on the problem, IBM even patented the concept. ‘But there was a big problem in the IBM work: the polymers with thiols also attached to metallic nanotubes and included them in the transistors, which ruined them.’

Solution

Loi’s solution was to reduce the thiol content of the polymers, with the assistance of polymer chemists from the University of Wuppertal. ‘What we have now shown is that this concept of bottom-up assembly works: by using polymers with a low concentration of thiols, we can selectively bring semiconducting nanotubes from a solution onto a circuit.’ The sulphur-gold bond is strong, so the nanotubes are firmly fixed: enough even to stay there after sonication of the transistor in organic solvents.

The production process is simple: metallic patterns are deposited on a carrier , which is then dipped into a solution of carbon nanotubes. The electrodes are spaced to achieve proper alignment: ‘The tubes are some 500 nanometres long, and we placed the electrodes for the transistors at intervals of 300 nanometres. The next transistor is over 500 nanometres away.’ The spacing limits the density of the transistors, but Loi is confident that this could be increased with clever engineering.

‘Over the last years, we have created a library of polymers that select semiconducting nanotubes and developed a better understanding of how the structure and composition of the polymers influences which carbon nanotubes they select’, says Loi. The result is a cheap and scalable production method for nanotube electronics. So what is the future for this technology? Loi: ‘It is difficult to predict whether the industry will develop this idea, but we are working on improvements, and this will eventually bring the idea closer to the market.’

USB flash drives are already common accessories in offices and college campuses. But thanks to the rise in printable electronics, digital storage devices like these may soon be everywhere — including on our groceries, pill bottles and even clothing.

Duke University researchers have brought us closer to a future of low-cost, flexible electronics by creating a new “spray-on” digital memory device using only an aerosol jet printer and nanoparticle inks.

Duke University researchers have developed a new 'spray-on' digital memory (upper left) that could be used to build programmable electronic devices on flexible materials like paper, plastic or fabric. To demonstrate a simple application of their device, they used their memory to program different patterns of four LED lights in a simple circuit. Credit: Matthew Catenacci

Duke University researchers have developed a new ‘spray-on’ digital memory (upper left) that could be used to build programmable electronic devices on flexible materials like paper, plastic or fabric. To demonstrate a simple application of their device, they used their memory to program different patterns of four LED lights in a simple circuit. Credit: Matthew Catenacci

The device, which is analogous to a 4-bit flash drive, is the first fully-printed digital memory that would be suitable for practical use in simple electronics such as environmental sensors or RFID tags. And because it is jet-printed at relatively low temperatures, it could be used to build programmable electronic devices on bendable materials like paper, plastic or fabric.

“We have all of the parameters that would allow this to be used for a practical application, and we’ve even done our own little demonstration using LEDs,” said Duke graduate student Matthew Catenacci, who describes the device in a paper published online March 27 in the Journal of Electronic Materials.

At the core of the new device, which is about the size of a postage stamp, is a new copper-nanowire-based printable material that is capable of storing digital information.

“Memory is kind of an abstract thing, but essentially it is a series of ones and zeros which you can use to encode information,” said Benjamin Wiley, an associate professor of chemistry at Duke and an author on the paper.

Most flash drives encode information in series of silicon transistors, which can exist in a charged state, corresponding to a “one,” and an uncharged state, corresponding to a “zero,” Wiley said.

The new material, made of silica-coated copper nanowires encased in a polymer matrix, encodes information not in states of charge but instead in states of resistance. By applying a small voltage, it can be switched between a state of high resistance, which stops electric current, and a state of low resistance, which allows current to flow.

And, unlike silicon, the nanowires and the polymer can be dissolved in methanol, creating a liquid that can be sprayed through the nozzle of a printer.

“We have developed a way to make the entire device printable from solution, which is what you would want if you wanted to apply it to fabrics, RFID tags, curved and flexible substrates, or substrates that can’t sustain high heat,” Wiley said.

To create the device, Catenacci first used commercially-available gold nanoparticle ink to print a series of gold electrodes onto a glass slide. He then printed the copper-nanowire memory material over the gold electrodes, and finally printed a second series of electrodes, this time in copper.

To demonstrate a simple application, Catenacci connected the device to a circuit containing four LED lights. “Since we have four bits, we could program sixteen different states,” Catenacci said, where each “state” corresponds to a specific pattern of lights. In a real-world application, each of these states could be programmed to correspond to a number, letter, or other display symbol.

Though other research groups have fabricated similar printable memory devices in recent years, this is the first to combine key properties that are necessary for practical use. The write speed, or time it takes to switch back and forth between states, is around three microseconds, rivaling the speed of flash drives. Their tests indicate that written information may be retained for up to ten years, and the material can be re-written many times without degrading.

While these devices won’t be storing digital photos or music any time soon — their memory capacity is much too small for that — they may be useful in applications where low cost and flexibility are key, the researchers say.

“For example, right now RFID tags just encode a particular produce number, and they are typically used for recording inventory,” Wiley said. “But increasingly people also want to record what environment that product felt — such as, was this medicine always kept at the right temperature? One way these could be used would be to make a smarter RFID tags that could sense their environments and record the state over time.”

It would be difficult to overestimate the importance of silicon when it comes to computing, solar energy, and other technological applications. (Not to mention the fact that it makes up an awful lot of the Earth’s crust.) Yet there is still so much to learn about how to harness the capabilities of element number fourteen.

The most-common form of silicon crystallizes in the same structure as diamond. But other forms can be created using different processing techniques. New work led by Carnegie’s Tim Strobel and published in Physical Review Letters shows that one form of silicon, called Si-III (or sometimes BC8), which is synthesized using a high-pressure process, is what’s called a narrow band gap semiconductor.

What does this mean and why does it matter?

Metals are compounds that are capable of conducting the flow of electrons that makes up an electric current, and insulators are compounds that conduct no current at all. Semiconductors, which are used extensively in electronic circuitry, can have their electrical conductivity turned on and off–an obviously useful capability. This ability to switch conductivity is possible because some of their electrons can move from lower-energy insulating states to higher-energy conducting states when subjected to an input of energy. The energy required to initiate this leap is called a band gap.

The diamond-like form of silicon is a semiconductor and other known forms are metals, but the true properties of Si-III remained unknown until now. Previous experimental and theoretical research suggested that Si-III was a poorly conducting metal without a band gap, but no research team had been able to produce a pure and large enough sample to be sure.

By synthesizing pure, bulk samples of Si-III, Strobel and his team were able to determine that Si-III is actually a semiconductor with an extremely narrow band gap, narrower than the band gap of diamond-like silicon crystals, which is the most-commonly utilized kind. This means that Si-III could have uses beyond the already full slate of applications for which silicon is currently used. With the availability of pure samples, the team was able to fully characterize the electronic, optical, and thermal transport properties of Si-III for the first time.

“Historically, the correct recognition of germanium as a semiconductor instead of the metal it was once widely believed to be truly helped to start the modern semiconductor era; similarly, the discovery of semiconducting properties of Si-III might lead to unpredictable technological advancement,” remarked lead author, Carnegie’s Haidong Zhang. “For example, the optical properties of Si-III in the infrared region are particularly interesting for future plasmonic applications.”

Tiny “black holes” on a silicon wafer make for a new type of photodetector that could move more data at lower cost around the world or across a datacenter. The technology, developed by electrical engineers at the University of California, Davis, and W&WSens Devices, Inc. of Los Altos, Calif., a Silicon Valley startup, is described in a paper published April 3 in the journal Nature Photonics.

“We’re trying to take advantage of silicon for something silicon cannot usually do,” said Saif Islam, professor of electrical and computer engineering at UC Davis, who co-lead the project together with the collaborators at W&WSens Devices, Inc. Existing high-speed photodetector devices use materials such as gallium arsenide. “If we don’t need to add non-silicon components and can monolithically integrate with electronics into a single silicon chip, the receivers become much cheaper.”

The new detector uses tapered holes in a silicon wafer to divert photons sideways, preserving the speed of thin-layer silicon and the efficiency of a thicker layer. So far, Islam’s group has built an experimental photodetector and solar cell using the new technology. The photodetector can convert data from optical to electronics at 20 gigabytes per second (or 25 billion bits per second, more than 200 times faster than your cable modem) with a quantum efficiency of 50 percent, the fastest yet reported for a device of this efficiency.

Datacenters need fast connections

The growth of datacenters that power the internet “cloud” has created a demand for devices to move large amounts of data, very fast, over short distances of a few yards to hundreds of yards. Such connections could also be used for high-speed home connections, Islam said.

When computer engineers want to move large amounts of data very fast, whether across the world or across a data center, they use fiber-optic cables that transmit data as pulses of light. But these signals need to be converted to electronic pulses at the receiving end by a photodetector. You can use silicon as a photodetector – incoming photons generate a flow of electrons. But there’s a tradeoff between speed and efficiency. To capture most of the photons, the piece of silicon needs to be thick, and that makes it relatively slow. Make the silicon thinner so it works faster, and too many photons get lost.

Instead, circuit designers have used materials such as gallium arsenide and indium phosphide to make high-speed, high-efficiency photodetectors. Gallium arsenide, for example, is about ten times as efficient as a silicon at the same scale and wavelength. But it is significantly more expensive and cannot be monolithically integrated with silicon electronics.

Tapered holes as light traps

Islam’s group began by experimenting with ways to increase the efficiency of silicon by adding tiny pillars or columns, then holes to the silicon wafer. After two years of experiments, they settled on a pattern of holes that taper towards the bottom.

“We came up with a technology that bends the incoming light laterally through thin silicon,” Islam said.

The idea is that photons enter the holes and get pulled sideways into the silicon. The wafer itself is about two microns thick, but because they move sideways, the photons travel through 30 to 40 microns of silicon, like the ripple of waves on a pond when a pebble is dropped into the water.

The holes-based device can also potentially work with a wider range of wavelengths of light than current technology, Islam said.

Cree, Inc. (Nasdaq: CREE) announces the new XLamp XP-G3 Royal Blue LED, the industry’s highest performing Royal Blue LED. The new XP-G3 LED doubles the maximum light output of similar size competing LEDs and delivers breakthrough wall-plug efficiency of up to 81 percent. This superior performing Royal Blue LED expands Cree’s leading high power portfolio, enabling lighting manufacturers to deliver differentiated LED solutions for applications such as horticulture, architectural and entertainment lighting.

royal blue led

Using the new XP-G3 Royal Blue LED and the recently introduced XP-E High Efficiency Photo Red LED, Cree has created a new horticulture reference design that achieves a Photosynthetic Photon Flux (PPF) efficiency of up to 3.2 μmol/J at steady-state, which is over 50 percent more efficient than the traditional high pressure sodium solutions in use today. The XP-G3 Royal Blue LED delivers up to 3402 mW radiant flux, which corresponds to 13 μmol/s PPF, at its 2A maximum current and 85 C junction temperature.

“Our newest horticulture-optimized products help lighting manufacturers push LED horticulture systems into mainstream use,” said Dave Emerson, Cree LEDs senior vice president and general manager. “Cree’s high power LED technology provides the best combination of photon output, efficiency and reliability to drive the replacement of outdated high pressure sodium lights with LED lighting solutions that minimize power consumption and maximize crop yield.”

The XP-G3 Royal Blue LED is built on Cree’s ceramic high-power technology, which can deliver excellent lifetimes even at the extreme temperature of 105 C. Additionally, horticulture lighting manufacturers can immediately take advantage of the existing ecosystem of drivers and optics proven to work with Cree’s other 3.45 mm footprint XP products to shorten their time to market.

An innovative new technique to produce the quickest, smallest, highest-capacity memories for flexible and transparent applications could pave the way for a future golden age of electronics.

Engineering experts from the University of Exeter have developed innovative new memory using a hybrid of graphene oxide and titanium oxide. Their devices are low cost and eco-friendly to produce, are also perfectly suited for use in flexible electronic devices such as ‘bendable’ mobile phone, computer and television screens, and even ‘intelligent’ clothing.

Crucially, these devices may also have the potential to offer a cheaper and more adaptable alternative to ‘flash memory’, which is currently used in many common devices such as memory cards, graphics cards and USB computer drives.

The research team insist that these innovative new devices have the potential to revolutionise not only how data is stored, but also take flexible electronics to a new age in terms of speed, efficiency and power.

The research is published in the leading scientific journal ACS Nano.

Professor David Wright, an Electronic Engineering expert from the University of Exeter and lead author of the paper said: “Using graphene oxide to produce memory devices has been reported before, but they were typically very large, slow, and aimed at the ‘cheap and cheerful’ end of the electronics goods market.

“Our hybrid graphene oxide-titanium oxide memory is, in contrast, just 50 nanometres long and 8 nanometres thick and can be written to and read from in less than five nanoseconds — with one nanometre being one billionth of a metre and one nanosecond a billionth of a second.”

Professor Craciun, a co-author of the work, added: “Being able to improve data storage is the backbone of tomorrow’s knowledge economy, as well as industry on a global scale. Our work offers the opportunity to completely transform graphene-oxide memory technology, and the potential and possibilities it offers.”

A new way to grow narrow ribbons of graphene, a lightweight and strong structure of single-atom-thick carbon atoms linked into hexagons, may address a shortcoming that has prevented the material from achieving its full potential in electronic applications. Graphene nanoribbons, mere billionths of a meter wide, exhibit different electronic properties than two-dimensional sheets of the material.

This graphene nanoribbon was made bottom-up from a molecular precursor. Nanoribbon width and edge effects influence electronic behavior. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy; scanning tunneling microscopy by Chuanxu Ma and An-Ping Li

This graphene nanoribbon was made bottom-up from a molecular precursor. Nanoribbon width and edge effects influence electronic behavior. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy; scanning tunneling microscopy by Chuanxu Ma and An-Ping Li

“Confinement changes graphene’s behavior,” said An-Ping Li, a physicist at the Department of Energy’s Oak Ridge National Laboratory. Graphene in sheets is an excellent electrical conductor, but narrowing graphene can turn the material into a semiconductor if the ribbons are made with a specific edge shape.

Previous efforts to make graphene nanoribbons employed a metal substrate that hindered the ribbons’ useful electronic properties.

Now, scientists at ORNL and North Carolina State University report in the journal Nature Communications that they are the first to grow graphene nanoribbons without a metal substrate. Instead, they injected charge carriers that promote a chemical reaction that converts a polymer precursor into a graphene nanoribbon. At selected sites, this new technique can create interfaces between materials with different electronic properties. Such interfaces are the basis of semiconductor electronic devices from integrated circuits and transistors to light-emitting diodes and solar cells.

“Graphene is wonderful, but it has limits,” said Li. “In wide sheets, it doesn’t have an energy gap–an energy range in a solid where no electronic states can exist. That means you cannot turn it on or off.”

When a voltage is applied to a sheet of graphene in a device, electrons flow freely as they do in metals, severely limiting graphene’s application in digital electronics.

“When graphene becomes very narrow, it creates an energy gap,” Li said. “The narrower the ribbon is, the wider is the energy gap.”

In very narrow graphene nanoribbons, with a width of a nanometer or even less, how structures terminate at the edge of the ribbon is important too. For example, cutting graphene along the side of a hexagon creates an edge that resembles an armchair; this material can act like a semiconductor. Excising triangles from graphene creates a zigzag edge–and a material with metallic behavior.

To grow graphene nanoribbons with controlled width and edge structure from polymer precursors, previous researchers had used a metal substrate to catalyze a chemical reaction. However, the metal substrate suppresses useful edge states and shrinks the desired band gap.

Li and colleagues set out to get rid of this troublesome metal substrate. At the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL, they used the tip of a scanning tunneling microscope to inject either negative charge carriers (electrons) or positive charge carriers (“holes”) to try to trigger the key chemical reaction. They discovered that only holes triggered it. They were subsequently able to make a ribbon that was only seven carbon atoms wide–less than one nanometer wide–with edges in the armchair conformation.

“We figured out the fundamental mechanism, that is, how charge injection can lower the reaction barrier to promote this chemical reaction,” Li said. Moving the tip along the polymer chain, the researchers could select where they triggered this reaction and convert one hexagon of the graphene lattice at a time.

Next, the researchers will make heterojunctions with different precursor molecules and explore functionalities. They are also eager to see how long electrons can travel in these ribbons before scattering, and will compare it with a graphene nanoribbon made another way and known to conduct electrons extremely well. Using electrons like photons could provide the basis for a new electronic device that could carry current with virtually no resistance, even at room temperature.

“It’s a way to tailor physical properties for energy applications,” Li said. “This is an excellent example of direct writing. You can direct the transformation process at the molecular or atomic level.” Plus, the process could be scaled up and automated.

Researchers at North Carolina State University have developed a technique for converting positively charged (p-type) reduced graphene oxide (rGO) into negatively charged (n-type) rGO, creating a layered material that can be used to develop rGO-based transistors for use in electronic devices.

“Graphene is extremely conductive, but is not a semiconductor; graphene oxide has a bandgap like a semiconductor, but does not conduct well at all — so we created rGO,” says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and corresponding author of a paper describing the work. “But rGO is p-type, and we needed to find a way to make n-type rGO. And now we have it for next-generation, two-dimensional electronic devices.”

Specifically, Narayan and Anagh Bhaumik — a Ph.D. student in his lab — demonstrated two things in this study. First, they were able to integrate rGO onto sapphire and silicon wafers — across the entire wafer.

Second, the researchers used high-powered laser pulses to disrupt chemical groups at regular intervals across the wafer. This disruption moved electrons from one group to another, effectively converting p-type rGO to n-type rGO. The entire process is done at room temperature and pressure using high-power nanosecond laser pulses, and is completed in less than one-fifth of a microsecond. The laser radiation annealing provides a high degree of spatial and depth control for creating the n-type regions needed to create p-n junction-based two-dimensional electronic devices.

The end result is a wafer with a layer of n-type rGO on the surface and a layer of p-type rGO underneath.

This is critical, because the p-n junction, where the two types meet, is what makes the material useful for transistor applications.