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Purdue researchers have discovered a new two-dimensional material, derived from the rare element tellurium, to make transistors that carry a current better throughout a computer chip.

Purdue researchers Wenzhuo Wu and Peide Ye recently discovered tellurene, a two-dimensional material they manufactured in a solution, that has what it takes to make high-speed electronics faster. Credit: Purdue University image/Vincent Walter

The discovery adds to a list of extremely thin, two-dimensional materials that engineers have tried to use for improving the operation speed of a chip’s transistors, which then allows information to be processed faster in electronic devices, such as phones and computers, and defense technologies like infrared sensors.

Other two-dimensional materials, such as graphene, black phosphorus and silicene, have lacked either stability at room temperature or the feasible production approaches required to nanomanufacture effective transistors for higher speed devices.

“All transistors need to send a large current, which translates to high-speed electronics,” said Peide Ye, Purdue’s Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering. “One-dimensional wires that currently make up transistors have very small cross sections. But a two-dimensional material, acting like a sheet, can send a current over a wider surface area.”

Tellurene, a two-dimensional film researchers found in the element tellurium, achieves a stable, sheet-like transistor structure with faster-moving “carriers” – meaning electrons and the holes they leave in their place. Despite tellurium’s rarity, the pros of tellurene would make transistors made from two-dimensional materials easier to produce on a larger scale. The researchers detail their findings in Nature Electronics.

“Even though tellurium is not abundant on the Earth’s crust, we only need a little bit to be synthesized through a solution method. And within the same batch, we have a very high production yield of two-dimensional tellurene materials,” said Wenzhuo Wu, assistant professor in Purdue’s School of Industrial Engineering. “You simply scale up the container that holds the solution, so productivity is high.”

Since electronics are typically in use at room temperature, naturally stable tellurene transistors at this temperature are more practical and cost-effective than other two-dimensional materials that have required a vacuum chamber or low operation temperature to achieve similar stability and performance.

The larger crystal flakes of tellurene also mean less barriers between flakes to electron movement – an issue with the more numerous, smaller flakes of other two-dimensional materials.

“High carrier mobility at room temperature means more practical applications,” Ye said. Faster-moving electrons and holes then lead to higher currents across a chip.

The researchers anticipate that because tellurene can grow on its own without the help of any other substance, the material could possibly find use in other applications beyond computer chip transistors, such as flexible printed devices that convert mechanical vibrations or heat to electricity.

“Tellurene is a multifunctional material, and Purdue is the birthplace for this new material,” Wu said. “In our opinion, this is much closer to the scalable production of two-dimensional materials with controlled properties for practical technologies.”

An international research team led by physicists at the Technical University of Munich (TUM) has developed molecules that can be switched between two structurally different states using an applied voltage. Such nanoswitches can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

A research team at the Technical University of Munich has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules. Credit: Yuxiang Gong / TUM / Journal of the American Chemical Society

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative effort, a team of physicists at the Technical University of Munich has successfully deployed a single molecule as a switching element for light signals.

“Switching with just a single molecule brings future electronics one step closer to the ultimate limit of miniaturization,” says nanoscientist Joachim Reichert from the Physics Department of the Technical University of Munich.

Different structure – different optical properties

The team initially developed a method that allowed them to create precise electrical contacts with molecules in strong optical fields and to control them using an applied voltage. At a potential difference of around one volt, the molecule changes its structure: It becomes flat, conductive and scatters light.

This optical behavior, which differs depending on the structure of the molecule, is quite exciting for the researchers because the scattering activity – Raman scattering, in this case – can be both observed and, at the same time, switched on and off via an applied voltage.

Challenging technology

The researchers used molecules synthesized by teams based in Basel and Karlsruhe. The molecules can change their structure in specific ways when they are charged. They are arranged on a metal surface and contacted using the corner of a glass fragment with a very thin metal coating as a tip..

This serves as an electrical contact, light source and light collector, all in one. The researchers used the fragment to direct laser light to the molecule and measure tiny spectroscopic signals that vary with the applied voltage.

Contacting individual molecules electrically is extremely challenging from a technical point of view. The scientists have now successfully combined this procedure with single-molecule spectroscopy, allowing them to observe even the smallest structural changes in molecules with great precision.

Competition for silicon

One goal of molecular electronics is to develop novel devices that can replace traditional silicon-based components using integrated and directly controllable molecules.

Thanks to its tiny dimensions, this nanosystem is suitable for applications in optoelectronics, in which light needs to be switched using variations in electrical potential.

Scientists at the Center for Functional Nanomaterials (CFN)–a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory–have used an optoelectronic imaging technique to study the electronic behavior of atomically thin nanomaterials exposed to light. Combined with nanoscale optical imaging, this scanning photocurrent microscopy technique provides a powerful tool for understanding the processes affecting the generation of electrical current (photocurrent) in these materials. Such an understanding is key to improving the performance of solar cells, optical sensors, light-emitting diodes (LEDs), and other optoelectronics–electronic devices that rely on light-matter interactions to convert light into electrical signals or vice versa.

“Anyone who wants to know how light-induced electrical current is distributed across a semiconductor will benefit from this capability,” said CFN materials scientist Mircea Cotlet, co-corresponding author on the May 17 Advanced Functional Materials paper describing the work.

Generating an electrical current

When hit with light, semiconductors (materials that have an electrical resistance in between that of metals and insulators) generate an electric current. Semiconductors that consist of one layer or a few layers of atoms–for example, graphene, which has a single layer of carbon atoms–are of particular interest for next-generation optoelectronics because of their sensitivity to light, which can controllably alter their electrical conductivity and mechanical flexibility. However, the amount of light that atomically thin semiconductors can absorb is limited, thus limiting the materials’ response to light.

To enhance the light-harvesting properties of these two-dimensional (2D) materials, scientists add tiny (10-50 atoms in diameter) semiconducting particles called quantum dots in the layer(s). The resulting “hybrid” nanomaterials not only absorb more light but also have interactions occurring at the interface where the two components meet. Depending on their size and composition, the light-excited quantum dots will transfer either charge or energy to the 2D material. Knowing how these two processes influence the photocurrent response of the hybrid material under different optical and electrical conditions–such as the intensity of the incoming light and applied voltage–is important to designing optoelectronic devices with properties tailored for particular applications.

“Photodetectors sense an extremely low level of light and convert that light into an electrical signal,” explained Cotlet. “On the other hand, photovoltaic devices such as solar cells are made to absorb as much light as possible to produce an electrical current. In order to design a device that operates for photodetection or photovoltaic applications, we need to know which of the two processes–charge or energy transfer–is beneficial.”

Lighting up charge and energy transfer processes

In this study, the CFN scientists combined atomically thin molybdenum disulfide with quantum dots. Molybdenum disulfide is one of the transition-metal dichalcogenides, semiconducting compounds with a transition-metal (in this case, molybdenum) layer sandwiched between two thin layers of a chalcogen element (in this case, sulfur). To control the interfacial interactions, they designed two kinds of quantum dots: one with a composition that favors charge transfer and the other with a composition that favors energy transfer.

“Both kinds have cadmium selenide at their core, but one of the cores is surrounded by a shell of zinc sulfide,” explained CFN research associate and first author Mingxing Li. “The shell is a physical spacer that prevents charge transfer from happening. The core-shell quantum dots promote energy transfer, whereas the core-only quantum dots promote charge transfer.”

The scientists used the clean room in the CFN Nanofabrication Facility to make devices with the hybrid nanomaterials. To characterize the performance of these devices, they conducted scanning photocurrent microscopy studies with an optical microscope built in-house using existing equipment and the open-source GXSM instrument control software developed by CFN physicist and co-author Percy Zahl. In scanning photocurrent microscopy, a laser beam is scanned across the device while the photocurrent is measured at different points. All of these points are combined to produce an electrical current “map.” Because charge and energy transfer have distinct electrical signatures, scientists can use this technique to determine which process is behind the observed photocurrent response.

The maps in this study revealed that the photocurrent response was highest at low light exposure for the core-only hybrid device (charge transfer) and at high light exposure for the core-shell hybrid device (energy transfer). These results suggest that charge transfer is extremely beneficial to the device functioning as a photodetector, and energy transfer is preferred for photovoltaic applications.

“Distinguishing energy and charge transfers solely by optical techniques, such as photoluminescence lifetime imaging microscopy, is challenging because both processes reduce luminescence lifetime to similar degrees,” said CFN materials scientist and co-corresponding author Chang-Yong Nam. “Our investigation demonstrates that optoelectronic measurements combining localized optical excitation and photocurrent generation can not only clearly identify each process but also suggest potential optoelectronic device applications suitable to each case.”

“At the CFN, we conduct experiments to study how nanomaterials function under real operating conditions,” said Cotlet. “In this case, we combined the optical expertise of the Soft and Bio Nanomaterials Group, device fabrication and electrical characterization expertise of the Electronic Nanomaterials Group, and software expertise of the Interface Science and Catalysis Group to develop a capability at the CFN that will enable scientists to study optoelectronic processes in a variety of 2D materials. The new scanning photocurrent microscopy facility is now open to CFN users, and we hope this capability will draw more users to the CFN fabrication and characterization facilities to study and improve the performance of optoelectronic devices.”

GLOBALFOUNDRIES today announced that its 22nm FD-SOI (22FDX®) technology platform has been certified to AEC-Q100 Grade 2 for production. As the industry’s most advanced automotive-qualified FD-SOI process technology, GF’s 22FDX platform includes a comprehensive set of technology and design enablement capabilities tailored to improve the performance and power efficiency of automotive integrated circuits (ICs) while maintaining adherence to strict automotive safety and quality standards.

With the rapid proliferation of automotive electronics content and regulations on energy efficiency and safety, semiconductor device component quality and reliability are more critical than ever. As a part of the AEC-Q100 certification, devices must successfully withstand reliability stress tests for an extended period of time, over a wide temperature range in order to achieve Grade 2 certification. The qualification of GF’s 22FDX process exemplifies the company’s commitment to providing high-performance, high-quality technology solutions for the automotive industry.

“FD-SOI has advantages for companies who are looking for real-time trade-offs in power, performance and cost,” said Dan Hutcheson, CEO and Chairman of VLSI Research. “GF’s automotive-qualified 22FDX technology is exactly what automakers and suppliers need to enable the rapid integration of highly integrated automotive-grade ICs.”

“GLOBALFOUNDRIES has more than 10 years of providing automotive solutions to the industry. We have proven our commitment to semiconductor quality and reliability through a range of certifications and audits every year,” said Dr. Bami Bastani, senior vice president of business units at GF. “The automotive qualification of our 22FDX technology reaffirms our commitment to expanding our FD-SOI capabilities and portfolio to reach new markets and customers. We now have a proven ability to manufacture our 22FDX technology to meet the rigorous quality and performance requirements of the automotive market.”

As a part of the company’s AutoPro™ platform, 22FDX allows customers to easily migrate their automotive microcontrollers and ASSPs to a more advanced technology, while leveraging the significant area, performance and energy efficiency benefits over competing technologies. Moreover, the optimized platform offers high performance RF and mmWave capabilities for automotive radar applications and supports implementation of logic, Flash, non-volatile memory (NVM) in MCUs and high voltage devices to meet the unique requirements of in-vehicle ICs.

GF’s AutoPro platform consists of a broad portfolio of automotive AEC-Q100 qualified technology solutions, backed by robust services package that comply with rigorous ISO automotive quality standards across GF’s fabs in Singapore and, most recently, Fab 1 in Dresden, Germany that achieved ISO-9001/IATF-16949 certification and is now capable of meeting the stringent and evolving needs of the automotive industry.

The 22FDX PDK is available now along with a wide-range of silicon-proven IP. Customers can now start optimizing their chip designs to develop differentiated low power and high performance automotive solutions.

Technology trends in backplane technology are driving higher gas demand in display manufacturing. Specific gas requirements of process blocks are discussed, and various supply modes are reviewed.

BY EDDIE LEE, Linde Electronics, Hsinchu, Taiwan

Since its initial communalization in the 1990s, active matrix thin-film-transistor (TFT) displays have become an essential and indispensable part of modern living. They are much more than just televisions and smartphones; they are the primary communication and information portals for our day-to- day life: watches (wearables), appliances, advertising, signage, automobiles and more.

There are many similarities in the display TFT manufacturing and semiconductor device manufacturing such as the process steps (deposition, etch, cleaning, and doping), the type of gases used in these steps, and the fact that both display and semiconductor manufacturing both heavily use gases.

However, there are technology drivers and manufacturing challenges that differentiate the two. For semiconductor device manufacturing, there are technology limitations in making the device increasingly smaller. For display manufacturing, the challenge is primarily maintaining the uniformity of glass as consumers drive the demand for larger and thinner displays.

While semiconductor wafer size has maxed because of the challenges of making smaller features uniformly across the surface of the wafer, the size of the display mother glass has grown from 0.1m x 0.1m with 1.1mm thickness to 3m x 3m with 0.5mm thickness over the past 20 years due to consumer demands for larger, lighter, and more cost-effective devices.

As the display mother glass area gets bigger and bigger,so does the equipment used in the display manufacturing process and the volume of gases required. In addition, the consumer’s desire for a better viewing experience such as more vivid color, higher resolution, and lower power consumption has also driven display manufacturers to develop and commercialize active matrix organic light emitting displays (AMOLED).

Technology

Layers of display device

In general, there are two types of displays in the market today: active matrix liquid crystal display (AMLCD) and AMOLED. In its simplicity, the fundamental components required to make up the display are the same for AMLCD and AMOLED. There are four layers of a display device (FIGURE 1): a light source, switches that are the thin-film-transistor and where the gases are mainly used, a shutter to control the color selection, and the RGB (red, green, blue) color filter.

About backplane/TFT

The thin-film-transistors used for display are 2D transitional transistors, which are similar to bulk CMOS before FinFET. For the active matrix display, there is one transistor for each pixel to drive the individual RGB within the pixel. As the resolution of the display grows, the transistor size also reduces, but not to the sub-micron scale of semiconductor devices. For the 325 PPI density, the transistor size is approximately 0.0001 mm2 and for the 4K TV with 80 PPI density, the transistor size is approximately 0.001 mm2.

Technology trends TFT-LCD (thin-film-transistor liquid-crystal display) is the baseline technology. MO / White OLED (organic light emitting diode) is used for larger screens. LTPS / AMOLED is used for small / medium screens. The challenges for OLED are the effect of < 1 micron particles on yield, much higher cost compared to a-Si due to increased mask steps, and moisture impact to yield for the OLED step.

Mobility limitation (FIGURE 2) is one of the key reasons for the shift to MO and LTPS to enable better viewing experience from higher resolution, etc.

The challenge to MO is the oxidation after IGZO metalization / moisture prevention after OLED step, which decreases yield. A large volume of N2O (nitrous oxide) is required for manufacturing, which means a shift in the traditional supply mode might need to be considered.

Although AMLCD displays are still dominant in the market today, AMOLED displays are growing quickly. Currently about 25% of smartphones are made with AMOLED displays and this is expected to grow to ~40% by 2021. OLED televisions are also growing rapidly, enjoying double digit growth rate year over year. Based on IHS data, the revenue for display panels with AMOLED technol- ogies is expected to have a CAGR of 18.9% in the next five years while the AMLCD display revenue will have a -2.8% CAGR for the same period with the total display panel revenue CAGR of 2.5%. With the rapid growth of AMOLED display panels, the panel makers have accel- erated their investment in the equipment to produce AMOLED panels.

Types of backplanes

There are three types of thin-film-transistor devices for display: amorphous silicon (a-Si), low temperature polysilicon (LTPS), and metal oxide (MO), also known as transparent amorphous oxide semiconductor (TAOS). AMLCD panels typically use a-Si for lower-resolution displays and TVs while high-resolution displays use LTPS transistors, but this use is mainly limited to small and medium displays due to its higher costs and scalability limitations. AMOLED panels use LTPS and MO transistors where MO devices are typically used for TV and large displays (FIGURE 3).

How gases are used

This shift in technology also requires a change in the gases used in production of AMOLED panels as compared with the AMLCD panels. As shown in FIGURE 4, display manufacturing today uses a wide variety of gases.

These gases can be categorized into two types: Electronic Specialty gases (ESGs) and Electronic Bulk gases (EBGs) (FIGURE 5). Electronic Specialty gases such as silane, nitrogen trifluoride, fluorine (on-site generation), sulfur hexafluoride, ammonia, and phosphine mixtures make up 52% of the gases used in the manufacture of the displays while the Electronic Bulk gases–nitrogen, hydrogen, helium, oxygen, carbon dioxide, and argon – make up the remaining 48% of the gases used in the display manufacturing.

Key usage drivers

The key ga susage driver in the manufacturing of displays is PECVD (plasma-enhanced chemical vapor deposition), which accounts for 75% of the ESG spending, while dry etch is driving helium usage. LTPS and MO transistor production is driving nitrous oxide usage. The ESG usage for MO transistor production differs from what is shown in FIGURE 4: nitrous oxide makes up 63% of gas spend, nitrogen trifluoride 26%, silane 7%, and sulfur hexafluoride and ammonia together around 4%. Laser gases are used not only for lithography, but also for excimer laser annealing application in LTPS.

Silane: SiH4 is one of the most critical molecules in display manufacturing. It is used in conjunction with ammonia (NH3) to create the silicon nitride layer for a-Si transistor, with nitrogen (N2) to form the pre excimer laser anneal a-Si for the LTPS transistor, or with nitrous oxide (N2O) to form the silicon oxide layer of MO transistor.

Nitrogen trifluoride: NF3 is the single largest electronic material from spend and volume standpoint for a-Si and LTPS display production while being surpassed by N2O for MO production. NF3 is used for cleaning the PECVD chambers. This gas requires scalability to get the cost advantage necessary for the highly competitive market.

Nitrous oxide: Used in both LTPS and MO display production, N2O has surpassed NF3 to become the largest electronic material from spend and volume standpoint for MO production. N2O is a regional and localized product due to its low cost, making long supply chains with high logistic costs unfeasible. Averaging approximately 2 kg per 5.5 m2 of mother glass area, it requires around 240 tons per month for a typical 120K per month capacity generation 8.5 MO display production. The largest N2O compressed gas trailer can only deliver six tons of N2O each time and thus it becomes both costly and risky
for MO production.

Nitrogen: For a typical large display fab, N2 demand can be as high as 50,000 Nm3/hour, so an on-site generator, such as the Linde SPECTRA-N® 50,000, is a cost-effective solution that has the added benefit of an 8% reduction in CO2 (carbon dioxide) footprint over conventional nitrogen plants.

Helium: H2 is used for cooling the glass during and after processing. Manufacturers are looking at ways to decrease the usage of helium because of cost and availability issues due it being a non-renewable gas.

Gas distribution at the fab

N2 On-site generators: Nitrogen is the largest consumed gas at the fab, and is required to be available before the first tools are brought to the fab. Like major semiconductor fabs, large display fabs require very large amounts of nitrogen, which can only be economically supplied by on-site plants.

Cryogenic liquid truck trailers: Oxygen, argon, and carbon dioxide are produced at off-site plants and trucked short distances as cryogenic liquids in specialty vacuum-insulated tankers.
Compressed gas truck trailers: Other large volume gases like hydrogen and helium are supplied over longer distances in truck or ISO-sized tanks as compressed gases.

Individual packages: Specialty gases are supplied in individual packages. For higher volume materials like silane and nitrogen trifluoride, these can be supplied in large ISO packages holding up to 10 tons. Materials with smaller requirements are packaged in standard gas cylinders.

Blended gases: Laser gases and dopants are supplied as blends of several different gases. Both the accuracy and precision of the blended products are important to maintain the display device fabrication operating within acceptable parameters.

In-fab distribution: Gas supply does not end with the delivery or production of the material of the fab. Rather, the materials are further regulated with additional filtration, purification, and on-line analysis before delivery to individual production tools.

Conclusion

The consumer demand for displays that offer increas- ingly vivid color, higher resolution, and lower power consumption will challenge display makers to step up the technologies they employ and to develop newer displays such as flexible and transparent displays. The transistors to support these new displays will either be LTPS and / or MO, which means the gases currently being used in these processes will continue to grow. Considering the current a-Si display production, the gas consumption per area of the glass will increase by 25% for LTPS and ~ 50% for MO productions.

To facilitate these increasing demands, display manufacturers must partner with gas suppliers to identify which can meet their technology needs, globally source electronic materials to provide customers with stable and cost- effective gas solutions, develop local sources of electronic materials, improve productivity, reduce carbon footprint, and increase energy efficiency through on-site gas plants. This is particularly true for the burgeoning China display manufacturing market, which will benefit from investing in on-site bulk gas plants and collaboration with global materials suppliers with local production facilities for high-purity gas and chemical manufacturing.

Inorganic semiconductors such as silicon are indispensable in modern electronics because they possess tunable electrical conductivity between that of a metal and that of an insulator. The electrical conductivity of a semiconductor is controlled by its band gap, which is the energy difference between its valence and conduction bands; a narrow band gap results in increased conductivity because it is easier for an electron to move from the valence to the conduction band. However, inorganic semiconductors are brittle, which can lead to device failure and limits their application range, particularly in flexible electronics.

Inorganic semiconducting crystals generally tend to fail in a brittle manner. This is true for zinc sulfide (ZnS); ZnS crystals (A) show catastrophic fracture after mechanical tests under ordinary light-exposure environments (B). However, we found out that ZnS crystals can be plastically deformed up to a deformation strain of εt = 45 % when deformed along the [001] direction in complete darkness even at room temperature (C). Moreover, the optical band gap of the deformed ZnS crystals decreased by 0.6 eV after deformation. Credit: Atsutomo Nakamura

Inorganic semiconducting crystals generally tend to fail in a brittle manner. This is true for zinc sulfide (ZnS); ZnS crystals (A) show catastrophic fracture after mechanical tests under ordinary light-exposure environments (B). However, we found out that ZnS crystals can be plastically deformed up to a deformation strain of εt = 45 % when deformed along the [001] direction in complete darkness even at room temperature (C). Moreover, the optical band gap of the deformed ZnS crystals decreased by 0.6 eV after deformation. Credit: Atsutomo Nakamura

A group at Nagoya University recently discovered that an inorganic semiconductor behaved differently in the dark compared with in the light. They found that crystals of zinc sulfide (ZnS), a representative inorganic semiconductor, were brittle when exposed to light but flexible when kept in the dark at room temperature. The findings were published in Science.

“The influence of complete darkness on the mechanical properties of inorganic semiconductors had not previously been investigated,” study coauthor Atsutomo Nakamura says. “We found that ZnS crystals in complete darkness displayed much higher plasticity than those under light exposure.”

The ZnS crystals in the dark deformed plastically without fracture until a large strain of 45%. The team attributed the increased plasticity of the ZnS crystals in the dark to the high mobility of dislocations in complete darkness. Dislocations are a type of defect found in crystals and are known to influence crystal properties. Under light exposure, the ZnS crystals were brittle because their deformation mechanism was different from that in the dark.

The high plasticity of the ZnS crystals in the dark was accompanied by a considerable decrease in the band gap of the deformed crystals. Thus, the band gap of ZnS crystals and in turn their electrical conductivity may be controlled by mechanical deformation in the dark. The team proposed that the decreased band gap of the deformed crystals was caused by deformation introducing dislocations into the crystals, which changed their band structure.

“This study reveals the sensitivity of the mechanical properties of inorganic semiconductors to light,” coauthor Katsuyuki Matsunaga says. “Our findings may allow development of technology to engineer crystals through controlled light exposure.”

The researchers’ results suggest that the strength, brittleness, and conductivity of inorganic semiconductors may be regulated by light exposure, opening an interesting avenue to optimize the performance of inorganic semiconductors in electronics.

Pure quartz glass is highly transparent and resistant to thermal, physical, and chemical impacts. These are optimum prerequisites for use in optics, data technology or medical engineering. For efficient, high-quality machining, however, adequate processes are lacking. Scientists of Karlsruhe Institute of Technology (KIT) have developed a forming technology to structure quartz glass like a polymer. This innovation is reported in the journal Advanced Materials.

“It has always been a big challenge to combine highly pure quartz glass and its excellent properties with a simple structuring technology,” says Dr. Bastian E. Rapp, Head of the NeptunLab interdisciplinary research group of KIT’s Institute of Microstructure Technology (IMT). Rapp and his team develop new processes for industrial glass processing. “Instead of heating glass up to 800 °C for forming or structuring parts of glass blocks by laser processing or etching, we start with the smallest glass particles,” says the mechanical engineer. The scientists mix glass particles of 40 nanometers in size with a liquid polymer, form the mix like a sponge cake, and harden it to a solid by heating or light exposure. The resulting solid consists of glass particles in a matrix at a ratio of 60 to 40 vol%. The polymers act like a bonding agent that retains the glass particles at the right locations and, hence, maintains the shape.

This “Glassomer” can be milled, turned, laser-machined or processed in CNC machines just like a conventional polymer. “The entire range of polymer forming technologies is now opened for glass,” Rapp emphasizes. For fabricating high-performance lenses that are used in smartphones among others, the scientists produce a Glassomer rod, from which the lenses are cut. For highly pure quartz glass, the polymers in the composite have to be removed. For doing so, the lenses are heated in a furnace at 500 to 600 °C and the polymer is burned fully to CO2. To close the resulting gaps in the material, the lenses are sintered at 1300 °C. During this process, the remaining glass particles are densified to pore-free glass.

This forming technology enables production of highly pure glass materials for any applications, for which only polymers have been suited so far. This opens up new opportunities for the glass processing industry as well as for the optical industry, microelectronics, biotechnology, and medical engineering. “Our process is suited for mass production. Production and use of quartz glass are much cheaper, more sustainable, and more energy-efficient than those of a special polymer,” Rapp explains.

This is the third innovation for the processing of quartz glass that has been developed by NeptunLab on the basis of a liquid glass-polymer mixture. In 2016, the scientists already succeeded in using this mixture for molding. In 2017, they applied the mixture for 3D printing and demonstrate its suitability for additive manufacture. Within the framework of the “NanomatFutur” competition for early-stage researchers, the team was funded with EUR 2.8 million by the Federal Ministry of Education and Research from 2014 to 2018. A spinoff now plans to commercialize Glassomer.

Among the chief complaints for smartphone, laptop and other battery-operated electronics users is that the battery life is too short and–in some cases–that the devices generate heat. Now, a group of physicists led by Deepak K. Singh, associate professor of physics and astronomy at the University of Missouri, has developed a device material that can address both issues. The team has applied for a patent for a magnetic material that employs a unique structure–a “honeycomb” lattice that exhibits distinctive electronic properties.

The left shows the atomic force micrograph, exhibiting honeycomb structure pattern behind a magnetic device. Inset shows the schematic of current flow direction. On the right: electrical data reveals diode-type behavior of current flowing in one direction. Inset shows that the dissipative power is of the order of nano-watt in the current flowing direction, which is at least three orders of magnitude smaller than the semiconductor diode. Credit: Deepak Singh

The left shows the atomic force micrograph, exhibiting honeycomb structure pattern behind a magnetic device. Inset shows the schematic of current flow direction. On the right: electrical data reveals diode-type behavior of current flowing in one direction. Inset shows that the dissipative power is of the order of nano-watt in the current flowing direction, which is at least three orders of magnitude smaller than the semiconductor diode. Credit: Deepak Singh

“Semiconductor diodes and amplifiers, which often are made of silicon or germanium, are key elements in modern electronic devices,” said Singh, who also serves as the principal investigator of the Magnetism and Superconductivity Research Laboratory at MU. “A diode normally conducts current and voltage through the device along only one biasing direction, but when the voltage is reversed, the current stops. This switching process costs significant energy due to dissipation, or the depletion of the power source, thus affecting battery life. By substituting the semiconductor with a magnetic system, we believed we could create an energetically effective device that consumes much less power with enhanced functionalities.”

Singh’s team developed a two-dimensional, nanostructured material created by depositing a magnetic alloy, or permalloy, on the honeycomb structured template of a silicon surface. The new material conducts unidirectional current, or currents that only flow one way. The material also has significantly less dissipative power compared to a semiconducting diode, which is normally included in electronic devices.

The magnetic diode paves the way for new magnetic transistors and amplifiers that dissipate very little power, thus increasing the efficiency of the power source. This could mean that designers could increase the life of batteries by more than a hundred-fold. Less dissipative power in computer processors could also reduce the heat generated in laptop or desktop CPUs.

“Although more works need to be done to develop the end product, the device could mean that a normal 5-hour charge could increase to more than a 500-hour charge,” Singh said. “The device could also act as an ‘on/off switch’ for other periphery components such as closed-circuit cameras or radio frequency attenuators, which reduces power flowing through a device. We have applied for a U.S. patent and have begun the process of incorporating a spin-off company to help us take the device to market.”

The proposed startup company associated with this research, highlights the university’s impact on the state’s economic development efforts, including commercialization of research conducted at Mizzou, workforce development and job growth, quality of life improvements for residents, and attracting corporations and businesses to the state. Companies commercializing MU technologies have secured hundreds of millions of dollars in investments and grants to advance their commercialization efforts. In 2017, the Office of Technology Management and Industry Relations reported that 31 U.S. patents were issued to members of the MU community.

A Columbia University-led international team of researchers has developed a technique to manipulate the electrical conductivity of graphene with compression, bringing the material one step closer to being a viable semiconductor for use in today’s electronic devices.

By compressing layers of boron nitride and graphene, researchers were able to enhance the material's band gap, bringing it one step closer to being a viable semiconductor for use in today's electronic devices. Credit: Philip Krantz

By compressing layers of boron nitride and graphene, researchers were able to enhance the material’s band gap, bringing it one step closer to being a viable semiconductor for use in today’s electronic devices. Credit: Philip Krantz

“Graphene is the best electrical conductor that we know of on Earth,” said Matthew Yankowitz, a postdoctoral research scientist in Columbia’s physics department and first author on the study. “The problem is that it’s too good at conducting electricity, and we don’t know how to stop it effectively. Our work establishes for the first time a route to realizing a technologically relevant band gap in graphene without compromising its quality. Additionally, if applied to other interesting combinations of 2D materials, the technique we used may lead to new emergent phenomena, such as magnetism, superconductivity, and more.”

The study, funded by the National Science Foundation and the David and Lucille Packard Foundation, appears in the May 17 issue of Nature.

The unusual electronic properties of graphene, a two-dimensional (2D) material comprised of hexagonally-bonded carbon atoms, have excited the physics community since its discovery more than a decade ago. Graphene is the strongest, thinnest material known to exist. It also happens to be a superior conductor of electricity – the unique atomic arrangement of the carbon atoms in graphene allows its electrons to easily travel at extremely high velocity without the significant chance of scattering, saving precious energy typically lost in other conductors.

But turning off the transmission of electrons through the material without altering or sacrificing the favorable qualities of graphene has proven unsuccessful to-date.

“One of the grand goals in graphene research is to figure out a way to keep all the good things about graphene but also create a band gap – an electrical on-off switch,” said Cory Dean, assistant professor of physics at Columbia University and the study’s principal investigator. He explained that past efforts to modify graphene to create such a band gap have degraded the intrinsically good properties of graphene, rendering it much less useful. One superstructure does show promise, however. When graphene is sandwiched between layers of boron nitride (BN), an atomically-thin electrical insulator, and the two materials are rotationally aligned, the BN has been shown to modify the electronic structure of the graphene, creating a band gap that allows the material to behave as a semiconductor – that is, both as an electrical conductor and an insulator. The band gap created by this layering alone, however, is not large enough to be useful in the operation of electrical transistor devices at room temperature.

In an effort to enhance this band gap, Yankowitz, Dean, and their colleagues at the National High Magnetic Field Laboratory, the University of Seoul in Korea, and the National University of Singapore, compressed the layers of the BN-graphene structure and found that applying pressure substantially increased the size of the band gap, more effectively blocking the flow of electricity through the graphene.

“As we squeeze and apply pressure, the band gap grows,” Yankowitz said. “It’s still not a big enough gap – a strong enough switch – to be used in transistor devices at room temperature, but we have gained a fundamentally better understanding of why this band gap exists in the first place, how it can be tuned, and how we may target it in the future. Transistors are ubiquitous in our modern electronic devices, so if we can find a way to use graphene as a transistor it would have widespread applications.”

Yankowitz added that scientists have been conducting experiments at high pressures in conventional three-dimensional materials for years, but no one had yet figured out a way to do them with 2D materials. Now, researchers will be able to test how applying various degrees of pressure changes the properties of a vast range of combinations of stacked 2D materials.

“Any emergent property that results from the combination of 2D materials should grow stronger as the materials are compressed,” Yankowitz said. “We can take any of these arbitrary structures now and squeeze them and the strength of the resulting effect is tunable. We’ve added a new experimental tool to the toolbox we use to manipulate 2D materials and that tool opens boundless possibilities for creating devices with designer properties.”

EV Group (EVG), a supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, today announced that it has received an order for its EVG®120 automated resist processing system from VTT Technical Research Centre of Finland (VTT). An existing customer of EVG’s wafer bonding and alignment systems, VTT is among the first to place an order for the newest version of the EVG120 system, which has been enhanced to provide even greater reliability, throughput and process performance compared to the previous-generation platform. VTT will use the new EVG120 system to increase capacity for supporting parallel R&D projects involving new and different coating materials, as well as to enable new research applications in “More than Moore” technology areas such as MEMS, optoelectronics, photonics and compound semiconductors.

“Lithography plays a vital role in the production process for devices that power our digital society,” stated Heini Saloniemi, manager, process engineering, at VTT. “After a thorough product evaluation of lithography coating systems, VTT selected the EVG120 in a competitive tender, with coating uniformity and repeatability of coating thickness among the key evaluation criteria. We look forward to receiving the new EVG120 system, which will enhance our lithography process capabilities and allow us to explore new avenues of research.”

The EVG120 automated resist processing system provides reliable and high-quality coating and developing processes in a universal platform. Its versatility and flexibility, as well as its low cost of ownership, makes it an ideal system for research environments where many development projects may be running in parallel, while its high throughput rates enable its use in volume production.

The updated EVG120 platform maintains all industry-leading capabilities of the previous-generation platform, including: compact design for minimal footprint; customizable module configurations for spin and spray coating, developing, bake and chill; EVG’s CoverSpin™ technology, which provides optimized coating uniformity of odd-shaped and square substrates; EVG’s proprietary OmniSpray® technology for conformal coating of extreme topographies; and wafer-edge handling.

The EVG®120 automated resist processing system from EV Group provides reliable and high-quality coating and developing processes in a universal platform.

The EVG®120 automated resist processing system from EV Group provides reliable and high-quality coating and developing processes in a universal platform.

New features on the updated platform include:

  • Separation of wet processing modules to enable constant conditions chamber to chamber
  • Integrated chemistry cabinet for resist pumps and bottles (including support for high-viscosity resists), for improved process control and short dispense cycles
  • New robot handling system that provides the highest reliability and increased throughput
  • Optional humidity and temperature control for constant environmental conditions

“As the leading research institute in Finland, VTT has a strong global network of industry partners throughout the world to transform breakthrough research into new products and services in renewable energy, health care, smart industry and smart city, as well as beyond. EVG is working tirelessly to support our key customers such as VTT in these endeavors,” stated Thomas Wagenleitner, product management director at EV Group. “As part of that effort, we have leveraged more than 20 years of experience in resist processing to drive continuous improvements to our industry benchmark EVG120 platform. This allows us to enable even greater levels of coating performance for our customers at a lower cost of ownership, which is critical for both production fabs and research labs at the cutting edge of technology like VTT.”