Category Archives: Process Materials

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

Scanning Electron Microscope Images of architectured carbon nanotube (CNT) textile made at Illinois. Colored schematic shows the architecture of self-weaved CNTs, and the inset shows a high resolution SEM of the inter-diffusion of CNT among the different patches due to capillary splicing. Credit: University of Illinois

Scanning Electron Microscope Images of architectured carbon nanotube (CNT) textile made at Illinois. Colored schematic shows the architecture of self-weaved CNTs, and the inset shows a high resolution SEM of the inter-diffusion of CNT among the different patches due to capillary splicing. Credit: University of Illinois

“The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including biological and structural health monitoring sensors,” explained Sameh Tawfick, an assistant professor of mechanical science and engineering at Illinois. “Aligned carbon nanotube sheets are suitable for a wide range of application spanning the micro- to the macro-scales including Micro-Electro-Mechanical Systems (MEMS), supercapacitor electrodes, electrical cables, artificial muscles, and multi-functional composites.

“To our knowledge, this is the first study to apply the principles of fracture mechanics to design and study the toughness nano-architectured CNT textiles. The theoretical framework of fracture mechanics is shown to be very robust for a variety of linear and non-linear materials.”

Carbon nanotubes, which have been around since the early nineties, have been hailed as a “wonder material” for numerous nanotechnology applications, and rightly so. These tiny cylindrical structures made from wrapped graphene sheets have diameter of a few nanometers–about 1000 times thinner than a human hair, yet, a single carbon nanotube is stronger than steel and carbon fibers, more conductive than copper, and lighter than aluminum.

However, it has proven really difficult to construct materials, such as fabrics or films that demonstrate these properties on centimeter or meter scales. The challenge stems from the difficulty of assembling and weaving CNTs since they are so small, and their geometry is very hard to control.

“The study of the fracture energy of CNT textiles led us to design these extremely tough films,” stated Yue Liang, a former graduate student with the Kinetic Materials Research group and lead author of the paper, “Tough Nano-Architectured Conductive Textile Made by Capillary Splicing of Carbon Nanotubes,” appearing in Advanced Engineering Materials. To our knowledge, this is the first study of the fracture energy of CNT textiles.

Beginning with catalyst deposited on a silicon oxide substrate, vertically aligned carbon nanotubes were synthesized via chemical vapor deposition in the form of parallel lines of 5μm width, 10μm length, and 20-60μm heights.

“The staggered catalyst pattern is inspired by the brick and mortar design motif commonly seen in tough natural materials such as bone, nacre, the glass sea sponge, and bamboo,” Liang added. “Looking for ways to staple the CNTs together, we were inspired by the splicing process developed by ancient Egyptians 5,000 years ago to make linen textiles. We tried several mechanical approaches including micro-rolling and simple mechanical compression to simultaneously re-orient the nanotubes, then, finally, we used the self-driven capillary forces to staple the CNTs together.”

“This work combines careful synthesis, and delicate experimentation and modeling,” Tawfick said. “Flexible electronics are subject to repeated bending and stretching, which could cause their mechanical failure. This new CNT textile, with simple flexible encapsulation in an elastomer matrix, can be used in smart textiles, smart skins, and a variety of flexible electronics. Owing to their extremely high toughness, they represent an attractive material, which can replace thin metal films to enhance device reliability.”

In addition to Liang and Tawfick, co-authors include David Sias and Ping Ju Chen.

Conax Technologies announced the acquisition of Quartz Engineering, a manufacturer of quartz sheaths for temperature sensors headquartered in Tempe, AZ. S. K. Choi, former President of Quartz engineering, will stay on and help with the integration of Quartz Engineering and Conax. Choi has 40 years of experience in the semiconductor segment of the quartz industry and 20 years of experience in the fabrication of the specific type of sheaths primarily used by Conax.

This acquisition represents a commitment to improving the company’s responsiveness and the quality of products the company can provide to customers in the semiconductor industry.

Conax Business Unit Manager Michael Ferraro stated, “We’re expanding our focus in the growing Semiconductor industry. Many of the temperature sensors used inside process chambers need a semiconductor-grade quartz sheath to protect them from the chemicals and temperatures present. With the acquisition of Quartz Engineering, we now have in-house capabilities to design and manufacture quartz sheaths for temperature sensors.”

Ferraro explained, “By producing the sheaths in-house, we maintain greater control over quality and supply; and we can provide our customers with the solutions they need faster.”

Manufacturing operations will remain at the Tempe, AZ facility. Headquartered in Buffalo, NY, Conax Technologies is a designer and manufacturer of standard and custom engineered temperature sensors, compression seal fittings and feedthroughs, probes, sensors, wires, electrodes and fiber optic cables. The company has locations on the US west coast, as well as in Canada, Europe and Asia.

Avantor Performance Materials, LLC, announced today the acquisition of Puritan Products, Inc., a supplier of cGMP buffers and solutions for Biopharma customers, and high-purity chemistries for Research and Electronic Materials customers.

Avantor is a global supplier of ultra-high-purity materials for the life sciences and advanced technology markets. The company provides performance materials and solutions for the production and research needs of approximately 7,900 customers across the biotechnology, pharmaceutical, medical device, diagnostics, aerospace & defense, and semiconductor industries.

“The addition of Puritan is a key next step in our growth plans, as it provides access to new customers in the U.S. and Europe, a broader portfolio of high-purity products for the Biopharma, Research and Electronic Materials industries, and access to additional capabilities, including new cGMP operations and talented new colleagues,” said Michael Stubblefield, CEO of Avantor. “The addition of Puritan’s operations, equipment and sourcing of raw materials offer our customers an additional layer of supply chain security, a key element of the Avantor value proposition.”

Avantor will begin the process of integrating Puritan into the company immediately. Customers will now have access to the J.T.Baker, Macron Fine Chemicals and Puritan brands of high-purity products, as well as Avantor’s other portfolio of brands, including NuSil brand high-purity biomaterials and silicone.

“The Puritan business complements Avantor’s platform very well, particularly the focus on quality manufacturing and regulatory compliance – two areas that are critical in the life science industry,” continued Stubblefield.

ClassOne Technology (classone.com), manufacturer of budget-friendly Solstice plating systems, announced it’s new CopperMax chamber — a design that is demonstrating major copper plating cost reductions for users of ≤200mm wafers.

ClassOne cited actual performance data from a CopperMax pilot installation on a Solstice tool at a Fortune 100 customer. Over a six-month period the customer tracked their actual production operating costs while using the new chamber for copper TSV, Damascene and high-rate copper plating. For the three processes with CopperMax they reported that operating costs were reduced between 95.8% and 98.4% compared with previously used conventional plating chambers.

“Many of our emerging market customers are starting to do copper plating,” said Kevin Witt, President of ClassOne Technology. “So we’ve spent a lot of time on the process, working to reduce customer costs and also increase performance. And the new CopperMax chamber is proving to do both.”

ClassOne pointed out that consumables are the largest cost factor in copper plating. Optimizing copper plating generally requires the use of expensive organic additives — which are consumed very rapidly and need to be replenished frequently.

CopperMax chamber

“We learned, however, that over 97% of those expensive additives were not being consumed by the actual plating process,” said Witt. “Most were being used up simply by contact with the anode throughout the process! So, we designed our new copper chamber specifically to keep additives away from the anode — and the results are pretty dramatic. Significant savings can be realized by high- and medium-volume users with high throughputs as well as by lower-volume and R&D users that have long idle times.”

The company explained that the CopperMax chamber employs a cation-exchange semipermeable membrane to divide the copper bath into two sections. The upper section contains all of the additives, and it actively plates the wafer. The lower section of the bath contains the anode that supplies elemental copper — which is able to travel through the membrane and into the upper section to ultimately plate the wafer. However, the membrane prevents additives from traveling down to the anode, where they would break down and form process-damaging waste products.

As a result, the CopperMax bath remains much cleaner, and bath life is extended by over 20x. This increases uptime, enables higher-quality, higher-rate Cu plating, and it reduces cost of ownership very substantially.

For example, a customer using a Solstice system with six CopperMax chambers and running TSV and high-rate copper plating will save over $300,000 per year just from additive use reductions.

In addition, the CopperMax also reduces Cu anode expenses. The chamber is designed to use inexpensive bulk anode pellets instead of solid machined Cu material, which cuts anode costs by over 50%. And since the pellets have 10x greater surface area they also increase the allowable plating rates.

“Like the rest of our equipment, this new chamber aims to serve all those smaller wafer users who have limited budgets,” said Witt. “Simply stated, CopperMax is going to give them a lot more copper plating performance for a lot less.”

Solstice plating system

Brewer Science announced the achievement of Zero Waste to Landfill Certification for the second consecutive year. GreenCircle Certified, LLC (GreenCircle), has completed extensive audits to verify that the Rolla and Vichy Brewer Science manufacturing locations contribute zero waste to landfills. The certification is valid through 2017 and can be viewed in GreenCircle’s Certified Product Database.

Brewer Science is regarded as a champion for environmental responsibility in the microelectronics and semiconductor industry and is the only business in the industry to achieve Zero Waste to Landfill Certification through GreenCircle. Brewer Science remains committed to a robust environmental management system with the objective of preventing pollution of the environment and providing a healthy, safe, and secure workplace.

For many years Brewer Science leadership has made it a priority to lead an environmentally responsible organization. Some of the initiatives include:

  • In 2002, Brewer Science instituted a mini-bin recycling program, a simple step that had a huge impact. To date, over 597 tons of waste have been recycled.
  • At its headquarters in Rolla, Missouri, Brewer Science promotes a community collection program. Through partnering with waste disposal companies and volunteer crews, they have collected more than 800,000 pounds of appliances, electronics, and tires that would have otherwise been a part of a landfill.
  • In 2015, a giant trash compactor known as “Big Blue” found a home in Brewer Science’s Rolla facility. Big Blue collects and compacts tons of non-recyclable waste and sends it to a waste-to-energy facility. The waste is combusted to produce enough electricity to power four houses for a month.
  • Brewer Science also diverts some of its waste into fuel blending processes, resulting in the conversion of over 520,000 pounds of waste into fuel that can replace natural gas and coal.

As GaN Systems’ gallium nitride transistors revolutionize the power electronics market, the company’s funding partners are being recognized for their investment success. After releasing its 8th annual Global Cleantech 100 list, Cleantech Group (CTG) has awarded GaN Systems investor, Crysalix Venture Capital, the 2017 Financial Investor of the Year Award. The Global Cleantech 100 is a peer-reviewed list of the top private companies involved in innovative clean technology, and that have the greatest potential to impact the future of a wide range of industries within a 5-10 year timeframe. In a parallel development, in its 2016 “Year in Review” report, the CVCA (Canadian Venture Capital and Private Equity Association) reported that GaN Systems’ funding partner, Cycle Capital Management, was recognized for being the most active cleantech venture capital firm in Canada in 2016. Additionally, Cycle Capital was Canada’s 2nd most active independent private venture capital firm, consummating 29 deals and investing at total investment of $132M. According to the CVCA report, Canadian cleantech investments for 2016 experienced a 200% increase over the previous year.

Chrysalix Venture Capital was selected from a field of over 11,000 peer-reviewed nominees. They were chosen for having the highest percentage – in excess of 60% – of their qualifying portfolio companies on the 2017 Global Cleantech 100 list. Chrysalix Venture Capital is a technology-focused investment firm that invests in companies that bring disruptive innovation to the world’s largest industries. GaN Systems, a developer of gallium nitride power switching semiconductors, is one of seven such companies in the investment firm’s portfolio that are also included in the Global Cleantech 100 list.

As stated by Chrysalix President and CEO, Wal van Lierop, “We are honored to be recognized as the Financial Investor of the Year at this year’s Global Cleantech 100. This award is a great endorsement of our portfolio and validation of Chrysalix’s strategy of targeting breakthrough industrial innovations leveraging intelligent systems and components, which we pioneered in our last fund and have made the central focus of our new Chrysalix RoboValley Fund.”

Cycle Capital invests in cleantech entrepreneurial companies that are dedicated to fostering a sustainable future and that produce more with less. Commenting on how GaN Systems fits into its portfolio, Cycle Capital’s Founder and Managing Partner Andrée-Lise Méthot said, “We’re happy to share these results with our portfolio companies because it’s by investing in globally competitive companies led by great entrepreneurial teams like GaN Systems that we become the leader of the cleantech investment in Canada.”

“GaN Systems is proud to be a member of Chrysalix Venture Capital’s portfolio of leading-edge technology companies,” remarked GaN Systems CEO, Jim Witham. “We congratulate our funding partner on being recognized for their forward-thinking, and for winning this well-deserved and highly prestigious award.” Mr. Witham went on to congratulate Cycle Capital, “We’re extremely proud to be a member of the Cycle Capital portfolio of companies who are at the vanguard of the cleantech revolution. By investing in GaN Systems, together we are helping to reduce the world’s exploding demand for more energy, while simultaneously enabling our customers with solutions that give them a competitive advantage.”

The first fully functional microprocessor logic devices based on few-atom-thick layered materials have been demonstrated by researchers from the Graphene Flagship, working at TU Vienna in Austria. The processor chip consists of 115 integrated transistors and is a first step toward ultra-thin, flexible logic devices. Using transistors made from layers of molybdenum disulphide (MoS2), the microprocessors are capable of 1-bit logic operations and the design is scalable to multi-bit operations.

With the drive towards smart objects and the Internet of Things, the microprocessors hold promise for integrating computational power into everyday objects and surfaces. The research is published this week in Nature Communications.

The Graphene Flagship is developing novel technologies based on graphene and related materials (GRMs) such as transition metal dichalcogenides (TMDs) like MoS2, semiconductor materials that can be separated into ultra-thin sheets just a few atoms thick. GRMs are promising for compact and flexible electronic devices due to their thinness and excellent electrical properties.

The ultra-thin MoS2 transistors are inherently flexible and compact, so this result could be directly translated into microprocessors for fully flexible electronic devices, for example, wearable phones or computers, or for wider use in the Internet of Things. The MoS2 transistors are highly responsive, and could enable low-powered computers to be integrated into everyday objects without adding bulk. “In principle, it’s an advantage to have a thin material for a transistor. The thinner the material, the better the electrostatic control of the transistor channel, and the smaller the power consumption,” said Thomas Mueller (TU Vienna), who led the work.

Mueller added “In general, being a flexible material there are new opportunities for novel applications. One could combine these processor circuits with light emitters that could also be made with MoS2 to make flexible displays and e-paper, or integrate them for logic circuits in smart sensors. Our goal is to realise significantly larger circuits that can do much more in terms of useful operations. We want to make a full 8-bit design – or even more bits – on a single chip with smaller feature sizes.”

Talking about increasing the computing power, Stefan Wachter (TU Vienna), first author of the work, said “Adding additional bits of course makes everything much more complicated. For example, adding just one bit will roughly double the complexity of the circuit.”

Compared to modern processors, which can have billions of transistors in a single chip, the 115-transistor devices are very simple. However, it is a very early stage for a new technology, and the team have concrete plans for the next steps: “Our approach is to improve the processing to a point where we can reliably make chips with a few tens of thousands of transistors. For example, growing directly onto the chip would avoid the transfer process, which would give higher yield so that we can go to more complex circuits,” said Dmitry Polyushkin (TU Vienna), an author of the work.

Graphene Flagship researchers from AMBER at Trinity College Dublin have fabricated printed transistors consisting entirely of layered materials. Published today in the leading journal Science, the team’s findings have the potential to cheaply print a range of electronic devices from solar cells to LEDs with applications from interactive smart food and drug labels to next-generation banknote security and e-passports.

Led by Professor Jonathan Coleman from AMBER (the Science Foundation Ireland-funded materials science research centre hosted in Trinity College Dublin), in collaboration with the groups of Professor Georg Duesberg (AMBER) and Professor Laurens Siebbeles (TU Delft, Netherlands), the team used standard printing techniques to combine graphene flakes as the electrodes with other layered materials, tungsten diselenide and boron nitride as the channel and separator (two important parts of a transistor) to form an all-printed, all-layered materials, working transistor.

All of these are flakes are a few nanometres thick but hundreds of nanometres wide. Critically, it is the ability of flakes made from different layered materials to have electronic properties that can be conducting (in the case of graphene), insulating (boron nitride) or semiconducting (tungsten diselenide) that enable them to create the building blocks of electronics. While the performance of these printed layered devices cannot yet compare with advanced transistors, the team believe there is a wide scope to improve the performance of their printed TFTs beyond the current state-of-the-art.

Professor Coleman, who is an investigator in AMBER and Trinity’s School of Physics, said, “In the future, printed devices will be incorporated into even the most mundane objects such as labels, posters and packaging. Printed electronic circuitry will allow consumer products to gather, process, display and transmit information: for example, milk cartons will send messages to your phone warning that the milk is about to go out-of-date. We believe that layered materials can compete with the materials currently used for printed electronics.”

All of the layered materials were printed from inks created using the liquid exfoliation method previously developed by Professor Coleman and already licensed. Using liquid processing techniques to create the layered materials inks is especially advantageous in that it yields large quantities of high quality layered materials which helps to enable the potential to print circuitry at low cost.

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.’

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.”