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Posts Tagged ‘thin films’

NFC IGZO TFT for Game Cards

Thursday, November 20th, 2014

By Ed Korczynski, Senior Technical Editor, SemiMD

Thin-film transistors (TFT) made with indium-gallium-zinc-oxide (IGZO) can perform significantly better than TFTs made with low-temperature-poly-silicon (LTPS), and can be made ultra-thin and flexible for integration into a wide variety of devices. Researchers at the Holst Centre—an R&D incubator launched by the Belgian imec and the Dutch TNO in 2005—have been working on flexible TFTs for many years for many applications include flexible displays, intelligent food packaging, and paper identification (ID) documents. Now Holst Center is collaborating with Cartamundi NV, a world leader in production and sales of card and board games, to develop ultra-thin flexible near field communication (NFC) tags for game cards. The goal is an enhanced gaming experience that is interactive and intuitive.

Cartamundi creates specialized game cards such as these, and has been working on cards with embedded silicon NFC chips for many years. (Source: Cartamundi)

Cartamundi has been working on “iCards” that provide a connection between the physical products and the digital world for many years, and has recently claimed traction with games for the “connected generation”. By working with the Holst Centre to create IGZO TFTs on plastic, Cartamundi aims to lower overall costs while also creating both a thinner and a more robust NFC chip. Currently, Cartamundi NV embeds silicon-based NFC chips in their game cards, connecting traditional game play with electronic devices such as smartphones and tablets. The advanced IGZO TFT technology should improve and broaden the applicability of interactive technology for game cards, compared to the currently-used silicon based NFC chips.

Chris Van Doorslaer, chief executive officer of Cartamundi, said, “Cartamundi is committed to creating products that connect families and friends of every generation to enhance the valuable quality time they share during the day. With Holst Centre’s and imec’s thin-film and nano-electronics expertise, we’re connecting the physical with the digital which will enable lightweight smart devices with additional value and content for consumers.”

“Not only will Cartamundi be working on the NFC chip of the future, but it will also reinvent the industry’s standards in assembly process and the conversion into game cards,” says Steven Nietvelt, chief innovation and marketing officer at Cartamundi. “All of this is part of an ongoing process of technological innovation inside Cartamundi. I am glad our innovation engineers will collaborate with the strongest technological researchers and developers in the field at imec and Holst Centre. We are going to need all expertise on board. Because basically what we are creating is game-changing technology.”

The major challenges are two-fold:  low-temperature formation of the IGZO layer, and integration of the IGZO into a complex NFC circuit on plastic. Control of surface states and defect densities is always essential for the production of any working semiconductor device, and defects act as traps for electrons flowing through circuitry. Consequently, for TFT instead of bulk crystal devices the precise control of the many deposited thin-films is essential.

Holst Centre, imec and Cartamundi engineers will look into NFC circuit design and TFT processing options, and will investigate routes for up-scaling of Holst processes to run on large production presses. By keeping the IGZO TFT manufacturing costs low, the flexible chips are intended to be a critical part of Cartamundi’s larger strategy of developing game cards for the connected generation.

“Imec and Holst Centre aim to shape the future and our collaboration with Cartamundi will do so for the future of gaming technology and connected devices,” says Paul Heremans, Department Director Thin Film Electronics at imec and Technology Director at the Holst Centre. “Chip technology has penetrated society’s daily life right down to game cards. We are excited to work with Cartamundi to improve the personal experience that gaming delivers.”

While game cards may not seem as important as healthcare and communications, flexible NFC integration into cards could generate IGZO TFT production volumes that are game changing.

—E.K.

Research Alert: Dec. 10, 2013

Tuesday, December 10th, 2013

Research team finds way to make solar cells thin, efficient and flexible

Converting sunshine into electricity is not difficult, but doing so efficiently and on a large scale is one of the reasons why people still rely on the electric grid and not a national solar cell network.

But a team of researchers from the University of Illinois at Urbana-Champaign and the University of Central Florida in Orlando may be one step closer to tapping into the full potential of solar cells. The team found a way to create large sheets of nanotextured, silicon micro-cell arrays that hold the promise of making solar cells lightweight, more efficient, bendable and easy to mass produce.

The team used a light-trapping scheme based on a nanoimprinting technique where a polymeric stamp mechanically emboss the nano-scale pattern on to the solar cell without involving further complex lithographic steps. This approach has led to the flexibility researchers have been searching for, making the design ideal for mass manufacturing, said UCF assistant professor Debashis Chanda, lead researcher of the study.

Polymers can be semimetals

Traditional plastics, or polymers, are electrical insulators. In the seventies a new class of polymers that conduct electricity like semiconductors and metals was discovered by Alan J.Heeger, Alan G. MacDiarmid and Hideki Shirakawa. This was the motivation for their Nobel Prize in Chemistry year 2000. Now Xavier Crispin, Docent in organic electronics at Linköping University’s Department of Science and Technology, has led a project where no fewer than twenty researchers from five universities worldwide have collaborated to prove that polymers can also be semimetals.

Xavier Crispin discovered that conductive polymers can be thermoelectric. A thermoelectric material undergoes a diffusion of electronic charge carriers to the cold region when the material is submitted to a temperature gradient. As a result an electric potential is created between the cold and hot side of the material. This thermo-voltage is the basis of thermo-couples used for instance in an everyday oven thermometer.

The theoretical input of Igor Zozoulenko, advanced spectroscopic analysis by Mats Fahlman and Weimin Chen at Linköping University, as well as state-of-the-art polymer samples and morphology studies by research colleagues in Australia, Belgium, Norway and Denmark showed the exact same thing: the polymer, in this case a doped variant of the plastic PEDOT, behaves exactly like a semimetal, which also explains the high Seebeck effect.

Pioneering path to electrical conductivity in ‘tinker toy’ materials

Sandia National Laboratories researchers have devised a novel way to realize electrical conductivity in metal-organic framework (MOF) materials, a development that could have profound implications for the future of electronics, sensors, energy conversion and energy storage.

A paper to appear in Science magazine, “Tunable Electrical Conductivity in Metal-Organic Framework Thin-Film Devices,” debuts in the Dec. 5 edition of Science Express. The paper — co-authored by a group of Sandia researchers and collaborators at the National Institute of Standards and Technology (NIST) — describes a technique that experiments show successfully increases the electrical conductivity of one MOF by over six orders of magnitude.

“Fundamentally, this sheds enormous light on the conduction process in these materials,” said Alec Talin, a material scientist at Sandia and the paper’s lead author.

Applications for electrically conducting MOFs, said Sandia senior scientist Mark Allendorf, include chemical sensing, medical diagnostics, energy harvesting and storage and microelectronics.

Solid State Watch: Nov. 15-22, 2013

Friday, November 22nd, 2013
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Research Bits: Oct. 22, 2013

Tuesday, October 22nd, 2013

Size matters in the giant magnetoresistance effect in semiconductors

Professors at Georgia State University reported that a giant magnetoresistance effect depends on the physical size of the device in the GaAs/AlGaAs semiconductor system.

In research that is supported by grants from the U.S. Department of Energy and the U.S. Army Research Office, Dr. Ramesh Mani, professor of physics and astronomy, studied the magnetoresistance in flat, very thin sheets of electrons in the ultra high quality GaAs/AlGaAs semiconductor with his colleagues Annika Kriisa from Emory University and Werner Wegscheider from the ETH-Zurich in Switzerland.

The researchers found that the change in the resistance or resistivity with the magnetic field depends on the size of the device. They demonstrated that, under the application of a magnetic field, wide devices develop a smaller and quicker change, while small devices develop a bigger but slower change in the resistivity. The resistance or resistivity of a material to the flow of electricity is a technologically important property, especially in semiconductors.

This research team developed a model to understand the observations and deduced that when the semiconductor system becomes of even better quality, the change in the resistance under the application of a magnetic field will become even bigger. Indeed, the change might become so big that the resistance vanishes entirely in the small magnetic field.

Thin film semiconductors that will drive production of next-generation displays

Researchers at the National Institute for Materials Science have developed a pixel switching semiconductor, which will be the key to driving next-generation displays, by using an oxide film with a new elemental composition.

When an oxide film contains metal with low bond dissociation energy, the thin film absorbs or desorbs oxygen easily and the conductivity of the film changes. For example, zinc has very low bond dissociation energy, so a thin film using zinc absorbs or desorbs oxygen easily when heated or cooled. This finding suggests that the manufacturing conditions for oxide semiconductors can be controlled by focusing on the bond dissociation energy. In fact, the research team confirmed that film deposition conditions can be broadened by adding silicon oxide with high bond dissociation energy to indium oxide. We also confirmed stabilization of thin-film conductivity in post-deposition heat treatment.

The research results are expected to be effective not only for reducing the power consumption of displays which consume about half of the power in rapidly diffusing smartphones, but also for achieving higher frequencies to realize higher-definition TVs. Additionally, the thin film developed in this research contributes to conserving precious resources by not using zinc, which is a trace element of concern, or high-cost gallium which is used in large quantities for galvanized steel sheets or as a rubber vulcanizing agent, while it also enables the manufacture of flat panel displays not affected by wild fluctuations in raw material prices.

Ultraviolet light to the extreme

When you heat a tiny droplet of liquid tin with a laser, plasma forms on the surface of the droplet and produces extreme ultraviolet (EUV) light, which has a higher frequency and greater energy than normal ultraviolet.Now, for the first time, researchers have mapped this EUV emission and developed a theoretical model that explains how the emission depends on the three-dimensional shape of the plasma. In doing so, they found a previously untapped source of EUV light, which could be useful for various applications including semiconductor lithography, the process used to make integrated circuits.

In the experiments, Andrea Giovannini and Reza Abhari from ETH-Zurich in Switzerland blasted a 30-micron-diameter droplet of tin with a high-powered laser 6,000 times a second. They measured the spatial distribution of the resulting EUV emission and found that 30 percent of it came from behind the region of the droplet that was struck by the laser. According to their model, this unexpected distribution was due to the fact that the plasma partially surrounding the droplet was elongated in the direction of the laser pulse.

Devices that produce narrow beams of EUV for purposes like in semiconductor lithography use mirrors to focus the emission. But, until now, no one knew to collect the EUV light radiating from behind the droplet.


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