Concept and image of the junction (via The Imperial College London)

The common touch panel interfaces have a delay in response time, and it doesn't get better over time as the system gets burdened with software. The Imperial College London (ILC) and the King Abdullah University of Science and Technology (KAUST) are teaming up to solve this issue. They have come up with a new organic composite material made of a blend of two organic semiconductors to make up organic thin film transistors (OTFTs).

These scientists, along with the Center For Plastic Electronics, have combined the distinct useful qualities of polymer semiconductors with soluble small-molecule semiconductors to create a thin film. Small-molecule semiconductors are very effective, but they are difficult to manufacture into a thin film. Contrary, polymer semiconductors make thin films easily, but they do not have high charge carrier capabilities. The team found that creating a composite material with both materials resulted in a thin film with a charge carrier mobility that exceeds 5 cm²/V*s, which similar to the high mobility of a single crystal made of small-molecules semiconductors.

This film has a crystalline texture due to the small-molecule component and a remarkable flatness and smoothness atop the polycrystalline film. Both of these factors improve the performance of the materials response time and are crucial in top-gate, bottom-contact configuration devices.

Using methods like x-ray scattering, cross-sectional energy-filtered transmission electron microscopy and atomic force microscopy in topographic and phase modes, researchers may be able to obtain OTFTs with higher mobilities.  Speaking about the future of OTFTs, Dr. Anthopoulos from the Imperial team said, "In principle, this simple blend approach could lead to the development of organic transistors with performing characteristics well beyond the current state-of-the-art."

Microsoft demonstrates the benefits of a faster response time in their "Path for the next 10 years" announcement. Follow the link to see more.

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Graphene sheet concept art from James Hedberg

Why has Graphene not over taken Silicon for use in electronics?

Graphene is a single layer of carbon atoms that are only one molecule thick and have extraordinary characteristics. It is stronger than diamonds, can conduct electricity better than copper, and is impenetrable to gases and liquids. The low resistance it offers can create new and better transistors and circuits. The exceptional conductivity allows electrons to flow quicker than the modernly used silicon transistors.

However, with the incredible speed also comes another problem. For transistors to work they have to have a distinct on and off state. Creating a transistor with a consistent off state is difficult due to the great conductivity of the substance. Even with sheets as thin as one molecule electrons often filter through when  in the off state. The band-gap cannot get large enough to be effective.

One man, Konstantin Novoselov, leading a group of researchers is working to create an efficient graphene based transistor. His work on Graphene in 2010 helped him, with colleague Andre Geim, win the Nobel Prize in Physics. Currently they are working to develop a transistor by placing a layer of molybdenum in between two sheets of graphene. The molybdenum is an excellent insulator and stops electrons from passing over while the transistor is in the off state. Further research and experimentation is still needed. Successfully creating a graphene transistor could significantly expand our capabilities with hardware engineering.

Take the 155Ghz Graphene transistor as an example of the possibilities.

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A baseball covered in the DOE Berkely stretchable thin film transistor array material (via DOE Berkely)

Many researchers are part of a race to creating stretchable/bendable electronics. Seamlessly integrated wearable electronics is now an inevitability. The U.S. Department of Energy (DOE) is no slouch in this area either with their latest development, large-area  carbon-nanotube thin film transistor networks.

The material was developed at the Lawrence Berkely National Laboratory. The high charge mobility outstrips the capabilities of its organic counterparts. The team's first application was to take transistor network, they dubbed "e-skin," and use it as a touch interface.

A major issue the team tackled in this project was the carbon nanotube's low band-gap ratio (the on/off ratio, as the team called it). To defeat the low on/off ratio of the material the team had to make the purest solution of single-wall carbon nanotubes (SWNT) as possible. They make a solution that was 99% semiconductor SWNT. Applying this solution to a polymide substrate created the base material. To make it flexible, a hexagonal (honeycomb) shape was laser-cut into the sheets at a pitch of 3.3mm and a hole-side lenth between 1 - 1.85mm. 

The paper's co-author Toshitake Takahashi explained the purpose on the holes, "The degree to which the substrate could be stretched increased from 0 to 60-percent as the side length of the hexagonal holes increased to 1.85 mm... In the future, the degrees of stretchability and directionality should be tunable by either changing the hole size or optimizing the mesh design.”

The final prototype was a 24 square centimeter "sensor pixel" array. The image below shows the pressure indication map of an "L" shaped object on top of the material. Max pressure of 15 kilo Pascals was sensed.

(via DOE Berkely)

Takahashi stated that using this array could make for a good touch input backplane for flexible displays in the near future. A common mantra spoken by many in the industry.

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More projects in the flextronics industry:

Transparent graphene transistor material stretches beyond all others
Molybdenite to replace silicon, and the 3-atom thick transistor
Cotton transistor and wearable electronics
Flexible memory breaks through flex limitations
Coiled nanowires could help with stretchable electronics
Stretchable silicon to make ‘smarter’ sports apparel

Molybdenite transistor (left) Molybdenite IC with multiple transistors (right) (Via EPFL)

Will element14 have to change its name to element42+(2)16?

Researchers at École Polytechnique Fédérale de Lausanne (EPFL) has shown that Molybdenite's (MoS2)  miniaturization electrical properties outstrip silicon and rivals graphene. The team stated that they are able to make a transistor that is only 3-atoms thick. Silicon at that scale has the tendency to develop surface oxidization, destroying its electrical properties. (The smallest silicon transistor is 2nm thick.)

EPFL Laboratory of Nanoscale Electronics and Structures (LANES) director Andras Kis explained the latest development, "We have built an initial prototype, putting from two to six serial transistors in place, and shown that basic binary logic operations were possible, which proves that we can make a larger chip." This comes off the cusp of creating one MoS2 transistor back in February, 2011.

Molybdenite transistor render with amplify graph (via EPFL and ACS NANO)

Kis stated about the further property advantages, "They can be turned on and off much more quickly, and can be put into a more complete standby mode." MoS2 is an efficient material, that also has the ability to amplify electrical signals exactly like silicon. A 4x amplification is possible with incoming signals. Kis again, "With graphene, for example, this amplitude is about 1. Below this threshold, the output voltage would not be sufficient to feed a second, similar chip."

MoS2 is flexible to the point of folding, use in Flextronics in unavoidable. Electron mobility of MoS2 is up to 800 cm2/Vs. Which is only slightly less than that of silicon, but by far less than the 120,000 cm2/Vs of graphene. However, MoS2 has a bandgap great enough for switching operations at 1.8 eV, unlike graphene's 0.25 eV. Which means MoS2 based transistors can turn off more completely than graphene.

MoS2 is a naturally-occurring mineral that is quite abundant. The demand for smaller electronics will eventually push companies to use Molybdenite. It is only a matter of time.

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Analog IC that mimics a single synapse (via Guy Rachmuth and MIT)

Modeling the human brain into a usable computer is the basis for much research to date. IBM is attempting to build a computer system that rivals the human mind through brute force, one for one, copying the 100 billion neurons and 100 trillion synapses. Statistically so, the computer will be similar, but could it learn like a brain?

MIT and Harvard have modeled a new IC to follow how the brain learns. In the team's chip, 400 transistors simulate a single synapse. This acts as a digital representation of the pathway that nerve impulses from an axon travels before reaching neurons. More specifically, the chip emulates the ion channels. Neurons change their cell characteristics by releasing neurotransmitters (glutamate or GABA) which bind the receptors of postsynaptic cell membranes. This opens or closes the ion channels, which changes the cell's electrical potential.

The team was most concerned with two features of the synaptic connections, long-term depression (LTD) and long-term potentiation (LTP). LTD reduces the synaptic efficiency for periods of time, while LTP enhances. These processes are controlled by the flow of charged atoms (ie: sodium, calcium, potassium) through ion channels. The MIT chip mimics these processes closely in an analog fashion.

MIT-Harvard Division of Health Sciences and Technology explained their achievement further, "We now have a way to capture each and every ionic process that’s going on in a neuron. [The IC is a] significant advance in the efforts to incorporate what we know about the biology of neurons and synaptic plasticity onto CMOS [complementary metal-oxide-semiconductor] chips. If you really want to mimic brain function realistically, you have to do more than just spiking. You have to capture the intracellular processes that are ion channel-based. We can tweak the parameters of the circuit to match specific ion channels."

Aside from using this technology study brain function from a different perspective, build communication networks between the brain and artificial prosthetics, or step closer to a true artificial intelligence. If this team could only partner with IBM's SyNAPSE program, and they could both catalyst their way to another level.

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Other emulated mind news:

The human brain computer from IBM

Electronic brain via nanotubes

Final  graphene material (left). Magnified transistor image (center).  Transistors placed onto a balloon. (right) (Via Lee, American Chemical  Society)

There appears to be legions of engineers and scientists pushing hard for stretchable electronics.  The latest comes in the form of a transparent material containing sets  of graphene transistors. Up to a 5% flex could be achieved before  degradation of the electrical qualities.

In an effort that spans 10 schools, project lead Jeong Ho Cho from Soongsil University and Jong-Hyun Ahn from Sungkyunkwan University,  both are South Korea, found a way to overcome common issues with making  transparent and flexible electronics by using a different type of  substrate. In past attempts, a slab of rubber or balloon surface was  used with limited flexibility. Jeong and his team fabricated single  layers of graphene onto copper foil. Using photolithography and etching  tricks, the transistor components (electrodes, semiconducting channels)  were forced into the graphene layers. The etched graphene was  transferred to the clear rubber. A stretchable ion-gel was used in the  final step to finish the transistor's components, gate insulators and  electrodes.

Graphene  can  be printed at low, and even at room, temperatures. This gave the  team an easy way to make and manipulate the organic graphene. At the  same time, graphene's innate stretch ability was ultimately the key to  their success. The fabricated material could bend at a maximum of 5% for  1,000 flexes. After which micro-cracks started forming dues to  imperfections in the graphene layers.

As  most researchers will say, the team vows to improve the capabilities of  their transparent flex transistors. The team sees applications in  medical biosensores that form to the human body and flex  displays. 100%  flexibility is what they need, but that final 95% is always the  hardest.

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Although  the researchers are using graphene transistors, the actual operation of  which may be in question. The band-gap ratio for graphene is around 30.  The larger the band gap, the more of an insulator the material becomes.  For comparison, the band gap of silicon is 1.11.

Single molecule electronics is the ultimate goal in shrinking electrical circuits. Where a single molecules or groups of molecules are used as traditional electrical components. Some researchers at the orbital fringe of nanotechnology have designed, built, single molecule transistors. For example, physicists at the University of Arizona working with Chemists at the University of Madrid built a ring-shaped molecule of benzene that functions like a transistor. They dubbed it the "QuIET," Quantum Interference Effect Transistor, and promptly applied for a patent.

UA ring-shaped transistor. Gold colored moledules are metalic contacts.

UA is not alone. Single molecule transistors have also been made by the following:

1. Harvard University, Hongkun Park made a molecule of 2 atoms of vanadium between gold electrodes

2. Dr Robert Wolkow, at Canada's National Institute for Nanotechnology made one from styrene

3. Yale & Gwangju Institute in Korea controlled energy passing through a molecule by manipulation voltage levels

4. University of Liverpool, Dr Werner Hofer, showed a single atom can control conductivity of a nearby molecule

All of these people have the same issue, how to connect wires to their transistors. Various methods have been attempted in the past, but with little or no success. Yuji Okawa from the National Institute for Materials Science, Japan, has the latest and more potential solution to the problem. With a monomolecular film of diacetylene on a graphite substrate, a deposit of phthalocyanine is applied to form nanoclusters. A pulsed voltage is applied from the tip of a scanning tunneling microscope across that deposit. The result is a sequential polymerization of the diacetylene that binds with the phthalocyanine layer . In other words, a polymer nanowire is drawn to connect to each single molecule electrical component.

Depiction of the scanning tunneling microscope placing a wire.

Okawa and his team will attempt to make a single circuit based on his research and development. Molecular electronics are closer than ever. Now, which one of the transistor makers above will be the first to adopt Okawa's wires?

Eavesdropper

Intel has moved from planar transistors to, 3D, tri-gate transistors. This allows for the increase of speed, reduced power consumption (50% at constant, 37% in low voltage conditions), and of course performance and efficiency. Intel found that shrinking to 22nm did not meet Moore's Law expectations, but changing the individual transistor functions was the only way to meet the goal. Estimates bring the manufacturing costs of the tri-gate to 2-3% over current silicon-wafer construction. The 3D transistor processor, codenamed Ivy Bridge, will go into production and distribution in the second half of 2011. 14nm and 10nm chips with 3D transistors are being planned for 2015. Intel states that this tech is not limited to the cutting edge, so we will see wide adoption of the technique across Intel's product families.

I included the above video for  Mark T. Bohr's deadpan performance. He made the corny jokes in the video, acceptable. Like the tri-gate transistor, that is a commendable achievement in itself.

Eavesdropper