Smart Printed Electronics

Researchers in AMBER, the materials science research centre hosted in Trinity College Dublin, have fabricated printed transistors consisting entirely of 2-dimensional nanomaterials for the first time. These 2D materials combine exciting electronic properties with the potential for low-cost production. This breakthrough could unlock the potential for applications such as food packaging that displays a digital countdown to warn you of spoiling, wine labels that alert you when your white wine is at its optimum temperature, or even a window pane that shows the day’s forecast

This discovery opens the path for industry, such as ICT and pharmaceutical, to cheaply print a host 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.

printed transistor

Prof Jonathan 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 (constructed from the devices we have created) will allow consumer products to gather, process, display and transmit information: for example, milk cartons could send messages to your phone warning that the milk is about to go out-of-date.

We believe that 2D nanomaterials can compete with the materials currently used for printed electronics. Compared to other materials employed in this field, our 2D nanomaterials have the capability to yield more cost effective and higher performance printed devices. However, while the last decade has underlined the potential of 2D materials for a range of electronic applications, only the first steps have been taken to demonstrate their worth in printed electronics. This publication is important because it shows that conducting, semiconducting and insulating 2D nanomaterials can be combined together in complex devices. We felt that it was critically important to focus on printing transistors as they are the electric switches at the heart of modern computing. We believe this work opens the way to print a whole host of devices solely from 2D nanosheets.”
Led by Prof Coleman, in collaboration with the groups of Prof Georg Duesberg (AMBER) and Prof. Laurens Siebbeles (TU Delft, Netherlands), the team used standard printing techniques to combine graphene nanosheets as the electrodes with two other nanomaterials, tungsten diselenide and boron nitride as the channel and separator (two important parts of a transistor) to form an all-printed, all-nanosheet, working transistor.

The AMBER team’s findings have been published today in the journal Science*.


Carbon Nanotubes Self-Assemble Into Tiny Transistors

Carbon nanotubes can be used to make very small electronic devices, but they are difficult to handle. University of Groningen (Netherlands) 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 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.

polymer wrapped nanotube

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.’

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.

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.’

The results were published in the journal Advanced Materials on 5 April.

Nanocomputer Confirms The Moore’s Law

A research team led by faculty scientist Ali Javey at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has done just that by creating a transistor with a working 1-nanometer gate. For comparison, a strand of human hair is about 50,000 nanometers thick. The development could be key to keeping alive Intel co-founder Gordon Moore’s prediction that the density of transistors on integrated circuits would double every two years, enabling the increased performance of our laptops, mobile phones, televisions, and other electronics. For more than a decade, engineers have been eyeing the finish line in the race to shrink the size of components in integrated circuits. They knew that the laws of physics had set a 5-nanometer threshold on the size of transistor gates among conventional semiconductors, about one-quarter the size of high-end 20-nanometer-gate transistors now on the market.


We made the smallest transistor reported to date,” said Javey, lead principal investigator of the Electronic Materials program in Berkeley Lab’s Materials Science Division. “The gate length is considered a defining dimension of the transistor. We demonstrated a 1-nanometer-gate transistor, showing that with the choice of proper materials, there is a lot more room to shrink our electronics.” The key was to use carbon nanotubes and molybdenum disulfide (MoS2), an engine lubricant commonly sold in auto parts shops. MoS2 is part of a family of materials with immense potential for applications in LEDs, lasers, nanoscale transistors, solar cells, and more.

The findings were published in the journal Science.


Electronics Enter The Nanocomputer Age

An UAlberta research team is developing atom-scale, ultra-low-power computing devices to replace transistor circuits. In the drive to get small, Robert Wolkow and his lab at the University of Alberta are taking giant steps forward. The digital age has resulted in a succession of smaller, cleaner and less power-hungry technologies since the days the personal computer fit atop a desk, replacing mainframe models that once filled entire rooms. Desktop PCs have since given way to smaller and smaller laptops, smartphones and devices that most of us carry around in our pockets. But as Wolkow points out, this technological shrinkage can only go so far when using traditional transistor-based integrated circuits. That’s why he and his research team are aiming to build entirely new technologies at the atomic scale.
Our ultimate goal is to make ultra-low-power electronics because that’s what is most demanded by the world right now,” said Wolkow, the iCORE Chair in Nanoscale Information and Communications Technology in the Faculty of Science. “We are approaching some fundamental limits that will stop the 30-year-long drive to make things faster, cheaper, better and smaller; this will come to an end soon. “An entirely new method of computing will be necessary.”

Wolkow and his team in the U of A’s physics department and the National Institute for Nanotechnology are working to engineer atomically precise technologies that have practical, real-world applications. His lab already made its way into the Guinness Book of World Records for inventing the world’s sharpest object—a microscope tip just one atom wide at its end.


How To Build A Nanocomputer Using Graphene

A team of researchers from the University of California, Riverside’s Bourns College of Engineering, led by Alexander Balandin and Roger Lake, have greatly facilitate the use of graphene in electronic devices. A transistor implemented with graphene will be very fast but will suffer from leakage currents and power dissipation while in the off state because of the absence of the energy band gap. Efforts to induce a band-gap in graphene via quantum confinement or surface functionalization have not resulted in a breakthrough. Now, thanks to the University of California Riverside team findings, graphene applications in electronic circuits for information processing are feasible.

Graphene is a single-atom thick carbon crystal with unique properties beneficial for electronics including extremely high electron mobility and phonon thermal conductivity. However, graphene does not have an energy band gap, which is a specific property of semiconductor materials that separate electrons from holes and allows a transistor implemented with a given material to be completely switched off

Most researchers have tried to change graphene to make it more like conventional semiconductors for applications in logic circuits,” Balandin said. “This usually results in degradation of graphene properties. For example, attempts to induce an energy band gap commonly result in decreasing electron mobility while still not leading to sufficiently large band gap.
We decided to take alternative approach,” Balandin said. “Instead of trying to change graphene, we changed the way the information is processed in the circuits.”


How To Create NanoComputers

Researchers are developing a new type of semiconductor technology for future computers and electronics based on “two-dimensional nanocrystals” layered in sheets less than a nanometer thick that could replace today’s transistors. New technologies will be needed to allow the semiconductor industry to continue advances in computer performance driven by the ability to create ever-smaller transistors.


We are going to reach the fundamental limits of silicon-based CMOS technology very soon, and that means novel materials must be found in order to continue scaling,” said Saptarshi Das, who has completed a doctoral degree, working with Joerg Appenzeller, a professor and scientific director of nanoelectronics at Purdue‘s Birck Nanotechnology Center. “I don’t think silicon can be replaced by a single material, but probably different materials will co-exist in a hybrid technology.


The Smallest Transistor Ever to Be Built

Silicon’s crown is under threat: The semiconductor’s days as the king of microchips for computers and smart devices could be numbered, thanks to the development of the smallest transistor ever to be built from a rival material, indium gallium arsenide.

A cross-section transmission electron micrograph of the fabricated transistor. The central inverted V is the gate. The two molybdenum contacts on either side are the source and drain of the transistor. The channel is the indium gallium arsenide light color layer under the source, drain and gate.

The compound transistor, built by a team in MIT’s Microsystems Technology Laboratories, performs well despite being just 22 nanometers (billionths of a meter) in length. This makes it a promising candidate to eventually replace silicon in computing devices, says co-developer Jesús del Alamo, the Donner Professor of Science in MIT’s Department of Electrical Engineering and Computer Science (EECS), who built the transistor with EECS graduate student Jianqian Lin and Dimitri Antoniadis, the Ray and Maria Stata Professor of Electrical Engineering.

Single-Atom Transistor

Micro-engineering, physicists from the University of South Wales in Australia – UNSW – have created a working transistor consisting of a single atom placed precisely in a silicon crystal. The tiny electronic device, described today in a paper published in the journal Nature Nanotechnology, uses as its active component an individual phosphorus atom patterned between atomic-scale electrodes and electrostatic control gates. This unprecedented atomic accuracy may yield the elementary building block for a future quantum computer ( or nanocomputer) with unparalleled computational efficiencyUntil now, single-atom transistors have been realised only by chance, where researchers either have had to search through many devices or tune multi-atom devices to isolate one that works.

“But this device is perfect”, says Professor Michelle Simmons, group leader and director of the ARC Centre for Quantum Computation and Communication Technology at UNSW. “This is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy.” The microscopic device even has tiny visible markers etched onto its surface so researchers can connect metal contacts and apply a voltage, says research fellow and lead author Dr Martin Fuechsle from UNSW.

Our group has proved that it is really possible to position one phosphorus atom in a silicon environment – exactly as we need it – with near-atomic precision, and at the same time register gates,” he says.