Fresh Electronics News

Graphene is the two-dimensional crystalline form of carbon, whose extraordinary electron mobility and other unique features hold great promise for nanoscale electronics and photonics. But there’s a catch: graphene has no bandgap.

“Having no bandgap greatly limits graphene’s uses in electronics,” says Feng Wang of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, where he is a member of the Materials Sciences Division. “For one thing, you can build field-effect transistors with graphene, but if there’s no bandgap you can’t turn them off! If you could achieve a graphene bandgap, however, you should be able to make very good transistors.”

Wang, who is also an assistant professor in the Department of Physics at the University of California at Berkeley, has achieved just that. He and his colleagues have engineered a bandgap in bilayer graphene that can be precisely controlled from 0 to 250 milli-electron volts (250 meV, or .25 eV).

Using infrared beamline 1.4 at the ALS, under the direction of ALS physicist Michael Martin and Zhao Hao of the Earth Sciences Division, Wang and his colleagues were able to send a tight beam of synchrotron light, focused on the graphene layers, right through the device. As the researchers tuned the electrical fields by precisely varying the voltage of the gate electrodes, they were able to measure variations in the light absorbed by the gated graphene layers. The absorption peak in each spectrum provided a direct measurement of the bandgap at each gate voltage.

“In principle we could have used a tunable laser to measure the optical transmission, but the 1.4 beamline is very bright and can be focused down to the diffraction limit – an important consideration when the graphene-flake target is so small,” Wang says. “Also, compared to a laser, the beamline provides a wider range of frequencies all at once, so we don’t have to painstakingly tune to each absorption frequency we’re trying to measure.”

What these researchers basically did was to create a material that could replace semiconductors one day with a cheap and simple structure, allowing multicolour LEDs to be fabricated. They could be printed on virtually anything, and unleash a whole new set of displaying possibilities.

The price of electronics has been reflecting the work necessary to make them, since they were invented. Silicon-based transistors broke many barriers when they have been invented several decades ago, making the transition from lamps to a whole new universe of possibilities.

Now, scientists are studying technologies that could change even the once all-mighty silicon transistors, by making them from organic materials. Physicists from Umeå University, Sweden, have invented electronic circuits that can be made from a chemical solution. “This makes it possible to paint thin films of electronic materials on flexible surfaces like paper or plastic,” explains Ludvig Edman. Continue reading »

Graphene is a one-layer carbon material, discovered relatively recent, in 2004. It features a lot of interesting properties, and it can be used in power-saving electronic devices, fact that gives it green credits.

MIT researchers discovered another use to graphene. They discovered that it can successfully be used in frequency multiplying applications. Frequency multiplying is the phenomenon that takes place in every cell phone, TV set or radio device. The problems with frequency multiplying until now were the noise that appeared when you got over a certain threshold, and the complexity of the device doing that. Continue reading »

Carbon nanotubes are getting green credits lately, because of their ever new interesting properties. Besides those credits, scientists have discovered other phenomena that could boost wireless communications, also with a green twist.

Researchers from the University of Cincinnati have discovered new uses of spinning carbon nanotubes into longer fibers with additional useful properties. Vesselin Shanov and Mark Schultz created the powerful nanotubes, that are stronger than steel at a much lower density. Continue reading »

The scientists’ research demonstrates a marriage of two emerging fields of research – nanophotonics and nanomechanics, which makes possible the extreme miniaturization of optics and mechanics on a silicon chip.

The energy of light has been harnessed and used in many ways. The “force” of light is different – it is a push or a pull action that causes something to move.

“While the force of light is far too weak for us to feel in everyday life, we have found that it can be harnessed and used at the nanoscale,” said team leader Hong Tang, assistant professor at Yale. “Our work demonstrates the advantage of using nano-objects as “targets” for the force of light — using devices that are a billion-billion times smaller than a space sail, and that match the size of today’s typical transistors.” Continue reading »

They’ve made electronics that can bend. They’ve made electronics that can stretch.

And now, they’ve reached the ultimate goal — electronics that can be subjected to any complex deformation, including twisting.

Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University’s McCormick School of Engineering and Applied Science, and John Rogers, the Flory-Founder Chair Professor of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, have improved their so-called “pop-up” technology to create circuits that can be twisted. Such electronics could be used in places where flat, unbending electronics would fail, like on the human body.

Their research is published online by the Proceedings of the National Academy of Sciences (PNAS).

Electronic components historically have been flat and unbendable because silicon, the principal component of all electronics, is brittle and inflexible. Any significant bending or stretching renders an electronic device useless.

Huang and Rogers developed a method to fabricate stretchable electronics that increases the stretching range (as much as 140 percent) and allows the user to subject circuits to extreme twisting. This emerging technology promises new flexible sensors, transmitters, new photovoltaic and microfluidic devices, and other applications for medical and athletic use.

The partnership — where Huang focuses on theory, and Rogers focuses on experiments — has been fruitful for the past several years. Back in 2005, the pair developed a one-dimensional, stretchable form of single-crystal silicon that could be stretched in one direction without altering its electrical properties; the results were published by the journal Science in 2006. Earlier this year they made stretchable integrated circuits, work also published in Science.

Next, the researchers developed a new kind of technology that allowed circuits to be placed on a curved surface. That technology used an array of circuit elements approximately 100 micrometers square that were connected by metal “pop-up bridges.”

The circuit elements were so small that when placed on a curved surface, they didn’t bend — similar to how buildings don’t bend on the curved Earth. The system worked because these elements were connected by metal wires that popped up when bent or stretched. The research was the cover article in Nature in early August.

In the research reported in PNAS, Huang and Rogers took their pop-up bridges and made them into an “S” shape, which, in addition to bending and stretching, have enough give that they can be twisted as well.

“For a lot of applications related to the human body — like placing a sensor on the body — an electronic device needs not only to bend and stretch but also to twist,” said Huang. “So we improved our pop-up technology to accommodate this. Now it can accommodate any deformation.”

Huang and Rogers now are focusing their research on another important application of this technology: solar panels. The pair published a cover article in Nature Materials this month describing a new process of creating very thin silicon solar cells that can be combined in flexible and transparent arrays.

Just two weeks after a Nobel Prize was given to a theoretical work on subatomic particles, scientists are announcing a discovery about a much more familiar form of matter: Scotch tape. It turns out that if you peel the popular adhesive tape off its roll in a vacuum chamber, it emits X-rays. The researchers even made an X-ray image of one of their fingers.

Who knew? Actually, more than 50 years ago, some Russian scientists reported evidence of X-rays from peeling sticky tape off glass. But the new work demonstrates that you can get a lot of X-rays, a study co-author says.

“We were very surprised,” said Juan Escobar. “The power you could get from just peeling tape was enormous.”

Escobar is a graduate student at the University of California, Los Angeles.

He suggests that with some tune-ups, the process might be harnessed for making inexpensive X-ray machines for paramedics or for places where electricity is expensive or hard to get. After all, you could peel tape or do something similar in such machines with just human power, like cranking.

In the new work, a machine is peeling a standard Scotch tape off a roll in a vacuum chamber at about 1.2 inches per second. Rapid pulses of X-rays, each about a billionth of a second long, emerged from very close to where the tape was coming off the roll.

This seems an interesting idea for generating X-Rays, especially in low cost instrumentation. Imagine third-world countries having cheap X-Rays machines in their hospitals…
via AP

Researchers from McGill University in the US, from the Ultra-Low Temperature Condensed Matter Experiment Lab, led by Dr. Guillaume Gervais discovered a new state of matter, a quasi-three- dimensional electron crystal, in a material very much like those used in the fabrication of modern transistors. This discovery could have huge implications for the development of new electronic devices.

Two-dimensional electron crystals were discovered in the laboratory in the 1990s, and were predicted as far back as 1934 by renowned Hungarian physicist Eugene Wigner. Until an accidental discovery during one of Gervais’s earliest ultra-low temperature experiments in 2005, however, no one predicted the existence of quasi-three-dimensional electron crystals. “Picture a sandwich, and the ham in the middle is your electrons,” explained Dr. Guillaume Gervais, director of McGill’s Ultra-Low Temperature Condensed Matter Experiment Lab. “In a 2D electron crystal, the electrons are squeezed between two materials and they’re very two dimensional. They can move on a plane, like billiard balls on a pool table, but there’s no up and down motion. There’s a thickness, but they’re stuck.”

Working with one of the purest semiconductor materials ever made, they discovered the quasi-three-dimensional electron crystal in a device cooled at ultra-low temperatures roughly 100 times colder than intergalactic space. The material was then exposed to the most powerful continuous magnetic fields generated on Earth.

When you go to lower scales with the electronic circuits currently being used, other laws of physics apply. Once in two years, the circuits density gets higher, and there will be a time not too far away when it will be impossible to make electronics any smaller. Being so small, the electrons cannot be treated by the classic laws of physics, they respect other weird laws, the quantum physics. For example, at those scales they’re not to be treated as individual units, because they may even split up.

“This issue is academic, but it’s not just academic.”, says Gervais. “The same semiconductor materials we’re working with are currently used in cellphones and other electronic devices. We need to understand quantum effects so we can use them to our own advantage and perhaps reinvent the transistor altogether. That way, progress in electronics will keep happening .”