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Light Reveals the Spin of Electrons

Spintronics—in which the spin of electrons is used to encode information rather than chargeis the foundational technology for the read heads in the hard drives of our computers and is the focus of extensive research in creating the logic devices based on the spin of electrons that could lead to quantum computing.

While there has been some recent research in which electric fields are used to manipulate the spin of electrons, the predominant way to read the spin of an electron is to use extremely powerful magnetic fields.

Now researchers at the London Centre for Nanotechnology (LCN) have put aside both magnetic and electrical fields and have demonstrated that it’s possible to read the spin of an electron with a laser.

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Novel Process Promises Atomically Thin Semiconductors for Electronics

Researchers at Cornell University have developed a process for producing transition metal dichalcogenides (TMDs) with spatial uniformity—a key attribute for thin films in electronics—on wafers. This development could ultimately translate into atomically thin semicondutor layers that could pave the way for atomic-scale minutarization of electronics.

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“Holey” Graphene Improved as an Electrode Material

Researchers at the University of California San Diego (UCSD) have developed a method for increasing the amount of electric charge that graphene can store as an electrode material in supercapacitors.  The key to what the researchers have done is making the graphene “holey.”

The UCSD team is not the first to recognize the merits of “holey” graphene. Last year, researchers at the California NanoSystems Institute (CNSI) at UCLA developed what they termed a “holey graphene framework;” they claimed that it significantly boosted the energy density of supercapacitors.  The CNSI researchers concluded that an energy density of a fully packaged device stack based on the holey-graphene framework is capable of energy densities as high as 35 watt-hours per kilogram, which compares favorably to today’s upper average supercapacitor, which can get around 28 Wh/kg.

The UCSD team told IEEE Spectrum that in their latest research, they created "holes" that are of the order of 1 nanometer in size, while the work from the UCLA paper reports pores that are 1000 times larger. Consequently, there are more holes in the UCSD samples, implying greater charge density per unit area or volume of material.

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Graphene Could Enable Holographic 3-D Imaging on a Mobile Device

Last year, we covered research that was promising to bring new life to 3-D TV by eliminating the need for special glasses to see the 3-D effect.

That work proposed at the University of Central Florida (UCF) was going to pursue nanoprinting techniques that would turn polymers into 3-D holographic displays that functioned much like Princess Leia’s message in Star Wars. In theory, the proposed technology would involve a stationary table projecting the holograms.

Now researchers at Swinburne University of Technology in Australia are leveraging graphene to get a similar effect with a mobile device. 

“Our technique can be leveraged to achieve compact and versatile optical components for controlling light,” said Min Gu, director of Swinburne’s Centre for Micro-Photonics, in a press release. “We can create the wide angle display necessary for mobile phones and tablets.”

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3-D Printed Graphene Aerogels Could Improve Sensors and Batteries

Aerogels have long been one of those ‘gee whiz’ materials that gets people to take notice—watching a solid float on air tends to do that. To accomplish their remarkable feats, aerogels are essentially a gel in which the liquid component of the gel has been replaced with gas. We’ve seen them used in applications from “invisibility cloaks” to oil spill remediation.

Now researchers at Lawrence Livermore National Laboratory (LLNL) have produced an aerogel out of graphene that could have applications ranging from electronics to energy storage. Boosting the ‘gee whiz’ factor: the new material is produced through 3-D printing.

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New Material Can Change Its Color and Texture Like a Cuttlefish

Nanomaterials have offered scientists a variety of ways to pursue biomimicry. We’ve seen nanorods used in polymers to mimic the ability of amphibians to grow back lost limbs or to duplicate the adhesive properties used by geckos when they walk on ceilings.

Now researchers at the University of Nebraska-Lincoln (UNL) have looked at the camouflage capabilities of the cuttlefish to develop a structure than can change both its color and texture within seconds of being exposed to pulses of light.

"Changing color is relatively easy; a TV can do that,” said Li Tan, an associate professor a UNL, in a press release. “Changing texture is harder. We wanted to combine the two."

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Molybdenum Disulfide Gets a Boost as a Li-ion Electrode Material

While the prospect of aluminum-ion batteries may have received a lift recently, the workhorse battery for both our handheld electronic devices and our electric vehicles remains the ubiquitous lithium-ion (Li-ion) battery.

And now, researchers at Kansas State University (KSU) have taken a fresh look at the venerable Li-ion battery: Using the two-dimensional material molybdenum disulfide (MoS2) on its electrodes, they say, may dramatically boost its storage capacity. What they have come up with is a hybrid material that combines MoS2 with silicon carbonitride (SiCN); it can store double the charge of electrodes using MoS2 on its own.

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Graphene Brings Photodetectors to the Brink of Terahertz Speeds

Researchers at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain have been at the forefront of exploiting graphene’s optoelectronic capabilities.

The latest research out of ICFO has demonstrated a graphene-based ultrafast photodetector that can convert absorbed light into an electrical voltage at speeds of less than 50 femtoseconds. How fast is that? A femtosecond is a thousandth of a millionth of a millionth of a second. So fast—ultrafast.

In research published in the journal Nature Nanotechnology, the ICFO team addressed the niggling issue in graphene-based photothermoelectric devices, specifically charge carrier cooling times, which has limited their switching speeds.

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Perovskite Leads to 100-Percent Efficient Nanowire Lasers

Last year, perovskites established themselves as the “next big thing” in photovoltaic materials, with energy conversion efficiency numbers reaching as high as 20 percent.

Now researchers at the University of Wisconsin-Madison have demonstrated that perovskites can produce high-efficiency, ultra small lasers.

“While most researchers make these perovskite compounds into thin films for the fabrication of solar cells, we have developed an extremely simple method to grow them into elongated crystals that make extremely promising lasers,” said Song Jin, a professor at the University of Wisconsin-Madison, in a press release.

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Graphene Could Be Great for Spintronics

Graphene did not immediately impress anybody with its potential in the field of spintronics, the use of the spin of electrons to encode information rather than charge. If you laid graphene out flat, it didn’t appear to influence electron spin,  that property remained random rather than patterned. But that all changed when scientists saw what happens when you put a small bend in the graphene.

Since then, there’s been a steady stream of research looking at the capabilities of graphene in spintronic applications.  The latest, and perhaps most significant development, is news that researchers at Chalmers University of Technology in Sweden have been able to preserve electron spin for an extended distance using large area graphene.

"We believe that these results will attract a lot of attention in the research community and put graphene on the map for applications in spintronic components," said Saroj Dash, one of the Chalmers researchers, in a press release.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
Contributor
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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