Tag Archives: Semiconductors/Nanotechnology

Ultrasensitive Microscope Reveals How Charging Changes Molecular Structures

Post Syndicated from Dexter Johnson original https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/structural-changes-of-molecules-during-charging-revealed

New ability to image molecules under charging promises big changes for molecular electronics and organic photovolatics

All living systems depend on the charging and discharging of molecules to convert and transport energy. While science has revealed many of the fundamental mechanisms of how this occurs, one area has remained shrouded in mystery: How does a molecule’s structure change while charging? The answer could have implications for range of applications including molecular electronics and organic photovoltaics.

Now a team of researchers from IBM Research in Zurich, the University of Santiago de Compostela and ExxonMobil has reported in the journal Science the ability to image, with unprecedented resolution, the structural changes that occur to individual molecules upon charging.

This ability to peer into this previously unobserved phenomenon should reveal the molecular charge-function relationships and how they relate to biological systems converting and transporting energy. This understanding could play a critical role in the development of both organic electronic and photovoltaic devices.

“Molecular charge transition is at the heart of many important phenomena, such as photoconversion, energy and molecular transport, catalysis, chemical synthesis, molecular electronics, to name some,” said Leo Gross, research staff member at IBM Zurich and co-author of the research. “Improving our understanding of how the charging affects the structure and function of molecules will improve our understanding of these fundamental phenomena.”

This latest breakthrough is based on research going back 10 years when Gross and his colleagues developed a technique to resolve the structure of molecules with an atomic force microscope. AFMs map the surface of a material by recording the vertical displacement necessary to maintain a constant force on the cantilevered probe tip as it scans a sample’s surface.

Over the years, Gross and his colleagues refined the technique so it could see the charge distribution inside a molecule, and then were able to get it to distinguish between individual bonds of a molecule.

The trick to these techniques was to functionalize the tip of the AFM probe with a single carbon monoxide (CO) molecule. Last year, Gross and his colleague Shadi Fatayer at IBM Zurich believed that the ultra-high resolution possible with the CO tips could be combined with controlling the charge of the molecule being imaged.

“The main hurdle was in combining two capabilities, the control and manipulation of the charge states of molecules and the imaging of molecules with atomic resolution,” said Fatayer.

The concern was that the functionalization of the tip would not be able to withstand the applied bias voltages used in the experiment. Despite these concerns, Fatayer explained that they were able to overcome the challenges in combining these two capabilities by using multi-layer insulating films, which avoid charge leakage and allow charge state control of molecules.

The researchers were able to control the charge-state by attaching single electrons from the AFM tip to the molecule, or vice-versa. This was achieved by applying a voltage between the tip and the molecule. “We know when an electron is attached or removed from the molecule by observing changes in the force signal,” said Fatayer.

The IBM researchers expect that this research could have an impact in the fundamental understanding of single-electron based and molecular devices. This field of molecular electronics promises a day when individual molecules become the building blocks of electronics.

Another important prospect of the research, according to Fatayer and Gross, would be its impact on organic photovoltaic devices. Organic photovoltaics have been a tantalizing solution for solar power because they are cheap to manufacture. However, organic solar cells have been notoriously poor compared to silicon solar cells at converting sunlight to energy efficiently.

The hope is that by revealing how the structural changes of molecules under charge impact the charge transition of molecules, engineers will be able to further optimize organic photovoltaics.

Is Graphene by Any Other Name Still Graphene?

Post Syndicated from Dexter Johnson original https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/is-graphene-by-any-other-name-still-graphene

Consumers may finally have a way to know if their graphene-enabled products actually get any benefit from the wonder material

Last year, the graphene community was rocked by a series of critical articles that appeared in some high-profile journals. First there was an Advanced Material’s article with the rather innocuously title: “The Worldwide Graphene Flake Production”. It was perhaps the follow-up article that appeared in the journal Nature that really shook things up with its incendiary title: “The war on fake graphene”.

In these two articles it was revealed that material that had been claimed to be high-quality (and high-priced) graphene was little more than graphite powder. Boosted by their appearance in high-impact journals, these articles threatened the foundations of the graphene marketplace.

But while these articles triggered a lot of hand wringing among the buyers and sellers of graphene, it’s not clear that their impact extended much beyond the supply chain of graphene. Whether or not graphene has aggregated back to being graphite is one question. An even bigger one is whether or not consumers are actually being sold a better product on the basis that it incorporates graphene. 

Consumer products featuring graphene today include everything from headphones to light bulbs. Consequently, there is already confusion among buyers about the tangible benefits graphene is supposed to provide. And of course the situation becomes even worse if the graphene sold to make products may not even be graphene: how are consumers supposed to determine whether graphene infuses their products with anything other than a buzzword?

Another source of confusion arises because when graphene is incorporated into a product it is effectively a different animal from graphene in isolation. There is ample scientific evidence that graphene when included in a material matrix, like a polymer or even paper, can impart new properties to the materials. “You can transfer some very useful properties of graphene into other materials by adding graphene, but just because the resultant material contains graphene it does not mean it will behave like free-standing graphene, explains Tom Eldridge, of UK-based Fullerex, a consultancy that provides companies with information on how to include graphene in a material matrix.

Eldridge added: “This is why it is often misleading to talk about the superlative properties of free-standing graphene for benefiting applications, because almost always graphene is being combined with other materials. For instance, if I combine graphene with concrete I will not get concrete which is 200 times stronger than steel.”

This is what leaves consumers a bit lost at sea: Graphene can provide performance improvements to a product, but what kind and by how much?

The Graphene Council (Disclosure: The author of this story has also worked for The Graphene Council) recognized this knowledge gap in the market and has just launched a “Verified Graphene Product” Program in addition to its “Verified Graphene Producer” program. The Verified Graphene Producer program takes raw samples of graphene and characterizes them to verify the type of graphene it is, while the Verified Graphene Product program addresses the issue of what graphene is actually doing in products that claim to use it. 

Companies that are marketing products that claim to be enhanced by graphene can use this service, and the verification can be applied to their product to give buyers confidence that graphene is actually doing something. (It’s not known if there are any clients taking advantage of it yet.)

“Consumers want to know that the products they purchase are genuine and will perform as advertised,” said Terrance Barkan, executive director of The Graphene Council. “This applies equally to purchasers of graphene enhanced materials and applications. This is why independent, third-party verification is needed.”

Magnet Sets World Record at 45.5 Teslas

Post Syndicated from Mark Anderson original https://spectrum.ieee.org/tech-talk/semiconductors/nanotechnology/a-beachhead-to-superstrong-magnetic-fields

It’s the strongest continuous DC magnetic field ever recorded and could help scientists study nuclear fusion and exotic states of matter

A new multicomponent, partially-superconducting electromagnet—currently the world’s strongest DC magnet of any kind—is poised to reveal a path to substantially stronger magnets still. The new magnet technology could help scientists study many other phenomena including nuclear fusion, exotic states of matter“shape-shifting” molecules, and interplanetary rockets, to name a few.

The National High Magnetic Field Laboratory in Tallahassee, Florida is home to four types of advanced, ultra-strong magnets. One supports magnetic resonance studies. Another is configured for mass spectrometry. And a different type produces the strongest magnetic fields in the world. (Sister MagLab campuses at the University of Florida and Los Alamos National Laboratory provide three more high-capacity magnets for other fields of study.)

It’s that last category on the Tallahassee campus—world’s strongest magnet—that the latest research is attempting to complement. The so-called MagLab DC Field Facility, in operation since 1999, is nearing a limit in the strength of magnetic fields it can produce with its current materials and technology.

The MagLab’s DC magnet maintains a steady 45 Tesla of field strength, which until very recently was the strongest continuous magnetic field produced in the world. (Not to be confused with the electric car brand of the same name, Tesla is also a unit of magnetic field strength. The higher its Tesla rating, the stronger the magnet. For comparison, a typical MRI machine is built around a superconducting magnet with approximately 3 Tesla of field strength. The Earth’s magnetic field, felt at the planet’s surface, is 0.00005 T.)

A Faster Way to Rearrange Atoms Could Lead to Powerful Quantum Sensors

Post Syndicated from Mark Anderson original https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/a-faster-way-to-rearrange-atoms

The technique is also more accurate than the traditional method of poking atoms with the tip of a scanning electron microscope

The fine art of adding impurities to silicon wafers lies at the heart of semiconductor engineering and, with it, much of the computer industry. But this fine art isn’t yet so finely tuned that engineers can manipulate impurities down to the level of individual atoms.

As technology scales down to the nanometer size and smaller, though, the placement of individual impurities will become increasingly significant. Which makes interesting the announcement last month that scientists can now rearrange individual impurities (in this case, single phosphorous atoms) in a sheet of graphene by using electron beams to knock them around like croquet balls on a field of grass.

The finding suggests a new vanguard of single-atom electronic engineering. Says research team member Ju Li, professor of nuclear science and engineering at MIT, gone are the days when individual atoms can only be moved around mechanically—often clumsily on the tip of a scanning tunneling microscope.

Europe Has Invested €1 Billion Into Graphene—But For What?

Post Syndicated from Dexter Johnson original https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/europe-has-invested-1-billion-into-graphenebut-for-what

Six years into an ambitious 10-year research project, experts weigh in on whether the Graphene Flagship can help the “wonder material” make it through the Valley of Death

Six years ago, the European Union (EU) embarked on an ambitious project to create a kind of Silicon Valley for the “wonder material” of the last decade: graphene. The project—called the Graphene Flagship—would leverage €1 billion over 10 years to push graphene into commercial markets. The project would bring together academic and industrial research institutes to not only ensure graphene research would be commercialized, but to also make Europe an economic powerhouse for graphene-based technologies.

To this day, the EU’s investment in the Graphene Flagship represents the single largest project in graphene research and development (though some speculate that graphene-related projects in China may have surpassed it). In the past six years, the Graphene Flagship has spawned nine companies and 46 new graphene-based products. Despite these achievements, there remains a sense among critics that the wonder material has not lived up to expectations and the Flagship’s efforts have not done much to change that perception.

Graphene’s unique properties have engendered high expectations in a host of areas, including for advanced composites and new types of electronic devices. While graphene can come in many forms, its purest form is that of a one-atom-thick layer of graphite. This structure has provided the highest thermal conductivity ever recorded—10 times higher than copper. It also has one of the highest intrinsic electron mobilities of any material (the speed at which electrons can travel through a material), which is approximately 100 times greater than silicon—a tantalizing property for electronic applications.

The Graphene Flagship is now more than halfway through its 10-year funding cycle. To many observers, the project’s achievements—or lack thereof—is a barometer for the commercial status of graphene, which was first synthesized at the UK’s University of Manchester in 2004, earning its discoverers the Nobel Prize in 2010. When it was founded, the Flagship wrestled with a key question that it still faces today: Was the Flagship set up to support “fundamental” research or “applied” research in its quest to make Europe the “Graphene Valley” of the world?