Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Watching the hidden life of materials

28.10.2014

Ultrafast electron diffraction experiments open a new window on the microscopic world

Researchers at McGill University have succeeded in simultaneously observing the reorganizations of atomic positions and electron distribution during the transformation of the “smart material” vanadium dioxide (VO2) from a semiconductor into a metal – in a time frame a trillion times faster than the blink of an eye. 


Prof. Siwick tweaking up the laser in his McGill University lab. CREDIT: Allen McInnis for McGill University

The results, reported Oct. 24 in Science, mark the first time that experiments have been able to distinguish changes in a material’s atomic-lattice structure from the relocation of the electrons in such a blazingly fast process.

The measurements were achieved thanks to the McGill team’s development of instrumentation that could be used by scientists in a variety of disciplines: to examine the fleeting but crucial transformations during chemical reactions, for example, or to enable biologists to obtain an atomic-level understanding of protein function. This ultrafast instrumentation combines tools and techniques of electron microscopy with those of laser spectroscopy in novel ways. 

“We’ve developed instruments and approaches that allow us to actually look into the microscopic structure of matter, on femtosecond time scales (one millionth of a billionth of a second) that are fundamental to processes in chemistry, materials science, condensed-matter physics, and biology,” says Bradley Siwick, the Canada Research Chair in Ultrafast Science at McGill.

“We’re able to both watch where nuclei go, and separate that from what’s happening with the electrons,” says Siwick, an associate professor in the departments of Chemistry and Physics. “And, on top of that, we are able to say what impact those structural changes have on the property of the material. That’s what’s really important technologically.”

By taking advantage of these recent advances, the research group has shed new light on a long-standing problem in condensed matter physics. The semiconductor-metal transition in Vanadium dioxide has intrigued the scientific community since the late 1950s.The material acts as a semiconductor at low temperatures but transforms to a highly conductive metal when temperature rises to around 60 degrees Celsius – not that much warmer than room temperature. This unusual quality gives the material the potential to be used in a range of applications, from high-speed optical switches to heat-sensitive smart coatings on windows.

The experiments took place in Siwick’s lab in the basement of McGill’s Chemistry building, where he and his team of grad students spent nearly four years painstakingly assembling a maze of lasers, amplifiers and lenses alongside an in-house designed and built electron microscope on a vibration-free steel table.

To conduct the experiments, the McGill team collaborated with the research group of Mohamed Chaker at INRS EMT, a university research centre outside Montreal. The INRS scientists provided the high quality, extremely thin samples of VO2 – about 70 nanometers, or 1000 times smaller than the width of a human hair– required to make ultrafast electron diffraction measurements.

The diffraction patterns provide atomic-length-scale snapshots of the material structure at specific moments during rearrangement. A series of such snapshots, run together, effectively creates a kind of movie, much like an old-fashioned flip book. 

 “This opens a whole new window on the microscopic world that we hope will answer many outstanding questions in materials and molecular physics, but also uncover at least as many surprises.  When you look with new eyes you have a chance to see things in new ways,” Siwick says.

The research was supported by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs program, and the Fonds du Recherche du Quèbec-Nature et Technologies.

``A photoinduced metal-like phase of monoclinic VO2 revealed by ultrafast electron diffraction``, Vance R. Morrison, Robert P. Chatelain et al, Science, Oct. 24, 2014.
DOI: 10.1126/science.1253779
http://www.sciencemag.org/content/346/6208/445.full 

Contact Information

Contact: Prof. Bradley Siwick
Organization: Departments of Physics and Chemistry

Secondary Contact Information

Contact: Chris Chipello
Organization: Media Relations Office
Office Phone: 514-398-4201

Chris Chipello | Eurek Alert!
Further information:
http://www.mcgill.ca/newsroom/channels/news/watching-hidden-life-materials-239767

Further reports about: Electrons INRS McGill VO2 dioxide experiments materials microscopic physics semiconductor snapshots structure

More articles from Materials Sciences:

nachricht Gelatine instead of forearm
19.04.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Computers create recipe for two new magnetic materials
18.04.2017 | Duke University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>