Solving the vanadium dioxide conundrum
18 Dec 2014 by Evoluted New Media
Researchers have shed new light on a long standing conundrum in condensed-matter physics by combining electron microscopy and laser spectroscopy in novel ways.
Vanadium dioxide has intrigued the scientific community since the late 1950s; it acts as a semiconductor at low temperatures, but transforms into a highly conductive metal at around 60°C, meaning a range of potential applications from high-speed optical switches to heat sensitive smart coatings.
Researchers at McGill University have developed instrumentation uniting electron microscopy and laser spectroscopy which has enabled them to observe the reorganisation of atomic positions and electron distribution during this change in a time frame a trillion times faster than the blink of an eye.
“We’ve developed instruments and approaches that allow us to actually look into the microscopic structure of matter, on femtosecond time scales that are fundamental to processes in chemistry, materials science, condensed-matter physics and biology,” said Professor Bradley Siwick, associate professor in the departments of Chemistry and Physics at McGill.
“We’re able to both watch where nuclei go, and separate that from what’s happening with the electrons. 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.”
The team collaborated with INRS EMT, who provided the high quality samples of vanadium dioxide required to make ultrafast electron diffraction measurements. The resulting diffraction patterns provide atomic-length-scale snapshots of the material structure at specific moments during rearrangement.
“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,” said Siwick. “When you look with new eyes you have the chance to see things in new ways.”
A photoinduced metal-like phase of monoclinic VO2 revealed by ultrafast electron diffraction
