New research could enable “selfies” of solids

Posted on Wednesday, June 24, 2015

Ottawa researchers have recently discovered that it's possible to examine solids from the inside, with “selfies” and movies that capture how semiconductor devices operate. The findings, published this week in Nature, will help make it possible to design better devices by making it possible to measure the voltages that switch in the integrated circuit of cellular phones and computers. These findings could allow scientists to measure the behaviour of materials under extreme conditions, similar to those found at the centre of the Earth.

When an intense light wave and an atom (or molecule) meet, the light can temporally dislodge one of the atom's electrons. If the atom is reunited with its lost electron, it emits light in the form of the world's shortest light pulse — measured in attoseconds, or 1/1,000,000,000,000,000,000 (one billionth of a billionth) of a second. Though the engineering of this seemingly unlikely scenario and the use a gas of molecules, it is now possible for science to reach pulses short enough to freeze the motion of an electron in a molecule. And the molecule simultaneously snaps a “selfie,” with the image being carried by the emitted light.

“When the experiment began, we thought that if we could transfer this technology from gases to solids, we could integrate attosecond devices with semiconductor technology,” explains Paul Corkum, NRC-Canada Research Chair in Attosecond Photonics and physics professor at the University of Ottawa. “However, although it seemed unlikely that the gas could be replaced because the electron would need to dodge the many other atoms of a solid before reuniting with its parent ion — called a “hole” by physicists, the experiment showed otherwise.” In fact, if an electron is liberated in a solid, the electron and the hole are both caught by the light wave. Both dodge the neighbouring atoms, almost as if they had no neighbours.

The University of Ottawa and the National Research Council have joined together to form the Joint Attosecond Science Lab (JASLab), specifically to develop attosecond science. Giulio Vampa, a PhD student at the JASLab, became so interested in this experiment that he turned to one of the world's top scientists working in theory of photonics, University of Ottawa professor Thomas Brabec, for help with calculations.

“As it became clear that we had a realistic shot at developing attosecond science in solids, we turned to the world-class Advanced Laser Light Source (ALLS) in Montreal and the team at Institut national de la recherche scientifique(INRS) led by INRS professor François Légaré. With the best combination of people and facilities in the world, we're positioned to reap the technological benefits that come with leadership,” says Professor Corkum.

The full study was published in this week's issue of Nature.

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