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Feb 23, 2016 0    2
Just add water
Molecular Light Switch

What follows is an abridged version of an article that first appeared on DrexlerNOW.  A link to the original article can be found below.

A bit of stray moisture during an experiment tipped off scientists about the strange behavior of a complex oxide material they were studying—shedding light on its potential for improving chemical sensors, computing and information storage. In the presence of a water molecule on its surface, the layered material emits ultraviolet light from its interior. A team of researchers from Drexel University, the University of Pennsylvania, the University of California at Berkeley, and Temple University recently published its discovery that it is possible to control ultraviolet light production via a chemical reaction that functions like flipping a light switch.

While studying a sample of lanthanum aluminate film on a strontinum titanate crystal, the team discovered that the sample was beginning to emit intense levels of UV light. Carefully reproducing the experimental conditions helped them realize that water molecules might be playing a role in the UV light being emitted from inside the material.

Said Spanier, “This discovery is quite remarkable because we uncovered a chemical reaction at the surface that prompts the emission of light from the interface [between layers] within—and we are able to turn it off and on again. Amazingly, we can also make it stronger by increasing the distance between the molecules and surface and the buried interface, by using thicker films for example.”

“Dissociation of water fragments on the oxide surface releases electrons that move to the buried interface,” researcher Fenggong Wang explained. This is the first report of the introduction of molecules to the surface controlling the emission of light—of any color—from a buried solid-surface interface.

“We suspect that the material could be used for simple devices like transistors and sensors. By strategically placing molecules on the surface, the UV light could be used to relay information—much the way computer memory uses a magnetic field to write and rewrite itself, but with the significant advantage of doing it without an electric current,” said Mohammad Islam, an assistant professor from the State University of New York at Oswego.

TAGS: #complex oxides    #crystals    #photoemission    #thin films