Scientists from the University of Chicago and the University of Wisconsin have unexpectedly created a new type of glass that could improve the efficiency of optical fibers, solar cells, light-emitting diodes, and other electronic devices.
The discovery, which is reported in the latest edition of the journal Proceedings of the National Academy of Sciences, demonstrates a degree of molecular order in a type of material believed to be completely amorphous and random, study co-author Juan de Pablo explained.
De Pablo, a theorist who performed computer simulations as part of a group led by Wisconsin professor Mark Ediger, told redOrbit via email that the new glass was “ultrastable, mechanically strong and had anisotropic optical properties.” In a statement, he and his colleagues said that the results were surprising, as randomness was believed to be a defining characteristic of glass.
They realized that they had come up with a new type of glass after attempting to explain unusual peaks in what they thought should have been featureless optical data. While attempting to correct perceived errors in calculations, they realized that they had found a new type of glass.
Temperature, creation method explain properties of new glass
Ediger, de Pablo, and their team members vaporized large organic molecules in a high vacuum, then slowly deposited them onto a substrate at precisely controlled temperatures in thin layers to create the glass. Once the sample was thick enough, they used a technique known as spectroscopic ellipsometry to analyze how light and laser radiation interacted with it.
They discovered peaks in the material, which typically only appear when said material possesses some type of distinct, organized molecular orientation, de Pablo said. They were initially unable to explain the origins of these peaks, or why their appearance seemed to rely on the temperatures at which the glass formed. Computer simulations revealed that a percentage of the molecules in the glass were aligning themselves in unison, but the study authors still did not know why.
What they ultimately discovered is that the answer was in the way the materials were created. In liquids such as glass, surface molecules act with other molecules in the air, sometimes packing together and lining up in a pattern different than the randomly arrayed ones found in most of the material. The vapor deposition process used by the researchers essentially places one layer on top of another, trapping molecules previously on the surface.
In order for this to happen, the researchers discovered that the glass needed to be grown in the relatively narrow temperature range where liquids change into solid-like glasses. By altering the temperature, they were able to fine-tune the degree of order, and once the deposition process ended, the material became relatively stable and resistant to hotter and/or colder conditions.
De Pablo told redOrbit that he and his colleagues “are now improving our ability to control stable glasses, and several interesting and unexpected findings are being examined in more detail before we publicize the results.”
(Image credit: University of Chicago)
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