The iridescent yellow ring with emerald flakes around the edges seen in this micrograph is (NH4)2WS4. John Allen, an undergraduate researcher at the University of Georgia, says the ring formed when a solution of (NH4)2WS4 in a water was drop-cast onto a silicon wafer for creating WS2 thin films; the amorphous boundary resulted from capillary and drying forces. Allen’s and coworkers are studying WS2 thin film formation by creating and testing various solutions to see how they affect properties such as thickness. Thin films such as these have applications in optoelectronics—for example, in photo detectors.
Submitted by John Allen
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