Researchers Report Switching Material Between Semiconductor And Metallic States
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A group of researchers from the Fritz Haber Institute of the Max Planck Society and the Humboldt-Universitat zu Berlin have found out that a semiconductor can be converted to a metal and back by light more easily and more quickly than previously thought. This discovery may increase the processing speed and simplify the design of many common technological devices.
[...] The scientists involved in this study have investigated the popular semiconductor zinc oxide and figured out that by illuminating it with a laser, the semiconductor surface can be turned into a metal-and back again. This "photo-doping" is achieved by photoexcitation: The light modifies the electronic properties such that electrons suddenly move freely and an electrical current can flow, as it would in metal. Once the light is switched back off, the material also quickly goes back to being a semiconductor.
"This mechanism is a completely new and surprising discovery," says Lukas Gierster, lead author and Ph.D. student in Stahler's group. "Three things in particular have surprised us: For one, photo- and chemical doping behave so much alike despite being fundamentally different mechanisms; two, gigantic changes can be reached with very low laser power; and three, switching the metal on and off happens quickly."
[...] This discovery could be highly beneficial for high-frequency device applications and ultrafast optically controlled transistors by increasing processing speed and simplifying device design. "Our gadgets could become faster-and thus smarter," Julia Stahler says and adds: "Low-power, ultrafast switching of conduction properties will provide us with high speed and design flexibility." She and her group are convinced that the same will prove true for other semiconducting materials, so that their discovery will likely reach much further than just zinc oxide.
Journal Reference:
L. Gierster, S. Vempati, J. Stahler. Ultrafast generation and decay of a surface metal [open], Nature Communications (DOI: 10.1038/s41467-021-21203-6)
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