Volume 90 Issue 25 | p. 33 | Concentrates
Issue Date: June 18, 2012

Laser Method Yields Single-Atom-Thick Molybdenum Sulfide

Simple technique could lead to molybdenum sulfide-based electronics
Department: Science & Technology
News Channels: Nano SCENE, Materials SCENE
Keywords: molybdenum disulfide, MoS2, graphene, transistors, electronic devices, band gap
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An optical micrograph shows a MoS2 flake before (left) and after laser thinning. Where MoS2 is multiple layers thick, it appears blue; single-layer MoS2 is purple.
Credit: Nano Lett.
An optical microscope image shows a molybdenum disulfide flake before (left) and after (right) a 10-mW laser scans a rectangular region (yellow outline). Where MoS2 is multiple layers thick, it appears blue; single-layer MoS2 is purple; and the silicon dioxide substrate is light brown.
 
An optical micrograph shows a MoS2 flake before (left) and after laser thinning. Where MoS2 is multiple layers thick, it appears blue; single-layer MoS2 is purple.
Credit: Nano Lett.

A laser-based technique can make one-atom-thick layers of molybdenum disulfide, possibly enabling large-scale production of electronics based on the semiconductor (Nano Lett., DOI: 10.1021/nl301164v). Single-atom-thick MoS2 has a band gap—the energy difference between a conducting state and a nonconducting one—greater than silicon’s. As a result, transistors made from the material would require less power to turn off than silicon-based ones do. Researchers think the flexible and transparent material could be an alternative to silicon in bendable displays and electronics. Currently, methods to make single-atom sheets of MoS2, such as exfoliating chunks of the material using sticky tape, are too cumbersome for large-scale production. Andres Castellanos-Gomez, a researcher at Delft University of Technology, in the Netherlands, found that when he shined a 10-mW green laser beam on multilayer MoS2 flakes, the material’s top layers vaporized. He and his colleagues used optical microscopy, atomic force microscopy, and Raman spectroscopy to confirm that the remaining material was a single layer of atoms. They produced transistors using the material and found that the devices had switching speeds similar to those of transistors made from exfoliated single-layer flakes.

 
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