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Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

DOI: 10.1021/acs.nanolett.6b04775 DOI Help

Authors: Mingu Kang (Pohang University of Science and Technology) , Beomyoung Kim (Pohang University of Science and Technology; Advanced Light Source) , Sae Hee Ryu (Pohang University of Science and Technology) , Sung Won Jung (Pohang University of Science and Technology) , Jimin Kim (Pohang University of Science and Technology) , Luca Moreschini (Pohang University of Science and Technology; Advanced Light Source) , Chris Jozwiak (Advanced Light Source) , Eli Rotenberg (Advanced Light Source) , Aaron Bostwick (Advanced Light Source) , Keun Su Kim (Pohang University of Science and Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nano Letters

State: Published (Approved)
Published: February 2017
Diamond Proposal Number(s): 13946

Abstract: van der Waals two-dimensional (2D) semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic band gap. For realistic applications, the ideal is to modify the band gap in a controlled manner by a mechanism that can be generally applied to this class of materials. Here, we report the observation of a universally tunable band gap in the family of bulk 2H transition metal dichalcogenides (TMDs) by in situ surface doping of Rb atoms. A series of angle-resolved photoemission spectra unexceptionally shows that the band gap of TMDs at the zone corners is modulated in the range of 0.8–2.0 eV, which covers a wide spectral range from visible to near-infrared, with a tendency from indirect to direct band gap. A key clue to understanding the mechanism of this band-gap engineering is provided by the spectroscopic signature of symmetry breaking and resultant spin-splitting, which can be explained by the formation of 2D electric dipole layers within the surface bilayer of TMDs. Our results establish the surface Stark effect as a universal mechanism of band-gap engineering on the basis of the strong 2D nature of van der Waals semiconductors.

Journal Keywords: Band-gap engineering; giant Stark effect; transition-metal dichalcogenides; two-dimensional semiconductors

Subject Areas: Materials, Physics

Instruments: I05-ARPES

Other Facilities: Advanced Light Source

Added On: 06/02/2017 09:31

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