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arXiv · 1305.3880

Bandgap Engineering of Strained Monolayer and Bilayer MoS2

Hiram J. Conley·Bin Wang·Jed I. Ziegler·Richard F. Haglund Jr.·Sokrates T. Pantelides·Kirill I. Bolotin
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Abstract

We report the influence of uniaxial tensile mechanical strain in the range 0-2.2% on the phonon spectra and bandstructures of monolayer and bilayer molybdenum disulfide (MoS2) two-dimensional crystals. First, we employ Raman spectroscopy to observe phonon softening with increased strain, breaking the degeneracy in the E' Raman mode of MoS2, and extract a Grüneisen parameter of ~1.06. Second, using photoluminescence spectroscopy we measure a decrease in the optical band gap of MoS2 that is roughly linear with strain, ~45 meV% strain for monolayer MoS2 and ~120 meV% strain for bilayer MoS2. Third, we observe a pronounced strain-induced decrease in the photoluminescence intensity of monolayer MoS2 that is indicative of the direct-to-indirect transition of the character of the optical band gap of this material at applied strain of ~1.5%, a value supported by first-principles calculations that include excitonic effects. These observations constitute the first demonstration of strain engineering the band structure in the emergent class of two-dimensional crystals, transition-metal dichalcogenides.

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Hiram J. Conley, Bin Wang, Jed I. Ziegler, Richard F. Haglund Jr., Sokrates T. Pantelides, Kirill I. Bolotin. 2013-09-20. Bandgap Engineering of Strained Monolayer and Bilayer MoS2. https://doi.org/10.1021/nl4014748

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