Electronic Structure of a Quasi-Freestanding MoS<sub>2</sub> Monolayer

Eknapakul, T.; King, P. D. C.; Asakawa, M.; Buaphet, P.; He, R.-H.; Mo, S.-K.; Takagi, H.; Shen, K. M.; Baumberger, Félix; Sasagawa, T.; Jungthawan, S.; Meevasana, W.

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Title		Electronic Structure of a Quasi-Freestanding MoS₂ Monolayer
Authors		Eknapakul, T. King, P. D. C. Asakawa, M. Buaphet, P. He, R.-H. Mo, S.-K. Takagi, H. Shen, K. M. Baumberger, Félix Sasagawa, T. Jungthawan, S. Meevasana, W. show all authors [1 - 12]
Published in		Nano Letters. 2014, vol. 14, no. 3, p. 1312-1316
Abstract		Several transition-metal dichalcogenides exhibit a striking crossover from indirect to direct band gap semiconductors as they are thinned down to a single monolayer. Here, we demonstrate how an electronic structure characteristic of the isolated monolayer can be created at the surface of a bulk MoS2 crystal. This is achieved by intercalating potassium in the interlayer van der Waals gap, expanding its size while simultaneously doping electrons into the conduction band. Our angle-resolved photoemission measurements reveal resulting electron pockets centered at the K̅ and K′ points of the Brillouin zone, providing the first momentum-resolved measurements of how the conduction band dispersions evolve to yield an approximately direct band gap of ∼1.8 eV in quasi-freestanding monolayer MoS2. As well as validating previous theoretical proposals, this establishes a novel methodology for manipulating electronic structure in transition-metal dichalcogenides, opening a new route for the generation of large-area quasi-freestanding monolayers for future fundamental study and use in practical applications.
Keywords		Molybdenum disulfide (MoS2) — Transition metal dichalcogenides (TMD) — Layered semiconductor — Electronic structure — Angle-resolved photoemission — Van der Waals expansion
Identifiers		DOI: 10.1021/nl4042824
Full text		Article (Published version) (3.1 MB) - Limited access to UNIGE Other version: http://pubs.acs.org/doi/abs/10.1021/nl4042824
Structures		Faculté des sciences / Section de physique / Département de physique de la matière quantique
Citation (ISO format)		EKNAPAKUL, T. et al. Electronic Structure of a Quasi-Freestanding MoS₂ Monolayer. In: Nano Letters, 2014, vol. 14, n° 3, p. 1312-1316. https://archive-ouverte.unige.ch/unige:42082