title: Electronic structure of a quasi-freestanding MoS₂ monolayer.
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.
authors.affiliation: School of Physics, Suranaree University of Technology , Nakhon Ratchasima, 30000, Thailand.
authors.forename: T
authors.initials: T
authors.lastname: Eknapakul
authors.forename: P D C
authors.initials: PD
authors.lastname: King
authors.forename: M
authors.initials: M
authors.lastname: Asakawa
authors.forename: P
authors.initials: P
authors.lastname: Buaphet
authors.forename: R-H
authors.initials: RH
authors.lastname: He
authors.forename: S-K
authors.initials: SK
authors.lastname: Mo
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: K M
authors.initials: KM
authors.lastname: Shen
authors.forename: F
authors.initials: F
authors.lastname: Baumberger
authors.forename: T
authors.initials: T
authors.lastname: Sasagawa
authors.forename: S
authors.initials: S
authors.lastname: Jungthawan
authors.forename: W
authors.initials: W
authors.lastname: Meevasana