title: Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures.
abstract: Combining monolayers of different two-dimensional semiconductors into heterostructures creates new phenomena and device possibilities. Understanding and exploiting these phenomena hinge on knowing the electronic structure and the properties of interlayer excitations. We determine the key unknown parameters in MoSe2/WSe2heterobilayers by using rational device design and submicrometer angle-resolved photoemission spectroscopy (μ-ARPES) in combination with photoluminescence. We find that the bands in the K-point valleys are weakly hybridized, with a valence band offset of 300 meV, implying type II band alignment. We deduce that the binding energy of interlayer excitons is more than 200 meV, an order of magnitude higher than that in analogous GaAs structures. Hybridization strongly modifies the bands at Γ, but the valence band edge remains at the K points. We also find that the spectrum of a rotationally aligned heterobilayer reflects a mixture of commensurate and incommensurate domains. These results directly answer many outstanding questions about the electronic nature of MoSe2/WSe2heterobilayers and demonstrate a practical approach for high spectral resolution in ARPES of device-scale structures.
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Wilson
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Paul V
authors.identifier: 0000-0002-2935-5820
authors.initials: PV
authors.lastname: Nguyen
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Kyle
authors.initials: K
authors.lastname: Seyler
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Pasqual
authors.identifier: 0000-0002-5909-1686
authors.initials: P
authors.lastname: Rivera
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
authors.forename: Alexander J
authors.identifier: 0000-0002-3017-1754
authors.initials: AJ
authors.lastname: Marsden
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
authors.forename: Zachary P L
authors.initials: ZP
authors.lastname: Laker
authors.affiliation: Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
authors.forename: Gabriel C
authors.initials: GC
authors.lastname: Constantinescu
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, 34149 Trieste, Italy.; Physics Department, University of Trieste, Via Valerio 2, 34127 Trieste, Italy.
authors.forename: Viktor
authors.initials: V
authors.lastname: Kandyba
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, 34149 Trieste, Italy.
authors.forename: Alexei
authors.identifier: 0000-0003-4125-3779
authors.initials: A
authors.lastname: Barinov
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
authors.forename: Nicholas D M
authors.identifier: 0000-0001-5613-3679
authors.initials: ND
authors.lastname: Hine
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.; Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Physics, University of Washington, Seattle, WA 98195, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Cobden
keywords: 2D semiconductor; Graphene; band hybridization; commensuration; electronic properties; heterobilayer; linear-scaling DFT; photoluminescence; μ-ARPES