title: Excitonic Effects in Tungsten Disulfide Monolayers on Two-Layer Graphene.
abstract: Light emission in atomically thin heterostructures is known to depend on the type of materials and the number and stacking sequence of the constituent layers. Here we show that the thickness of a two-dimensional substrate can be crucial in modulating the light emission. We study the layer-dependent charge transfer in vertical heterostructures built from monolayer tungsten disulfide (WS2) on one- and two-layer epitaxial graphene, unravelling the effect that the interlayer electronic coupling has on the excitonic properties of such heterostructures. We bring evidence that the excitonic properties of WS2 can be effectively tuned by the number of supporting graphene layers. Integrating WS2 monolayers with two-layer graphene leads to a significant enhancement of the photoluminescence response, up to 1 order of magnitude higher compared to WS2 supported on one-layer graphene. Our findings highlight the importance of substrate engineering when constructing atomically thin-layered heterostructures.
authors.affiliation: National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom.
authors.forename: Cristina E
authors.initials: CE
authors.lastname: Giusca
authors.affiliation: National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom.
authors.forename: Ivan
authors.initials: I
authors.lastname: Rungger
authors.affiliation: National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom.
authors.forename: Vishal
authors.initials: V
authors.lastname: Panchal
authors.affiliation: National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom.|Advanced Technology Institute, University of Surrey , Guildford GU2 7XH, United Kingdom.
authors.forename: Christos
authors.initials: C
authors.lastname: Melios
authors.forename: Zhong
authors.initials: Z
authors.lastname: Lin
authors.forename: Yu-Chuan
authors.initials: YC
authors.lastname: Lin
authors.forename: Ethan
authors.initials: E
authors.lastname: Kahn
authors.forename: Ana Laura
authors.initials: AL
authors.lastname: Elías
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Robinson
authors.forename: Mauricio
authors.initials: M
authors.lastname: Terrones
authors.affiliation: National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Kazakova
keywords: ab initio calculations; epitaxial graphene; excitonic effects; heterostructures; trions; tungsten disulfide monolayer; work function