title: Exciton-dominated Dielectric Function of Atomically Thin MoS2 Films.
abstract: We systematically measure the dielectric function of atomically thin MoS2 films with different layer numbers and demonstrate that excitonic effects play a dominant role in the dielectric function when the films are less than 5-7 layers thick. The dielectric function shows an anomalous dependence on the layer number. It decreases with the layer number increasing when the films are less than 5-7 layers thick but turns to increase with the layer number for thicker films. We show that this is because the excitonic effect is very strong in the thin MoS2 films and its contribution to the dielectric function may dominate over the contribution of the band structure. We also extract the value of layer-dependent exciton binding energy and Bohr radius in the films by fitting the experimental results with an intuitive model. The dominance of excitonic effects is in stark contrast with what reported at conventional materials whose dielectric functions are usually dictated by band structures. The knowledge of the dielectric function may enable capabilities to engineer the light-matter interactions of atomically thin MoS2 films for the development of novel photonic devices, such as metamaterials, waveguides, light absorbers, and light emitters.
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Yiling
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Institute of High Performance Computing, A*STAR, Singapore 138632.
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA.|Department of Fiber and Polymer Science, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Alper
authors.initials: A
authors.lastname: Gurarslan
authors.affiliation: Materials Department, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Hartwin
authors.initials: H
authors.lastname: Peelaers
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Aspnes
authors.affiliation: Materials Department, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Chris G
authors.initials: CG
authors.lastname: Van de Walle
authors.affiliation: Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Nhan V
authors.initials: NV
authors.lastname: Nguyen
authors.affiliation: Institute of High Performance Computing, A*STAR, Singapore 138632.
authors.forename: Yong-Wei
authors.initials: YW
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA.|Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Linyou
authors.initials: L
authors.lastname: Cao