title: Layer-by-layer thinning of MoS2 by plasma.
abstract: The electronic structures of two-dimensional materials are strongly dependent on their thicknesses; for example, there is an indirect to direct band gap transition from multilayer to single-layer MoS2. A simple, efficient, and nondestructive way to control the thickness of MoS2 is highly desirable for the study of thickness-dependent properties as well as for applications. Here, we present layer-by-layer thinning of MoS2 nanosheets down to monolayer by using Ar(+) plasma. Atomic force microscopy, high-resolution transmission electron microscopy, optical contrast, Raman, and photoluminescence spectra suggest that the top layer MoS2 is totally removed by plasma while the bottom layer remains almost unaffected. The evolution of Raman and photoluminescence spectra of MoS2 with thickness change is also investigated. Finally, we demonstrate that this method can be used to prepare two-dimensional heterostructures with periodical single-layer and bilayer MoS2. The plasma thinning of MoS2 is very reliable (with almost 100% success rate), can be easily scaled up, and is compatible with standard semiconductor process to generate heterostructures/patterns at nanometer scale, which may bring out interesting properties and new physics.
authors.affiliation: Department of Physics, Southeast University, SEU Research Center of Converging Technology, Nanjing 211189, China.
authors.forename: Yulu
authors.initials: Y
authors.lastname: Liu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Nan
authors.forename: Xing
authors.initials: X
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
authors.forename: Wenhui
authors.initials: W
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Bai
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhao
authors.forename: Litao
authors.initials: L
authors.lastname: Sun
authors.forename: Xinran
authors.initials: X
authors.lastname: Wang
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Ni
mesh_terms: D001128:Argon / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D008968:Molecular Conformation; D008982:Molybdenum / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D058626:Plasma Gases / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D004220:Disulfides; D058626:Plasma Gases; D001128:Argon; D008982:Molybdenum; C082964:molybdenum disulfide