title: Atomic Structure and Spectroscopy of Single Metal (Cr, V) Substitutional Dopants in Monolayer MoS2.
abstract: Dopants in two-dimensional dichalcogenides have a significant role in affecting electronic, mechanical, and interfacial properties. Controllable doping is desired for the intentional modification of such properties to enhance performance; however, unwanted defects and impurity dopants also have a detrimental impact, as often found for chemical vapor deposition (CVD) grown films. The reliable identification, and subsequent characterization, of dopants is therefore of significant importance. Here, we show that Cr and V impurity atoms are found in CVD grown MoS2monolayer 2D crystals as single atom substitutional dopants in place of Mo. We attribute these impurities to trace elements present in the MoO3CVD precursor. Simultaneous annular dark field scanning transmission electron microscopy (ADF-STEM) and electron energy loss spectroscopy (EELS) is used to map the location of metal atom substitutions of Cr and V in MoS2monolayers with single atom precision. The Cr and V are stable under electron irradiation at 60 to 80 kV, when incorporated into line defects, and when heated to elevated temperatures. The combined ADF-STEM and EELS differentiates these Cr and V dopants from other similar contrast defect structures, such as 2S self-interstitials at the Mo site, preventing misidentification. Density functional theory calculations reveal that the presence of Cr or V causes changes to the density of states, indicating doping of the MoS2material. These transferred impurities could help explain the presence of trapped charges in CVD prepared MoS2.
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Alex W
authors.initials: AW
authors.lastname: Robertson
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST) , AIST Central 5, Tsukuba 305-8564, Japan.
authors.forename: Yung-Chang
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.|JEOL Limited, 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.|Electron Physical Sciences Imaging Center, Diamond Light Source Limited, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Sawada
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.|Electron Physical Sciences Imaging Center, Diamond Light Source Limited, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Allen
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Qu
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Sungwoo
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Gun-Do
authors.initials: GD
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Joohee
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Seungwu
authors.initials: S
authors.lastname: Han
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Euijoon
authors.initials: E
authors.lastname: Yoon
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.|Electron Physical Sciences Imaging Center, Diamond Light Source Limited, Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: Angus I
authors.initials: AI
authors.lastname: Kirkland
authors.affiliation: Convergence Materials Laboratory, Korea Institute of Energy Research , 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Korea.
authors.forename: Heeyeon
authors.initials: H
authors.lastname: Kim
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST) , AIST Central 5, Tsukuba 305-8564, Japan.
authors.forename: Kazu
authors.initials: K
authors.lastname: Suenaga
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Jamie H
authors.initials: JH
authors.lastname: Warner
keywords: EELS; MoS2; STEM; TEM; defects; dopants; electron microscopy