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Atomic Structure and Spectroscopy of Single Metal (Cr, V) Substitutional Dopants in Monolayer MoS 2

DOI: 10.1021/acsnano.6b05674 DOI Help

Authors: Alex W. Robertson (University of Oxford) , Yung-chang Lin (National Institute of Advanced Industrial Science and Technology (AIST)) , Shanshan Wang (University of Oxford) , Hidetaka Sawada (University of Oxford; JEOL Limited; Diamond Light Source) , Christopher S. Allen (University of Oxford; Diamond Light Source) , Qu Chen (University of Oxford) , Sungwoo Lee (Seoul National University) , Gun-do Lee (Seoul National University) , Joohee Lee (Seoul National University) , Seungwu Han (Seoul National University) , Euijoon Yoon (Seoul National University) , Angus I. Kirkland (University of Oxford) , Heeyeon Kim (Korea Institute of Energy Research) , Kazu Suenaga (National Institute of Advanced Industrial Science and Technology (AIST)) , Jamie H. Warner (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Nano , VOL 10 , PAGES 10227 - 10236

State: Published (Approved)
Published: November 2016

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 MoS2 monolayer 2D crystals as single atom substitutional dopants in place of Mo. We attribute these impurities to trace elements present in the MoO3 CVD 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 MoS2 monolayers 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 MoS2 material. These transferred impurities could help explain the presence of trapped charges in CVD prepared MoS2.

Journal Keywords: defects; dopants; EELS; electron microscopy; MoS2; STEM; TEM

Subject Areas: Materials, Physics

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E02-JEM ARM 300CF