Atomic Defects and Doping of Monolayer NbSe2
Lan Nguyen,† Hannu-Pekka Komsa,‡ Ekaterina Khestanova,§ Reza J. Kashtiban,∥ Jonathan J. P. Peters,∥ Sean Lawlor,† Ana M. Sanchez,∥ Jeremy Sloan,∥ Roman V. Gorbachev,§ Irina V. Grigorieva,§ Arkady V. Krasheninnikov,⊥,#,¶ and Sarah J. Haigh*,† †
School of Materials and §School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom ‡ COMP Centre of Excellence, Department of Applied Physics, and ¶Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Finland ∥ Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom ⊥ Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany # National University of Science and Technology MISiS, Leninskiy Prospekt, Moscow, 119049, Russian Federation S Supporting Information *
ABSTRACT: We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material. KEYWORDS: air-sensitive 2D crystals, graphene encapsulation, monolayer NbSe2, transition metal dichalcogenides, atomic resolution TEM, defect dynamics, Pt doping
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2D crystals via substitutional doping is a promising research area.5,10,12,13,16,17 Niobium diselenide (NbSe2) is a 2D crystal that is gathering much attention; it demonstrates superconductivity at low temperatures (
