title: Atomic Defects and Doping of Monolayer NbSe2.
abstract: We have investigated the structure of atomic defects within monolayer NbSe2encapsulated 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 NbSe2lattice 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.
authors.forename: Lan
authors.initials: L
authors.lastname: Nguyen
authors.forename: Hannu-Pekka
authors.initials: HP
authors.lastname: Komsa
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Khestanova
authors.affiliation: Department of Physics, University of Warwick , Coventry, CV4 7AL, United Kingdom.
authors.forename: Reza J
authors.initials: RJ
authors.lastname: Kashtiban
authors.affiliation: Department of Physics, University of Warwick , Coventry, CV4 7AL, United Kingdom.
authors.forename: Jonathan J P
authors.initials: JJ
authors.lastname: Peters
authors.forename: Sean
authors.initials: S
authors.lastname: Lawlor
authors.affiliation: Department of Physics, University of Warwick , Coventry, CV4 7AL, United Kingdom.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Sanchez
authors.affiliation: Department of Physics, University of Warwick , Coventry, CV4 7AL, United Kingdom.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sloan
authors.forename: Roman V
authors.initials: RV
authors.lastname: Gorbachev
authors.forename: Irina V
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: 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.
authors.forename: Arkady V
authors.identifier: 0000-0003-0074-7588
authors.initials: AV
authors.lastname: Krasheninnikov
authors.forename: Sarah J
authors.identifier: 0000-0001-5509-6706
authors.initials: SJ
authors.lastname: Haigh
keywords: Pt doping; air-sensitive 2D crystals; atomic resolution TEM; defect dynamics; graphene encapsulation; monolayer NbSe2; transition metal dichalcogenides