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O: Fachverband Oberflächenphysik

O 79: 2D Materials V: Growth, Structure and Substrate Interaction

O 79.7: Talk

Thursday, March 21, 2024, 12:00–12:15, MA 005

Direct Beam-Induced Chemical Etching of 2D Materials in Transmission Electron Microscope — •Mitisha Jain, Silvan Kretschmer, and Arkady Krasheninnikov — Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany

The interaction of energetic electrons with the specimen during imaging in a transmission electron microscope (TEM) can give rise to the formation of defects or even complete destruction of the sample. This is particularly relevant to atomically thin two-dimensional (2D) materials. Depending on electron energy and material type, different mechanisms such as knock-on (ballistic) damage, inelastic interactions including ionization and excitations, as well as beam-mediated chemical etching can govern defect production. Using first-principles calculations combined with the McKinley-Feshbach formalism, we investigate the latter channel of damage creation in two representative 2D materials, MoS₂ and h-BN with adsorbed single adatoms (H, C, N, O, etc.), which can originate from molecules always present in the TEM column. We assess the ballistic displacement threshold energies T for the host atoms in 2D materials when adatoms are present and demonstrate that T can be reduced, as chemical bonds are locally weakened due to the formation of new bonds with the adatom. We conclude that while adatoms should play a role in damage creation in MoS₂, formation of defects in h-BN sheets at electron energies well below the knock-on threshold cannot be explained by the presence of adatoms, that is by the direct electron beam-induced chemical etching.

Keywords: Transmission electron microscope; hBN; MoS2; defects; 2D materials