Creation of single vacancies in hBN with electron irradiation

Abstract

Understanding electron irradiation effects is vital not only for reliable transmission electron microscopy characterization, but increasingly also for the controlled manipulation of two-dimensional materials. The displacement cross sections of monolayer hBN are measured using aberration-corrected scanning transmission electron microscopy in near ultra-high vacuum at primary beam energies between 50 and 90 keV. Damage rates below 80 keV are up to three orders of magnitude lower than previously measured at edges under poorer residual vacuum conditions where chemical etching appears to have been dominant. Notably, is possible to create single vacancies in hBN using electron irradiation, with boron almost twice as likely as nitrogen to be ejected below 80 keV. Moreover, any damage at such low energies cannot be explained by elastic knock-on, even when accounting for vibrations of the atoms. A theoretical description is developed to account for lowering of the displacement threshold due to valence ionization resulting from inelastic scattering of probe electrons, modelled using charge-constrained density functional theory molecular dynamics. Although significant reductions are found depending on the constrained charge, quantitative predictions for realistic ionization states are currently not possible. Nonetheless, there is potential for defect-engineering of hBN at the level of single vacancies using electron irradiation.

38 pages, 15 figures

References in corpus (6)

• Electric Field Effect in Atomically Thin Carbon Films
• Manipulating low-dimensional materials down to the level of single atoms with electron irradiation
• Towards atomically precise manipulation of 2D nanostructures in the electron microscope
• Isotope analysis in the transmission electron microscope
• Combined electronic excitation and knock-on damage in monolayer MoS2
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Cited by in corpus (4)

• Creation and Microscopic Origins of Single-Photon Emitters in Transition Metal Dichalcogenides and Hexagonal Boron Nitride
• Optimisation of electron irradiation for creating spin ensembles in hexagonal boron nitride
• Direct visualization of defect-controlled diffusion in van der Waals gaps
• Single photon emitters in hBN: Limitations of atomic resolution imaging and potential sources of error