Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 35: 2D Materials I: Growth and Properties of Transition Metal Dichalcogenides, Phase Transitions
O 35.9: Vortrag
Dienstag, 2. April 2019, 16:00–16:15, H14
Damage mechanisms in two-dimensional MoS2 under electron irradiation — •Silvan Kretschmer1 and Arkady Krasheninnikov1,2 — 1Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany — 2Department of Applied Physics, Aalto University School of Science, Aalto, Finland
Two-dimensional (2D) materials are routinely characterized nowadays in the transmission electron microscope (TEM). The high-energy electron beam in TEM can create defects in the target, and as the influence of defects on materials properties is expected to be stronger in systems with reduced dimensionalities, understanding defect production in 2D materials is of particular importance. Irradiation-induced defects can appear through three mechanisms, namely ballistic or knock-on damage (1), ionization and electronic excitations (2) and beam-induced chemical etching (3). Only the first channel is well understood, while observations of defects formation in 2D transition metal dichalcogenides below the knock-on threshold points out that other mechanism should be important. Here we investigate the role of electronic excitations in defect production by using advanced first-principles simulation techniques based on the Ehrenfest dynamics combined with time-dependent density-functional theory and demonstrate that a combination of excitations and knock-on damage in 2D MoS2 under electron beam can give rise to the formation of vacancies and explain the experimental observations.