Dresden 2020 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 12: 2D Materials I: Electronic Structure, Excitations, etc. (joint session O/CPP/HL)

HL 12.9: Vortrag

Montag, 16. März 2020, 12:45–13:00, WIL C107

Understanding electron beam damage in 2D materials from first-principles calculations: Effects of chemical etching and electronic excitation — •Silvan Kretschmer¹ and Arkady V. Krasheninnikov^1,2 — 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 dimensionality, 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 point out that other mechanism should be important. Here we investigate the role of beam-induced chemical etching and electronic excitations in defect production by using ab-initio molecular dynamic simulations and advanced first-principles simulation techniques based on the Ehrenfest dynamics combined with time-dependent density-functional theory. We demonstrate that the adsorption of small beam-induced radicals and electronic excitations dramatically lower the displacement threshold.