Berlin 2024 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 2: 2D Materials and their Heterostructures I: hBN, WSe2, MoS2

DS 2.7: Vortrag

Montag, 18. März 2024, 11:15–11:30, A 060

DFT-assisted Investigation of Defects in 2D WSe2 by High-Resolution STEM and Differential Phase Contrast Imaging — •Maja Groll, Julius Bürger, Ioannis Caltzidis, Klaus D. Jöns, Wolf Gero Schmidt, Uwe Gerstmann, and Jörg K. N. Lindner — Department of Physics, Paderborn University, Germany

2D transition metal dichalcogenides and defects therein are currently the subject of intensive research due to their extraordinary optoelectronic properties. In particular, defects in monolayers, typically of vacancy type, are attracting much attention. Most spectroscopic investigations of material properties caused by defects are limited by the spatial resolution far above the atomic level. However, knowledge of the atomic structure is crucial for a detailed understanding of these properties. Modern scanning transmission electron microscopy (STEM) in combination with differential phase contrast imaging (DPC) allows for a structural analysis combined with the investigation of the electric field distribution at sub-atomic resolution. This enables the identification of defects and the resulting change in the field distribution. However, interpretation of STEM data is demanding because single substitutional atoms, such as oxygen, are difficult to detect and can nevertheless influence the physical and chemical properties. Here, vacancies in mechanically exfoliated 2D WSe2 flakes are analysed with focus on possible substitutional atoms. Conventional STEM at an acceleration voltage of 80keV in combination with STEM-DPC and density functional theory (DFT) calculations are used to characterize point defects and investigate their charge density distribution.

Keywords: TMDs; STEM; DPC; Electric field distribution; defects