Regensburg 2022 – scientific programme

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DS: Fachverband Dünne Schichten

DS 17: 2D Materials 6 (joint session DS/CPP)

DS 17.7: Talk

Wednesday, September 7, 2022, 12:45–13:00, H17

Characterization of 2D WSe2 by high-resolution STEM and Differential Phase Contrast STEM — •Maja Groll¹, Julius Bürger¹, Ioannis Caltzidis², Marc Sartison², Klaus Jöns², and Jörg Lindner¹ — ¹Nanostructuring, Nanoanalysis and Photonic Materials Group, Department of Physics, Paderborn University, Germany — ²Hybrid Quantum Photonic Devices, Department of Physics, Paderborn University, Germany

2D transition metal dichalcogenides (TMDs) are gaining attention as their optical and electronic properties differ from those of their bulk counterparts. In particular, layer thickness-dependent properties, such as the transition from an indirect to a direct band gap in monolayers, make these materials interesting for photonic and optoelectronic applications. At the same time 2D-TMDs are ideal materials for the advancement of new techniques in scanning transmission electron microscopy (STEM) like differential phase contrast (DPC)-STEM. Using a spherical aberration corrected STEM, this technique enables the quantification of atomic electric fields with sub-atomic resolution if the specimen is sufficiently thin. In order to examine the atomic electric fields of TMDs, we transferred mechanically exfoliated mono- and multilayers of tungsten diselenide (WSe2) to TEM grids. The atomic structure of WSe2 flakes and their thickness are studied using TEM, energy filtered TEM and STEM. STEM-DPC measurements are performed using an eight-fold segmented bright-field STEM detector measuring the beam deflection due to the internal fields. Results are presented for WSe2 flakes of different thickness and compared with simulations.