Evaluation of TEM methods for their signature of the number of layers in mono- and few-layer TMDs as exemplified by MoS2 and MoTe2

Janis Köster; Alexander Storm; Tatiana E Gorelik; Michael J Mohn; Fabian Port; Manuel R Gonçalves; Ute Kaiser

doi:10.1016/j.micron.2022.103303

Evaluation of TEM methods for their signature of the number of layers in mono- and few-layer TMDs as exemplified by MoS₂ and MoTe₂

Micron. 2022 Sep:160:103303. doi: 10.1016/j.micron.2022.103303. Epub 2022 Jun 1.

Authors

Janis Köster¹, Alexander Storm¹, Tatiana E Gorelik¹, Michael J Mohn¹, Fabian Port², Manuel R Gonçalves², Ute Kaiser¹

Affiliations

¹ Electron Microscopy Group of Materials Science (EMMS), Central Facility for Electron Microscopy, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
² Institute of Experimental Physics, Ulm University, Ulm, Baden-Wuerttemberg, Germany.

PMID: 35709545
DOI: 10.1016/j.micron.2022.103303

Abstract

In mono- and few-layer 2D materials, the exact number of layers is a critical parameter, determining the materials' properties and thus their performance in future nano-devices. Here, we evaluate in a systematic manner the signature of exfoliated free-standing mono- and few-layer MoS₂ and MoTe₂ in TEM experiments such as high-resolution transmission electron microscopy, electron energy-loss spectroscopy, and 3D electron diffraction. A reference for the number of layers has been determined by optical contrast and AFM measurements on a substrate. Comparing the results, we discuss strengths and limitations, benchmarking the three TEM methods with respect to their ability to identify the exact number of layers.

Keywords: 2D materials; 3D electron diffraction (3D ED); Ab-initio calculations; HRTEM; MoS(2); MoTe(2); Momentum-resolved EELS (MR-EELS); Plasmon dispersion.