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

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.

Automated summary

In this study, the signature of mono- and few-layer MoS2 and MoTe2 was systematically evaluated using TEM methods. The number of layers was determined by comparing the results of three TEM methods and discussing their strengths and limitations.