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Low-Frequency Raman Fingerprints of Two-Dimensional Metal Dichalcogenide Layer Stacking Configurations

By Alexander A. Puretzky (1302459), Liangbo Liang (1395112), Xufan Li (1434421), Kai Xiao (421646), Kai Wang (21246), Masoud Mahjouri-Samani (1501996), Leonardo Basile (1544629), Juan Carlos Idrobo (1580023), Bobby G. Sumpter (537235), Vincent Meunier (1287186) and David B. Geohegan (1373514)

Abstract

The tunable optoelectronic properties of stacked two-dimensional (2D) crystal monolayers are determined by their stacking orientation, order, and atomic registry. Atomic-resolution Z-contrast scanning transmission electron microscopy (AR-Z-STEM) and electron energy loss spectroscopy (EELS) can be used to determine the exact atomic registration between different layers, in few-layer 2D stacks; however, fast optical characterization techniques are essential for rapid development of the field. Here, using two- and three-layer MoSe<sub>2</sub> and WSe<sub>2</sub> crystals synthesized by chemical vapor deposition, we show that the generally unexplored low frequency (LF) Raman modes (<50 cm<sup>–1</sup>) that originate from interlayer vibrations can serve as fingerprints to characterize not only the number of layers, but also their stacking configurations. <i>Ab initio</i> calculations and group theory analysis corroborate the experimental assignments determined by AR-Z-STEM and show that the calculated LF mode fingerprints are related to the 2D crystal symmetries

Topics: Biophysics, Medicine, Biotechnology, Developmental Biology, Chemical Sciences not elsewhere classified, Physical Sciences not elsewhere classified, Information Systems not elsewhere classified, electron energy loss spectroscopy, Raman, WSe 2 crystals, characterization techniques, LF mode fingerprints, EELS, chemical vapor deposition, 2 D crystal symmetries, crystal monolayers, interlayer vibrations, Ab initio calculations, group theory analysis
Year: 2015
DOI identifier: 10.1021/acsnano.5b01884.s001
OAI identifier: oai:figshare.com:article/2155984
Provided by: FigShare
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