Article (Scientific journals)
Unified Description of the Optical Phonon Modes in N-Layer MoTe2
Froehlicher, Guillaume; Lorchat, Etienne; Fernique, François et al.
2015In Nano Letters, 15, p. 6481–6489
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Keywords :
two-dimensional materials; layered crystals; transition metal dichalcogenides; Raman spectroscopy; interlayer breathing and shear modes; MoTe2; force constants; Davydov splitting; surface effects
Abstract :
[en] N-layer transition metal dichalcogenides provide a unique platform to investigate the evolution of the physical properties between the bulk (three-dimensional) and monolayer (quasi-two-dimensional) limits. Here, using high-resolution micro-Raman spectroscopy, we report a unified experimental description of the Γ-point optical phonons in N-layer 2H-molybdenum ditelluride (MoTe2). We observe series of N-dependent low-frequency interlayer shear and breathing modes (below 40 cm–1, denoted LSM and LBM) and well-defined Davydov splittings of the mid-frequency modes (in the range 100–200 cm–1, denoted iX and oX), which solely involve displacements of the chalcogen atoms. In contrast, the high-frequency modes (in the range 200–300 cm–1, denoted iMX and oMX), arising from displacements of both the metal and chalcogen atoms, exhibit considerably reduced splittings. The manifold of phonon modes associated with the in-plane and out-of-plane displacements are quantitatively described by a force constant model, including interactions up to the second nearest neighbor and surface effects as fitting parameters. The splittings for the iX and oX modes observed in N-layer crystals are directly correlated to the corresponding bulk Davydov splittings between the E2u/E1g and B1u/A1g modes, respectively, and provide a measurement of the frequencies of the bulk silent E2u and B1u optical phonon modes. Our analysis could readily be generalized to other layered crystals
Research center :
ULHPC - University of Luxembourg: High Performance Computing
Disciplines :
Physics
Author, co-author :
Froehlicher, Guillaume;  Université de Strasbourg and CNRS > UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg and NIE
Lorchat, Etienne;  Université de Strasbourg and CNRS > UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg and NIE
Fernique, François;  Université de Strasbourg and CNRS > UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg and NIE
Chaitanya, Joshi;  Indian Institute of Technology Bombay, India > Department of Physics
Molina-Sanchez, Alejandro ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Wirtz, Ludger ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Berciaud, Stephane;  Université de Strasbourg and CNRS > UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg and NIE
External co-authors :
yes
Language :
English
Title :
Unified Description of the Optical Phonon Modes in N-Layer MoTe2
Publication date :
September 2015
Journal title :
Nano Letters
ISSN :
1530-6992
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
15
Pages :
6481–6489
Peer reviewed :
Peer Reviewed verified by ORBi
FnR Project :
FNR7731521 - #4;modelling Of Carrier Dynamics And Ultra-fast Spectroscopy In Two-dimensional Materials, 2014 (01/12/2014-31/03/2017) - Alejandro Molina-sánchez
Funders :
FNR - Fonds National de la Recherche [LU]
University of Luxembourg - UL
Available on ORBilu :
since 24 November 2015

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