Interlayer Breathing and Shear Modes in Few-Trilayer MoS2 and WSe2
- 24 February 2013
- journal article
- research article
- Published by American Chemical Society (ACS) in Nano Letters
- Vol. 13 (3), 1007-1015
- https://doi.org/10.1021/nl304169w
Abstract
Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently attracted tremendous interest as potential valleytronic and nanoelectronic materials, in addition to being well-known as excellent lubricants in the bulk. The interlayer van der Waals (vdW) coupling and low-frequency phonon modes and how they evolve with the number of layers are important for both the mechanical and the electrical properties of 2D TMDs. Here we uncover the ultralow frequency interlayer breathing and shear modes in few-layer MoS2 and WSe2, prototypical layered TMDs, using both Raman spectroscopy and first principles calculations. Remarkably, the frequencies of these modes can be perfectly described using a simple linear chain model with only nearest-neighbor interactions. We show that the derived in-plane (shear) and out-of-plane (breathing) force constants from experiment remain the same from two-layer 2D crystals to the bulk materials, suggesting that the nanoscale interlayer frictional characteristics of these excellent lubricants should be independent of the number of layers.Keywords
This publication has 39 references indexed in Scilit:
- Control of valley polarization in monolayer MoS2 by optical helicityNature Nanotechnology, 2012
- Coupled Spin and Valley Physics in Monolayers ofand Other Group-VI DichalcogenidesPhysical Review Letters, 2012
- Synthesis of Large‐Area MoS2 Atomic Layers with Chemical Vapor DepositionAdvanced Materials, 2012
- Valley-selective circular dichroism of monolayer molybdenum disulphideNature Communications, 2012
- Photoluminescence from Chemically Exfoliated MoS2Nano Letters, 2011
- Single-Layer Semiconducting Nanosheets: High-Yield Preparation and Device FabricationAngewandte Chemie-International Edition, 2010
- Atomically Thin: A New Direct-Gap SemiconductorPhysical Review Letters, 2010
- Valley-dependent optoelectronics from inversion symmetry breakingPhysical Review B, 2008
- Two-dimensional atomic crystalsProceedings of the National Academy of Sciences of the United States of America, 2005
- The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural propertiesAdvances in Physics, 1969