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New insights in the lattice dynamics of monolayers, bilayers, and trilayers of WSe2 and unambiguous determination of few-layer-flakes' thickness

De Luca, Marta and Cartoixà, Xavier and Martín-Sánchez, Javier and López-Suárez, Miquel and Trotta, Rinaldo and Rurali, Riccardo and Zardo, Ilaria. (2020) New insights in the lattice dynamics of monolayers, bilayers, and trilayers of WSe2 and unambiguous determination of few-layer-flakes' thickness. 2D Materials, 7 (2). 025004.

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Official URL: https://edoc.unibas.ch/75305/

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Abstract

Among the most common few-layers transition metal dichalcogenides (TMDs), WSe 2 is the most challenging material from the lattice dynamics point of view. Indeed, for a long time the main two phonon modes ( A 1g and ) have been wrongly assigned. In the last few years, these two modes have been properly interpreted, and their quasi-degeneracy in the monolayer has been used for its identification. In this work, we show that this approach has a limited validity and we propose an alternative, more general approach, based on multi-phonon bands. Moreover, we show and interpret all the peaks (about 40) appearing in the Raman spectra of monolayers, bilayers, and trilayers of WSe 2 by combining experimental wavelength- and polarization-dependent Raman studies with density-functional theory calculations providing the phonon dispersions, the polarization-resolved first-order Raman spectra, and the two-phonon density of states. This complete study not only offers a method to distinguish between monolayers, bilayers, and trilayers with no need of optical images and atomic force microscopy, but it also sheds light on the interpretation of single and multi-phonon bands appearing in the inelastic light scattering experiments of layered WSe 2 ; some of these bands were never observed before, and some were observed and uncertainly assigned. We promote the full understanding of the lattice dynamics of this material that is crucial for the realization of optoelectronics devices and of novel phononic metamaterials, such as TMDs superlattices.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Experimental Material Physics (Zardo)
UniBasel Contributors:Zardo, Ilaria and De Luca, Marta
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:IOP Publishing
ISSN:2053-1583
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Language:English
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Last Modified:06 Jan 2021 04:11
Deposited On:25 Mar 2020 09:16

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