New First Order Raman-active Modes in Few Layered Transition Metal Dichalcogenides
Terrones, Humberto (Pennsylvania State University)
Del Corro, Elena (Universidade Federal de Minas Gerais)
Feng, Sha (Pennsylvania State University)
Poumirol, Jean-Marie (Florida State University)
Rhodes, Daniel (Florida State University)
Smirnov, Dmitry (Florida State University)
Pradhan, Nihar R. (Florida State University)
Lin, Z Li (Pennsylvania State University)
Nguyen, Minh An T (Pennsylvania State University)
Elias, Ana Laura (Pennsylvania State University)
Mallouk, Thomas E. (Pennsylvania State University)
Balicas, Luis Molinuevo (Florida State University)
Pimenta, Marcos A. (Universidade Federal de Minas Gerais)
Terrones, Mauricio (Shinshu University)

Data:	2014
Resum:	Although the main Raman features of semiconducting transition metal dichalcogenides are well known for the monolayer and bulk, there are important differences exhibited by few layered systems which have not been fully addressed. WSe samples were synthesized and ab-initio calculations carried out. We calculated phonon dispersions and Raman-active modes in layered systems: WSe, MoSe, WS and MoS ranging from monolayers to five-layers and the bulk. First, we confirmed that as the number of layers increase, the E', E″ and E modes shift to lower frequencies, and the A' and A modes shift to higher frequencies. Second, new high frequency first order A' and A modes appear, explaining recently reported experimental data for WSe, MoSe and MoS. Third, splitting of modes around A' and A is found which explains those observed in MoSe. Finally, exterior and interior layers possess different vibrational frequencies. Therefore, it is now possible to precisely identify few-layered STMD.
Nota:	This work was supported by the U.S. Army Research Office MURI grant W911NF-11-1-0362, by the Materials Simulation Center of the Materials Research Institute (Penn State), the Research Computing and Cyberinfrastructure unit of Information Technology Services and Penn-State Center for Nanoscale Science. M.T. also acknowledges support from the Penn State Center for Nanoscale Science for seed grant on 2-D Layered Materials (DMR-0820404). The authors also acknowledge the Center for 2-Dimensional and Layered Materials at the Pennsylvania State University. M.A.P. and E.D.C. acknowledge the support of INCT Nanocarbono and the Brazilian agencies FAPEMIG and CNPq.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Scientific reports, Vol. 4 (February 2014) , art. 4215, ISSN 2045-2322

DOI: 10.1038/srep04215
PMID: 24572993

9 p, 1.9 MB

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