New First Order Raman-active Modes in Few Layered Transition Metal Dichalcogenides

• DOI: 10.1038/srep04215
• Publication Date: 2014-02-27T10:21:12Z
• Authors: H. Terrones; E. Del Corro; S. Feng; J. M. Poumirol; D. Rhodes; D. Smirnov; N. R. Pradhan; Z. Lin; M. A. T. Nguyen; A. L. Elías; T. E. Mallouk; L. Balicas; M. A. Pimenta; M. Terrones
• Keywords: Frequency shift

Although the main Raman features of semiconducting transition metal dichalcogenides are well known for monolayer and bulk, there important differences exhibited by few layered systems which have not been fully addressed. WSe2 samples were synthesized ab-initio calculations carried out. We calculated phonon dispersions Raman-active modes in systems: WSe2, MoSe2, WS2 MoS2 ranging from monolayers to five-layers bulk. First, we confirmed that as number layers increase, E′, E″ E2g shift lower frequencies A′1 A1g higher frequencies. Second, new high frequency first order appear, explaining recently reported experimental data MoSe2 MoS2. Third, splitting around is found explains those observed MoSe2. Finally, exterior interior possess different vibrational Therefore, it now possible precisely identify few-layered STMD.