@article{d6bfc3adcad9494a9c3bed8aee93d524,
title = "New First Order Raman-active Modes in Few Layered Transition Metal Dichalcogenides",
abstract = "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. WSe2 samples were synthesized and ab-initio calculations carried out. We calculated phonon dispersions and Raman-active modes in layered systems: WSe2, MoSe2, WS2 and MoS2 ranging from monolayers to five-layers and the bulk. First, we confirmed that as the number of layers increase, the E′, E″ and E2g modes shift to lower frequencies, and the A′1 and A1g modes shift to higher frequencies. Second, new high frequency first order A′1 and A1g modes appear, explaining recently reported experimental data for WSe2, MoSe2 and MoS2. Third, splitting of modes around A′1 and A1g is found which explains those observed in MoSe2. Finally, exterior and interior layers possess different vibrational frequencies. Therefore, it is now possible to precisely identify few-layered STMD.",
author = "H. Terrones and {Del Corro}, E. and S. Feng and Poumirol, {J. M.} and D. Rhodes and D. Smirnov and Pradhan, {N. R.} and Z. Lin and Nguyen, {M. A.T.} and El{\'i}as, {A. L.} and Mallouk, {T. E.} and L. Balicas and Pimenta, {M. A.} and M. Terrones",
note = "Funding Information: 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. Publisher Copyright: {\textcopyright} 2014, Nature Publishing Group. All rights reserved.",
year = "2014",
month = apr,
day = "1",
doi = "10.1038/srep04215",
language = "English (US)",
volume = "4",
journal = "Scientific Reports",
issn = "2045-2322",
publisher = "Nature Publishing Group",
}