Distinct photoluminescence and Raman spectroscopy signatures for identifying highly crystalline WS 2 monolayers produced
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Ayse Berkdemirb) Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA; and Nanotechnology Research Center and Kayseri Vocational College, Erciyes University, Kayseri 38039, Turkey
Junjie Wang Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Minh An Nguyen Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Ana Laura Elías, Néstor Perea-López, and Kazunori Fujisawa Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Bernd Kabius Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Victor Carozo Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
David A. Cullen Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Thomas E. Mallouk Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
J. Zhu Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Mauricio Terronesa),c) Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA; Department of Materials Science & Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA; and Research Center for Exotic Nanocarbons, Shinshu University, Nagano 380-8553, Japan (Received 24 September 2015; accepted 25 January 2016)
Transition metal dichalcogenides such as WS2 show exciting promise in electronic and optoelectronic applications. Significant variations in the transport, Raman, and photoluminescence (PL) can be found in the literature, yet it is rarely addressed why this is. In this report, Raman and PL of monolayered WS2 produced via different methods are studied and distinct features that indicate the degree of crystallinity of the material are observed. While the intensity of the LA(M) Raman mode is found to be a useful indicator to assess the crystallinity, PL is drastically more sensitive to the quality of the material than Raman spectroscopy. We also show that even exfoContributing Editor: Lain-Jong Li a) liated crystals, which are usually regarded as Address all correspondence to this author. the most pristine material, can contain large e-mail: [email protected] b) These authors contributed equally to this work. amounts of defects that would not be apparc) This author was an editor of this journal during the review and ent without Raman and PL measurements. decision stage. For
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