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      Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures

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          Abstract

          Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS 2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS 2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS 2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS 2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A 1g peak of MoS 2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS 2 as a result of charge transfer from MoS 2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.

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          Most cited references39

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          Emerging photoluminescence in monolayer MoS2.

          Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS(2), a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS(2) crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d-electron system. This observation shows that quantum confinement in layered d-electron materials like MoS(2) provides new opportunities for engineering the electronic structure of matter at the nanoscale.
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            Graphene: Status and Prospects

            A. K. Geim (2010)
            Graphene is a wonder material with many superlatives to its name. It is the thinnest material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have the smallest effective mass (it is zero) and can travel micrometer-long distances without scattering at room temperature. Graphene can sustain current densities 6 orders higher than copper, shows record thermal conductivity and stiffness, is impermeable to gases and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a bench-top experiment. What are other surprises that graphene keeps in store for us? This review analyses recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
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              Atomically thin MoS2: A new direct-gap semiconductor

              The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N = 1, 2, ... 6 S-Mo-S monolayers have been investigated by optical spectroscopy. Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure. With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 0.6 eV. This leads to a crossover to a direct-gap material in the limit of the single monolayer. Unlike the bulk material, the MoS2 monolayer emits light strongly. The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of 1000 compared with the bulk material.
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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                01 June 2016
                2016
                : 6
                : 26656
                Affiliations
                [1 ]Laboratoire de Photonique et de Nanostructures (CNRS- LPN), Route de Nozay , 91460 Marcoussis, France
                [2 ]Department of Physics and Astronomy, University of Pennsylvania , 209S 33rd Street, Philadelphia, Pennsylvania 19104, USA
                [3 ]Institut des Nanosciences de Paris, UPMC, 4 place Jussieu , boîte courrier 840, 75252 Paris cedex 05, France
                [4 ]Laboratoire d’Innovation en Chimie des Surfaces et Nanosciences, DSM/NIMBE/LICSEN (CNRS UMR 3685), CEA Saclay , 91191 Gif-sur-Yvette Cedex, France
                [5 ]Synchrotron-SOLEIL, Saint-Aubin , BP48, F91192 Gif sur Yvette Cedex, France
                [6 ]SPEC, CEA, CNRS, Universite Paris-Saclay, CEA Saclay , 91191 Gif-sur-Yvette Cedex, France
                Author notes
                [*]

                These authors contributed equally to this work.

                Article
                srep26656
                10.1038/srep26656
                4894673
                27246929
                a9aa14ef-6dfc-4dee-a2c4-e6c828aba6c1
                Copyright © 2016, Macmillan Publishers Limited

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 15 January 2016
                : 03 May 2016
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