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Inter-Layer Coupling Induced Valence Band Edge Shift in Mono-to Few-Layer MoS2

TitleInter-Layer Coupling Induced Valence Band Edge Shift in Mono-to Few-Layer MoS2
Publication TypeJournal Article
Year of Publication2017
AuthorsTrainer, Daniel J., Putilov Aleksei V., Di Giorgio Cinzia, Saari Timo, Wang BaoKai, Wolak Mattheus, Chandrasena Ravini U., Lane Christopher, Chang Tay-Rong, Jeng Horng-Tay, Lin Hsin, Kronast Florian, Gray Alexander X., Xi Xiaoxing X., Nieminen Jouko, Bansil Arun, and Iavarone Maria
JournalSci Rep
Date Published01/2017
Keywordsatomic layers, chemical-vapor-deposition, films, graphene, molybdenum-disulfide, monolayer mos2, scanning tunneling microscope, states, transition-metal dichalcogenides, Transport

Recent progress in the synthesis of monolayer MoS2, a two-dimensional direct band-gap semiconductor, is paving new pathways toward atomically thin electronics. Despite the large amount of literature, fundamental gaps remain in understanding electronic properties at the nanoscale. Here, we report a study of highly crystalline islands of MoS2 grown via a refined chemical vapor deposition synthesis technique. Using high resolution scanning tunneling microscopy and spectroscopy (STM/STS), photoemission electron microscopy/spectroscopy (PEEM) and mu-ARPES we investigate the electronic properties of MoS2 as a function of the number of layers at the nanoscale and show in-depth how the band gap is affected by a shift of the valence band edge as a function of the layer number. Green's function based electronic structure calculations were carried out in order to shed light on the mechanism underlying the observed bandgap reduction with increasing thickness, and the role of the interfacial Sulphur atoms is clarified. Our study, which gives new insight into the variation of electronic properties of MoS2 films with thickness bears directly on junction properties of MoS2, and thus impacts electronics application of MoS2.


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