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Title: Origin of indirect optical transitions in few-layer MoS2, WS2, and WSe2
Authors: Zhao, W.
Ribeiro, R.M.
Toh, M.
Carvalho, A.
Kloc, C.
Castro Neto, A.H. 
Eda, G. 
Keywords: exciton
indirect band gap
photoluminescence spectroscopy
thermal expansion
Transition metal dichalcogenides
Issue Date: 13-Nov-2013
Citation: Zhao, W., Ribeiro, R.M., Toh, M., Carvalho, A., Kloc, C., Castro Neto, A.H., Eda, G. (2013-11-13). Origin of indirect optical transitions in few-layer MoS2, WS2, and WSe2. Nano Letters 13 (11) : 5627-5634. ScholarBank@NUS Repository.
Abstract: It has been well-established that single layer MX2 (M = Mo, W and X = S, Se) are direct gap semiconductors with band edges coinciding at the K point in contrast to their indirect gap multilayer counterparts. In few-layer MX2, there are two valleys along the Γ-K line with similar energy. There is little understanding on which of the two valleys forms the conduction band minimum (CBM) in this thickness regime. We investigate the conduction band valley structure in few-layer MX2 by examining the temperature-dependent shift of indirect exciton photoluminescence peak. Highly anisotropic thermal expansion of the lattice and the corresponding evolution of the band structure result in a distinct peak shift for indirect transitions involving the K and Λ (midpoint along Γ-K) valleys. We identify the origin of the indirect emission and concurrently determine the relative energy of these valleys. © 2013 American Chemical Society.
Source Title: Nano Letters
ISSN: 15306984
DOI: 10.1021/nl403270k
Appears in Collections:Staff Publications

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