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Title: Evolution of electronic structure in atomically thin sheets of ws 2 and wse2
Authors: Zhao, W.
Ghorannevis, Z.
Chu, L.
Toh, M.
Kloc, C.
Tan, P.-H.
Eda, G. 
Keywords: 2D crystals
Issue Date: 22-Jan-2013
Citation: Zhao, W., Ghorannevis, Z., Chu, L., Toh, M., Kloc, C., Tan, P.-H., Eda, G. (2013-01-22). Evolution of electronic structure in atomically thin sheets of ws 2 and wse2. ACS Nano 7 (1) : 791-797. ScholarBank@NUS Repository.
Abstract: Geometrical confinement effect in exfoliated sheets of layered materials leads to significant evolution of energy dispersion in mono- to few-layer thickness regime. Molybdenum disulfide (MoS2) was recently found to exhibit indirect-to-direct gap transition when the thickness is reduced to a single monolayer. Emerging photoluminescence (PL) from monolayer MoS2 opens up opportunities for a range of novel optoelectronic applications of the material. Here we report differential reflectance and PL spectra of mono- to few-layer WS2 and WSe2 that indicate that the band structure of these materials undergoes similar indirect-to-direct gap transition when thinned to a single monolayer. The transition is evidenced by distinctly enhanced PL peak centered at 630 and 750 nm in monolayer WS2 and WSe2, respectively. Few-layer flakes are found to exhibit comparatively strong indirect gap emission along with direct gap hot electron emission, suggesting high quality of synthetic crystals prepared by a chemical vapor transport method. Fine absorption and emission features and their thickness dependence suggest a strong effect of Se p-orbitals on the d electron band structure as well as interlayer coupling in WSe2. © 2012 American Chemical Society.
Source Title: ACS Nano
ISSN: 19360851
DOI: 10.1021/nn305275h
Appears in Collections:Staff Publications

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