Journal
ACS NANO
Volume 5, Issue 7, Pages 5903-5908Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn201698t
Keywords
two-dimensional materials; transition metal dichalcogenides; density functional theory; EELS; plasmon
Categories
Funding
- Army Research Office [W911NF-11-1-0171]
- TeraGrid [TG-PHY100022, TG-DMR090098]
- Center for Computation and Visualization at Brown University
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Since discovery of graphene, layered materials have drawn considerable attention because of their possible exfoliation into single and multilayer 2D sheets. Because of strong surface effects, the properties of these materials vary drastically with the number of layers in a sheet. We have performed first-principles density functional based calculations to evaluate the electron energy loss spectrum (EELS) of bulk, monolayer, and bilayer configurations of several transition metal dichalcogenides, which include semiconducting as well as metallic compounds. Our investigation shows that the peaks in the EELS spectra move toward larger wavelengths (red shift) with the decrease In number of layers. The pi plasmon peak shifts slightly by 0.5-1.0 eV, while a significant shift of around 5.5-13.0 eV is obtained for pi + sigma plasmon, when exfoliated from bulk to single. layer. This underscores the Importance of the interlayer coupling on the loss spectra and the dielectric properties. Our results are found to be in very good agreement with the recent measurements performed by Coleman et al. (Science 2011, 331, 568).
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