Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2.
By Weijie Zhao, Z. Ghorannevis, Kiran Kumar Amara, Jing. Pang, M. Toh, Xin Zhang, Christian Kloc, P. Tan, G. Eda. Nanoscale, 2013
844 citations recorded by the source corpus.
Thickness is one of the fundamental parameters that define the electronic, optical, and thermal properties of two-dimensional (2D) crystals. Phonons in molybdenum disulfide (MoS2) were recently found to exhibit unique thickness dependence due to the interplay between short and long range interactions. Here we report Raman spectra of atomically thin sheets of WS2 and WSe2, isoelectronic compounds of MoS2, in the mono- to few-layer thickness regime. We show that, similar to the case of MoS2, the characteristic A1g and E2g(1) modes exhibit stiffening and softening with increasing number of layers, respectively, with a small shift of less than 3 cm(-1) due to large mass of the atoms. Thickness dependence is also observed in a series of multiphonon bands arising from overtone, combination, and zone edge phonons, whose intensity exhibit significant enhancement in excitonic resonance conditions. Some of these multiphonon peaks are found to be absent only in monolayers. These features provide a unique fingerprint and rapid identification for monolayer flakes.
Subfields: Electrical and Electronic Engineering, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/727f33330fb0c4df14f000aa420d818cd6c95d3a
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Citations in the corpus
- Strain-induced direct–indirect bandgap transition and phonon modulation in monolayer WS2 (2015, background): “TMDs have long been known to possess a remarkable variety of important physical and chemical properties [3, 4].”
- Wafer-scale synthesis of monolayer WS2 for high-performance flexible photodetectors by enhanced chemical vapor deposition (2018, background): “8 cm–1 difference between the frequencies of the (1)2g E (Γ) and A1g(Γ) peaks, as well as the absence of the peak near 310 cm–1, point toward the presence of monolayer WS2 in the samples [30, 40].”
- Interlayer interactions in anisotropic atomically thin rhenium diselenide (2015, result): “The layer-numberdependent behavior of high frequency modes in WSe2 is similar with that in MoS2: The A1g and E2g modes blue-shift and red-shift from monolayer to bulk, respectively [47].”