Optical response of monolayer, few-layer and bulk tungsten disulfide
arXiv:1706.09285 · doi:10.1039/C7NR04672C
Abstract
We present a comprehensive optical study of thin films of tungsten disulfide (WS) with layer thicknesses ranging from mono- to octalayer and in the bulk limit. It is shown that the optical band-gap absorption of monolayer WS is governed by competing resonances arising from one neutral and two distinct negatively charged excitons whose contributions to the overall absorption of light vary as a function of temperature and carrier concentration. The photoluminescence response of monolayer WS is found to be largely dominated by disorder/impurity- and/or phonon-assisted recombination processes. The indirect band-gap luminescence in multilayer WS turns out to be a phonon-mediated process whose energy evolution with the number of layers surprisingly follows a simple model of a two-dimensional confinement. The energy position of the direct band-gap response (A and B resonances) is only weakly dependent on the layer thickness, which underlines an approximate compensation of the effect of the reduction of the exciton binding energy by the shrinkage of the apparent band gap. The A-exciton absorption-type spectra in multilayer WS display a non-trivial fine structure which results from the specific hybridization of the electronic states in the vicinity of the K-point of the Brillouin zone. The effects of temperature on the absorption-like and photoluminescence spectra of various WS layers are also quantified.
13 pages, 13 figures, electronic supporting information
References in corpus (19)
- Two Dimensional Atomic Crystals
- Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
- Light-emitting diodes by bandstructure engineering in van der Waals heterostructures
- Measurement of the optical dielectric function of transition metal dichalcogenide monolayers: MoS2, MoSe2, WS2 and WSe2
- Tightly bound excitons in monolayer WSe2
- Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
- k.p theory for two-dimensional transition metal dichalcogenide semiconductors
- Probing Excitonic Dark States in Single-layer Tungsten Disulfide
- Exciton Binding Energy of Monolayer WS2
- Electrical Control of Second-Harmonic Generation in a WSe2 Monolayer Transistor
- Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
- Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers
- Excitonic valley effects in monolayer WS under high magnetic fields
- Nonlinear valley and spin currents from Fermi pocket anisotropy in 2D crystals
- Three-particle Complexes in Two-Dimensional Semiconductors
- Ultra-low power threshold for laser induced changes in optical properties of 2D Molybdenum dichalcogenides
- Sub-bandgap voltage electroluminescence and magneto-oscillations in a WSe2 light-emitting van der Waals heterostructure
- Revealing the nature of excitons in liquid exfoliated monolayer WS2
- Observation of three-particle complexes in WS monolayers