Exciton radiative lifetime in transition metal dichalcogenide monolayers
By C. Robert, D. Lagarde, F. Cadiz, Gang Wang, B. Lassagne, T. Amand, A. Balocchi, P. Renucci, S. Tongay, Bernhard Urbaszek and 1 more. 2016
362 citations recorded by the source corpus.
We have investigated the exciton dynamics in transition metal dichalcogenide monolayers using time-resolved photoluminescence experiments performed with optimized time resolution. For $\mathrm{MoS}{\mathrm{e}}_{2}$ monolayer, we measure ${\ensuremath{\tau}}_{\mathrm{rad}}^{0}=1.8\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.16em}{0ex}}\mathrm{ps}$ at $T=7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ that we interpret as the intrinsic radiative recombination time. Similar values are found for $\mathrm{WS}{\mathrm{e}}_{2}$ monolayers. Our detailed analysis suggests the following scenario: at low temperature $(T\ensuremath{\lesssim}50\phantom{\rule{0.16em}{0ex}}\mathrm{K})$, the exciton oscillator strength is so large that the entire light can be emitted before the time required for the establishment of a thermalized exciton distribution. For higher lattice temperatures, the photoluminescence dynamics is characterized by two regimes with very different characteristic times. First the photoluminescence intensity drops drastically with a decay time in the range of the picosecond driven by the escape of excitons from the radiative window due to exciton-phonon interactions. Following this first nonthermal regime, a thermalized exciton population is established gradually yielding longer photoluminescence decay times in the nanosecond range. Both the exciton effective radiative recombination and nonradiative recombination channels including exciton-exciton annihilation control the latter. Finally the temperature dependence of the measured exciton and trion dynamics indicates that the two populations are not in thermodynamical equilibrium.
Subfields: Electrical and Electronic Engineering, Materials Chemistry
View Paper: https://www.semanticscholar.org/paper/77cf9ca853d64d92f5912961f09efcd5db01bfbc
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Citations in the corpus
- Dark and bright exciton formation, thermalization, and photoluminescence in monolayer transition metal dichalcogenides (2017, background): “Exemplarily, the decay constant T1 was found to decrease as a function of temperature in MoSe2 in a recent study [47], which is the inverse behavior to the radiative lifetime shown in figure 5(a).”
- Valley-polarized exciton–polaritons in a monolayer semiconductor (2017, background): “Although the homogeneous exciton radiative lifetime is highly temperature dependent [44, 45], the total exciton decay time in MoS2 has been found to be nearly temperature independent τex = h̄/Γex = 4 ps [46, 47].”