Exciton dynamics in suspended monolayer and few-layer MoS₂ 2D crystals.

By Hongyan Shi, R. Yan, Simone Bertolazzi, J. Brivio, B. Gao, Andras Kis, Debdeep Jena, Huili Grace Xing, Libai Huang. ACS Nano, 2013

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Femtosecond transient absorption spectroscopy and microscopy were employed to study exciton dynamics in suspended and Si₃N₄ substrate-supported monolayer and few-layer MoS₂ 2D crystals. Exciton dynamics for the monolayer and few-layer structures were found to be remarkably different from those of thick crystals when probed at energies near that of the lowest energy direct exciton (A exciton). The intraband relaxation rate was enhanced by more than 40 fold in the monolayer in comparison to that observed in the thick crystals, which we attributed to defect assisted scattering. Faster electron-hole recombination was found in monolayer and few-layer structures due to quantum confinement effects that lead to an indirect-direct band gap crossover. Nonradiative rather than radiative relaxation pathways dominate the dynamics in the monolayer and few-layer MoS₂. Fast trapping of excitons by surface trap states was observed in monolayer and few-layer structures, pointing to the importance of controlling surface properties in atomically thin crystals such as MoS₂ along with controlling their dimensions.

Subfields: Biomedical Engineering, Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/a39447762bc7004078c84a33b6a011c7783ddd88

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Citations in the corpus

Solution processed MoS2-PVA composite for sub-bandgap mode-locking of a wideband tunable ultrafast Er:fiber laser (2015, background): “MoS2 also displays ultrafast carrier dynamics [23, 25, 26], with a reported intraband relaxation time of ~30 fs [23] and carrier life-time of ~100 ps [26].”
Valley excitons in two-dimensional semiconductors (2015, background): “The observed time-resolved PL and absorption signals in monolayer TMDs exhibit multi-exponential decays [62,63,65,66], indicating complex exciton dynamics.”