Chinese Journal of Chemical Physics, Volume. 33, Issue 5, 547(2020)
Unveiling Defect-Mediated Carrier Dynamics in Few-Layer MoS2 Prepared by Ion Exchange Method via Ultrafast Vis-NIR-MIR Spectroscopy†
Fig. 1. (a) Absorption spectrum of MoS2 nanosheets on calcium fluoride window with A-, B-, and C-exciton features labeled. (b) Raman spectrum of MoS2 nanosheets showing two prominent modes as labeled. Open circles are the experimental points, and solid lines are the Gauss fits. (c) AFM image of MoS2 nanosheets; the inset is the height profile of the AFM image for three nanosheets.
Fig. 1. Temporal evolution of excitation-induced transmission change for the few-layer MoS2 nanosheets detected at 676 nm and 1026 nm, under the excitation of 676 nm (89μJ/cm2).
Fig. 2. Normalized temporal evolution of excitation-induced transmission change for the few-layer MoS2 detected at 676 nm, under the excitation of 676 nm with pump fluences of 38 and 89 μJ/cm2. The slow decay component that can last hundreds of picoseconds is strongly dependent on the pump fluence, which can be attributed to the thermalization of MoS2 lattice.
Fig. 2. Waiting time (
Fig. 3. (a) Temporal evolution of excitation-induced transmission change of few-layer MoS2 detected at 1026 nm, under the excitation of 676 nm with different pump fluences. Circles are data, and curves are bi-exponential fitting. (b) The excitation-induced peak amplitude (orange balls, left vertical axis) and the fitted time constants (red and green balls, right vertical axis) as the function of incident pump fluence
Fig. 3. (a) Transient absorption (TA) spectra at 0.6 ps time delay for the few-layer MoS2 after photoexcitation at 400 nm. The pump fluences are 110 μJ/cm2 for the visible probe and 50 μJ/cm2 for the NIR probe. (b) Temporal evolution of excitation-induced transmission change detected at 676 nm and 1026 nm under the excitation of 400 nm. Dots are data, and curves are multi-exponential fitting with the consideration of instrument response function (~150 fs).
Fig. 4. (a) A schematic illustration of photoinduced carrier relaxation processes in few-layer MoS2. The blue solid lines and green dotted line indicate the mid-gap states and Fermi level (
Fig. 4. Temporal evolution of excitation-induced transmission change for the few-layer MoS2 detected at 676 nm, under the excitation of 400 nm with different pump fluences.
Fig. 5. (a) Temporal evolution of excitation-induced transmission change for the few-layer MoS2 detected at 1026 nm, under the excitation of 400 nm with different pump fluences. Circles are data, and curves are multi-exponential fitting with the consideration of instrument response function (~150 fs).
Fig. 6. Results of global fitting analysis for the MIR TA data with three exponential decay functions showing (a) three exponential decay dynamics with time constants 0.7 ps, 3.1 ps and 10.2 ps, respectively, and (b) three corresponding decay associated difference spectra (DADS). The data was collected under the excitation of 676 nm with a pump fluence of 100 μJ/cm2.
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Zhen Chi, Hui-hui Chen, Zhuo Chen, Hai-long Chen. Unveiling Defect-Mediated Carrier Dynamics in Few-Layer MoS2 Prepared by Ion Exchange Method via Ultrafast Vis-NIR-MIR Spectroscopy†[J]. Chinese Journal of Chemical Physics, 2020, 33(5): 547
Received: Jul. 11, 2020
Accepted: Sep. 2, 2020
Published Online: Apr. 21, 2021
The Author Email: Chen Hai-long (hlchen@iphy.ac.cn)