Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets

Houk Jang, Krishna P. Dhakal, Kyung Il Joo, Won Seok Yun, Sachin M. Shinde, Xiang Chen, Soon Moon Jeong, Suk Woo Lee, Zonghoon Lee, Jae Dong Lee, Jong-Hyun Ahn, Hyunmin Kim

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Understanding the collaborative behaviors of the excitons and phonons that result from light–matter interactions is important for interpreting and optimizing the underlying fundamental physics at work in devices made from atomically thin materials. In this study, the generation of exciton-coupled phonon vibration from molybdenum disulfide (MoS2) nanosheets in a pre-excitonic resonance condition is reported. A strong rise-to-decay profile for the transient second-harmonic generation (TSHG) of the probe pulse is achieved by applying substantial (20%) beam polarization normal to the nanosheet plane, and tuning the wavelength of the pump beam to the absorption of the A-exciton. The time-dependent TSHG signals clearly exhibit acoustic phonon generation at vibration modes below 10 cm−1 (close to the Γ point) after the photoinduced energy is transferred from exciton to phonon in a nonradiative fashion. Interestingly, by observing the TSHG signal oscillation period from MoS2 samples of varying thicknesses, the speed of the supersonic waves generated in the out-of-plane direction (Mach 8.6) is generated. Additionally, TSHG microscopy reveals critical information about the phase and amplitude of the acoustic phonons from different edge chiralities (armchair and zigzag) of the MoS2 monolayers. This suggests that the technique could be used more broadly to study ultrafast physics and chemistry in low-dimensional materials and their hybrids with ultrahigh fidelity.

Original languageEnglish
Article number1705190
JournalAdvanced Materials
Volume30
Issue number14
DOIs
Publication statusPublished - 2018 Apr 5

Fingerprint

Nanosheets
Harmonic generation
Excitons
Imaging techniques
Phonons
Physics
Acoustics
Chirality
Mach number
Molybdenum
Vibrations (mechanical)
Monolayers
Microscopic examination
Tuning
Pumps
Polarization
Wavelength
LDS 751

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Jang, H., Dhakal, K. P., Joo, K. I., Yun, W. S., Shinde, S. M., Chen, X., ... Kim, H. (2018). Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets. Advanced Materials, 30(14), [1705190]. https://doi.org/10.1002/adma.201705190
Jang, Houk ; Dhakal, Krishna P. ; Joo, Kyung Il ; Yun, Won Seok ; Shinde, Sachin M. ; Chen, Xiang ; Jeong, Soon Moon ; Lee, Suk Woo ; Lee, Zonghoon ; Lee, Jae Dong ; Ahn, Jong-Hyun ; Kim, Hyunmin. / Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets. In: Advanced Materials. 2018 ; Vol. 30, No. 14.
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Jang, H, Dhakal, KP, Joo, KI, Yun, WS, Shinde, SM, Chen, X, Jeong, SM, Lee, SW, Lee, Z, Lee, JD, Ahn, J-H & Kim, H 2018, 'Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets', Advanced Materials, vol. 30, no. 14, 1705190. https://doi.org/10.1002/adma.201705190

Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets. / Jang, Houk; Dhakal, Krishna P.; Joo, Kyung Il; Yun, Won Seok; Shinde, Sachin M.; Chen, Xiang; Jeong, Soon Moon; Lee, Suk Woo; Lee, Zonghoon; Lee, Jae Dong; Ahn, Jong-Hyun; Kim, Hyunmin.

In: Advanced Materials, Vol. 30, No. 14, 1705190, 05.04.2018.

Research output: Contribution to journalArticle

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AU - Jang, Houk

AU - Dhakal, Krishna P.

AU - Joo, Kyung Il

AU - Yun, Won Seok

AU - Shinde, Sachin M.

AU - Chen, Xiang

AU - Jeong, Soon Moon

AU - Lee, Suk Woo

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AU - Lee, Jae Dong

AU - Ahn, Jong-Hyun

AU - Kim, Hyunmin

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AB - Understanding the collaborative behaviors of the excitons and phonons that result from light–matter interactions is important for interpreting and optimizing the underlying fundamental physics at work in devices made from atomically thin materials. In this study, the generation of exciton-coupled phonon vibration from molybdenum disulfide (MoS2) nanosheets in a pre-excitonic resonance condition is reported. A strong rise-to-decay profile for the transient second-harmonic generation (TSHG) of the probe pulse is achieved by applying substantial (20%) beam polarization normal to the nanosheet plane, and tuning the wavelength of the pump beam to the absorption of the A-exciton. The time-dependent TSHG signals clearly exhibit acoustic phonon generation at vibration modes below 10 cm−1 (close to the Γ point) after the photoinduced energy is transferred from exciton to phonon in a nonradiative fashion. Interestingly, by observing the TSHG signal oscillation period from MoS2 samples of varying thicknesses, the speed of the supersonic waves generated in the out-of-plane direction (Mach 8.6) is generated. Additionally, TSHG microscopy reveals critical information about the phase and amplitude of the acoustic phonons from different edge chiralities (armchair and zigzag) of the MoS2 monolayers. This suggests that the technique could be used more broadly to study ultrafast physics and chemistry in low-dimensional materials and their hybrids with ultrahigh fidelity.

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Jang H, Dhakal KP, Joo KI, Yun WS, Shinde SM, Chen X et al. Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets. Advanced Materials. 2018 Apr 5;30(14). 1705190. https://doi.org/10.1002/adma.201705190