Photoreflectance study of the near-band-edge transitions of chemical vapor deposition-grown mono- and few-layer MoS2 films

Kuang I. Lin, Yen Jen Chen, Bo Yan Wang, Yung Chen Cheng, Chang Hsiao Chen

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Room-temperature photoreflectance (PR) and reflectance (R) spectroscopy are utilized to investigate the near-band-edge transitions of molybdenum disulfide (MoS2) thin films grown on sapphire substrates by a hot-wall chemical vapor deposition system. The layer thickness and optical properties of the MoS2 thin films are confirmed by Raman spectroscopy, atomic force microscope, and photoluminescence (PL) analysis. The B exciton shows relatively weak PL intensity in comparing with the A exciton even for monolayer MoS2 films. In the R spectrum of few-layer MoS2, it is not possible to clearly observe exciton related features. The PR spectra have two sharp, derivative-like features on a featureless background. Throughout the PR lineshape fitting, the transition energies are designated as the A and B excitons at the K-point of the Brillouin zone, but at room temperature there seems to be no distinguishable feature corresponding to an H-point transition for the mono- and few-layer MoS2 films unlike in bulk. These transition energies are slightly larger than those obtained by PL, which is attributed to the Stokes shifts related to doping level. The obtained values of valence-band spin-orbit splitting are in good agreement with those from other experimental methods. By comparing the PR lineshapes, the dominant modulation mechanism is attributed to variations of the exciton transition energies due to change in the built-in electric field. On the strength of this study, PR spectroscopy is demonstrated as a powerful technique for characterizing the near-band-edge transitions of MoS2 from monolayer to bulk.

Original languageEnglish
Article number115703
JournalJournal of Applied Physics
Volume119
Issue number11
DOIs
Publication statusPublished - 2016 Mar 21

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excitons
vapor deposition
photoluminescence
molybdenum disulfides
room temperature
transition points
thin films
Brillouin zones
spectroscopy
energy
sapphire
Raman spectroscopy
microscopes
valence
orbits
reflectance
modulation
optical properties
electric fields
shift

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

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title = "Photoreflectance study of the near-band-edge transitions of chemical vapor deposition-grown mono- and few-layer MoS2 films",
abstract = "Room-temperature photoreflectance (PR) and reflectance (R) spectroscopy are utilized to investigate the near-band-edge transitions of molybdenum disulfide (MoS2) thin films grown on sapphire substrates by a hot-wall chemical vapor deposition system. The layer thickness and optical properties of the MoS2 thin films are confirmed by Raman spectroscopy, atomic force microscope, and photoluminescence (PL) analysis. The B exciton shows relatively weak PL intensity in comparing with the A exciton even for monolayer MoS2 films. In the R spectrum of few-layer MoS2, it is not possible to clearly observe exciton related features. The PR spectra have two sharp, derivative-like features on a featureless background. Throughout the PR lineshape fitting, the transition energies are designated as the A and B excitons at the K-point of the Brillouin zone, but at room temperature there seems to be no distinguishable feature corresponding to an H-point transition for the mono- and few-layer MoS2 films unlike in bulk. These transition energies are slightly larger than those obtained by PL, which is attributed to the Stokes shifts related to doping level. The obtained values of valence-band spin-orbit splitting are in good agreement with those from other experimental methods. By comparing the PR lineshapes, the dominant modulation mechanism is attributed to variations of the exciton transition energies due to change in the built-in electric field. On the strength of this study, PR spectroscopy is demonstrated as a powerful technique for characterizing the near-band-edge transitions of MoS2 from monolayer to bulk.",
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Photoreflectance study of the near-band-edge transitions of chemical vapor deposition-grown mono- and few-layer MoS2 films. / Lin, Kuang I.; Chen, Yen Jen; Wang, Bo Yan; Cheng, Yung Chen; Chen, Chang Hsiao.

In: Journal of Applied Physics, Vol. 119, No. 11, 115703, 21.03.2016.

Research output: Contribution to journalArticle

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AU - Lin, Kuang I.

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AB - Room-temperature photoreflectance (PR) and reflectance (R) spectroscopy are utilized to investigate the near-band-edge transitions of molybdenum disulfide (MoS2) thin films grown on sapphire substrates by a hot-wall chemical vapor deposition system. The layer thickness and optical properties of the MoS2 thin films are confirmed by Raman spectroscopy, atomic force microscope, and photoluminescence (PL) analysis. The B exciton shows relatively weak PL intensity in comparing with the A exciton even for monolayer MoS2 films. In the R spectrum of few-layer MoS2, it is not possible to clearly observe exciton related features. The PR spectra have two sharp, derivative-like features on a featureless background. Throughout the PR lineshape fitting, the transition energies are designated as the A and B excitons at the K-point of the Brillouin zone, but at room temperature there seems to be no distinguishable feature corresponding to an H-point transition for the mono- and few-layer MoS2 films unlike in bulk. These transition energies are slightly larger than those obtained by PL, which is attributed to the Stokes shifts related to doping level. The obtained values of valence-band spin-orbit splitting are in good agreement with those from other experimental methods. By comparing the PR lineshapes, the dominant modulation mechanism is attributed to variations of the exciton transition energies due to change in the built-in electric field. On the strength of this study, PR spectroscopy is demonstrated as a powerful technique for characterizing the near-band-edge transitions of MoS2 from monolayer to bulk.

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