Spatially resolved photoexcited charge-carrier dynamics in phase-engineered monolayer MoS2

Hisato Yamaguchi, Jean Christophe Blancon, Rajesh Kappera, Sidong Lei, Sina Najmaei, Benjamin D. Mangum, Gautam Gupta, Pulickel M. Ajayan, Jun Lou, Manish Chhowalla, Jared J. Crochet, Aditya D. Mohite

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)


A fundamental understanding of the intrinsic optoelectronic properties of atomically thin transition-metal dichalcogenides (TMDs) is crucial for its integration into high performance semiconductor devices. Here, we investigate the transport properties of chemical vapor deposition (CVD) grown monolayer molybdenum disulfide (MoS2) under photoexcitation using correlated scanning photocurrent microscopy and photoluminescence imaging. We examined the effect of local phase transformation underneath the metal electrodes on the generation of photocurrent across the channel length with diffraction-limited spatial resolution. While maximum photocurrent generation occurs at the Schottky contacts of semiconducting (2H-phase) MoS2, after the metallic phase transformation (1T-phase), the photocurrent peak is observed toward the center of the device channel, suggesting a strong reduction of native Schottky barriers. Analysis using the bias and position dependence of the photocurrent indicates that the Schottky barrier heights are a few millielectron volts for 1T- and ∼200 meV for 2H-contacted devices. We also demonstrate that a reduction of native Schottky barriers in a 1T device enhances the photoresponsivity by more than 1 order of magnitude, a crucial parameter in achieving high-performance optoelectronic devices. The obtained results pave a way for the fundamental understanding of intrinsic optoelectronic properties of atomically thin TMDs where ohmic contacts are necessary for achieving high-efficiency devices with low power consumption.

Original languageEnglish
Pages (from-to)840-849
Number of pages10
JournalACS nano
Issue number1
Publication statusPublished - Jan 27 2015


  • MoS
  • contact resistance
  • monolayer
  • optoelectronic
  • phase conversion
  • scanning photocurrent microscopy
  • transition-metal dichalcogenide

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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