Spatially Resolved Persistent Photoconductivity in MoS2-WS2 Lateral Heterostructures

Samuel Berweger, Hanyu Zhang, Prasana K. Sahoo, Benjamin M. Kupp, Jeffrey L. Blackburn, Elisa M. Miller, Thomas M. Wallis, Dmitri V. Voronine, Pavel Kabos, Sanjini U. Nanayakkara

Research output: Contribution to journalArticlepeer-review

37 Scopus Citations

Abstract

The optical and electronic properties of 2D semiconductors are intrinsically linked via the strong interactions between optically excited bound species and free carriers. Here we use near-field scanning microwave microscopy (SMM) to image spatial variations in photoconductivity in MoS2−WS2 lateral multijunction heterostructures using photon energy-resolved narrowband illumination. We find that the onset of photoconductivity in individual domains corresponds to the optical absorption onset, confirming that the tightly bound excitons in transition metal dichalcogenides can nonetheless dissociate into free carriers. These photogenerated carriers are most likely n-type and are seen to persist for up to days. Informed by finite element modeling we reveal that they can increase the carrier density by up to 200 times. This persistent photoconductivity appears to be dominated by contributions from the multilayer MoS2 domains, and we attribute the flake-wide response in part to charge transfer across the heterointerface. Spatial correlation of our SMM imaging with photoluminescence (PL) mapping confirms the strong link between PL peak emission photon energy, PL intensity, and the local accumulated charge. This work reveals the spatially and temporally complex optoelectronic response of these systems and cautions that properties measured during or after illumination may not reflect the true dark state of these materials but rather a metastable charged state.

Original languageAmerican English
Pages (from-to)14080-14090
Number of pages11
JournalACS Nano
Volume14
Issue number10
DOIs
StatePublished - 27 Oct 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2020 American Chemical Society

NREL Publication Number

  • NREL/JA-5K00-76197

Keywords

  • Heterostructure
  • Persistent photoconductivity
  • Photoluminescence
  • Scanning microwave impedance microscopy (smim)
  • Scanning microwave microscopy (smm)
  • Transition metal dichalcogenide

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