<i>In situ</i> Raman study on sulfur vacancies in monolayer MoS₂

Author(s)

Leon Daniel, Yossarian Liebsch, Charleen Lintz, Umair Javed, Osamah Kharsah, Lars Breuer, Jani Kotakoski, Marika Schleberger

Abstract

Monolayer MoS

₂ combines a direct optical bandgap with an atomically thin geometry, making it a promising platform for defect engineering. Raman studies of ion-irradiated MoS

₂ are often complicated by high ion energies, incomplete defect quantification, and uncontrolled adsorbates at defect sites. Here, we irradiate large-area monolayer MoS

₂ with low-energy (600 eV) Ar

⁺ ions in a ultrahigh vacuum chamber and perform in situ Raman spectroscopy over a range of fluences. Atomic-resolution scanning transmission electron microscopy reveals predominantly randomly distributed sulfur vacancies as the dominant defect type. With increasing fluence, Raman spectra show a downshift and broadening of the E (Formula presented) (Formula presented) mode, a slight upshift and broadening of the A (Formula presented) (Formula presented) mode, and the emergence of defect-activated features, including a prominent LA(M) mode. A controlled ambient exposure followed by remeasurement separates intrinsic defect signatures from extrinsic doping: an additional A (Formula presented) (Formula presented) upshift and linewidth narrowing indicate a modest, largely reversible p-doping contribution from weak physisorption at vacancy sites, corresponding to an apparent charge transfer of ∼0.02 e per STEM-counted vacancy. Within the sensitivity of our in situ Raman measurements, oxidation-related signatures remain negligible, and adsorbate effects largely vanish upon returning to vacuum and under laser illumination. These results establish Raman fingerprints of sulfur-vacancy ensembles in monolayer MoS

₂ and provide quantitative guidance for defect engineering and metrology under controlled vacuum conditions.

Organisation(s)

Physics of Nanostructured Materials

External organisation(s)

Universität Duisburg-Essen

Journal

2D Materials

Volume

13

No. of pages

8

ISSN

2053-1583

DOI

https://doi.org/10.1088/2053-1583/ae6b2b

Publication date

06-2026

Peer reviewed

Yes

Austrian Fields of Science 2012

205019 Material sciences, 103042 Electron microscopy

Keywords

ASJC Scopus subject areas

General Chemistry, General Materials Science, Condensed Matter Physics, Mechanics of Materials, Mechanical Engineering

Portal url

https://ucrisportal.univie.ac.at/en/publications/81c85315-0a9a-44ab-ae58-22645e2b0a50