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  • Letter
  • Open Access

Influence of sulfur vacancies on the high frequency phonon modes of ALD-grown monolayer MoS2

Jonathan Rommelfangen and Alex Redinger

Marco Antonio Gonzalez-Angulo

Devendra Pareek and Levent Gütay

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Phys. Rev. Materials 9, L121001 – Published 19 December, 2025

DOI: https://doi.org/10.1103/kzhl-5sy6

Abstract

Precise control of defects in two-dimensional materials is crucial for their application in functional devices. Raman spectroscopy is a key technique for identifying the number of layers and strain in MoS2. Changes in the peak area ratio of the Raman active modes A1g and E2g1 measured on monolayer (ML) MoS2 have, so far, only been correlated to changes in the excitation wavelength of the laser, i.e., resonant effects. However, the role of sulfur vacancies (VS) on this peak area ratio is not well studied. In this study, we show on ALD-grown MoS2 that changes in the peak area ratio of the A1g and E2g1 Raman modes depend sensibly on the number of VS in the film. Raman measurements carried out with three different excitation wavelengths are combined with detailed x-ray photoelectron spectroscopy measurements to quantify the number of VS in the film and to study their impact on vibrational properties. VS-poor MoS2 displays a stronger A1g mode compared to the E2g1 mode, whereas the ratio is reversed in VS-rich films. We propose that this effect originates from modifications in the electronic band structure of ML MoS2. Based on this experimental work, we propose that the peak area ratio of the A1g and E2g1 modes could be used as a fingerprint for the qualitative evaluation of the S deficiency in MoS2 MLs, which could be an easy-to-apply method for the quality assessment in industrial applications.

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Phys. Rev. Materials 9, L121001– Published 19 December, 2025
  • Received 17 June 2025
  • Revised 22 August 2025
  • Accepted 4 November 2025
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