Evidence of defect formation in monolayer MoS2 at ultralow accelerating voltage electron irradiation
Dash, Ajit Kumar; Swaminathan, Hariharan; Berger, Ethan; Mondal, Mainak; Lehenkari, Touko; Prasad, Pushp Raj; Watanabe, Kenji; Taniguchi, Takashi; Komsa, Hannu-Pekka; Singh, Akshay (2023-04-11)
Dash, Ajit Kumar
Swaminathan, Hariharan
Berger, Ethan
Mondal, Mainak
Lehenkari, Touko
Prasad, Pushp Raj
Watanabe, Kenji
Taniguchi, Takashi
Komsa, Hannu-Pekka
Singh, Akshay
Institute of physics publishing
11.04.2023
Dash, A. K., Swaminathan, H., Berger, E., Mondal, M., Lehenkari, T., Prasad, P. R., Watanabe, K., Taniguchi, T., Komsa, H.-P., & Singh, A. (2023). Evidence of defect formation in monolayer MoS 2 at ultralow accelerating voltage electron irradiation. 2D Materials, 10(3), 035002. https://doi.org/10.1088/2053-1583/acc7b6
https://creativecommons.org/licenses/by-nc-nd/4.0/
© Copyright 2023 IOP Publishing. This is the Accepted Manuscript version of an article accepted for publication in 2D Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/2053-1583/acc7b6. This Accepted Manuscript is available for reuse under a CC BY-NC-ND licence after the 12 month embargo period provided that all the terms of the licence are adhered to.
https://creativecommons.org/licenses/by-nc-nd/4.0/
© Copyright 2023 IOP Publishing. This is the Accepted Manuscript version of an article accepted for publication in 2D Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/2053-1583/acc7b6. This Accepted Manuscript is available for reuse under a CC BY-NC-ND licence after the 12 month embargo period provided that all the terms of the licence are adhered to.
https://creativecommons.org/licenses/by-nc-nd/4.0/
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:oulu-202401021024
https://urn.fi/URN:NBN:fi:oulu-202401021024
Tiivistelmä
Abstract
Control on spatial location and density of defects in two-dimensional materials can be achieved using electron beam irradiation. Conversely, ultralow accelerating voltages ($ \leqslant \,$5 kV) are used to measure surface morphology, with no expected defect creation. We find clear signatures of defect creation in monolayer MoS2 at these voltages. Evolution of ${\text{E}}^{{\prime}}$ and ${{\text{A}}^{{\prime}}_1}$ Raman modes with electron dose, and appearance of defect activated peaks indicate defect formation. To simulate Raman spectra of MoS2 at realistic defect distributions, while retaining density-functional theory accuracy, we combine machine-learning force fields for phonons and eigenmode projection approach for Raman tensors. Simulated spectra agree with experiments, with sulphur vacancies as suggested defects. We decouple defects, doping and carbonaceous contamination using control (hBN covered and encapsulated MoS2) samples. We observe cryogenic photoluminescence quenching and defect peaks, and find that carbonaceous contamination does not affect defect creation. These studies have applications in photonics and quantum emitters.
Control on spatial location and density of defects in two-dimensional materials can be achieved using electron beam irradiation. Conversely, ultralow accelerating voltages ($ \leqslant \,$5 kV) are used to measure surface morphology, with no expected defect creation. We find clear signatures of defect creation in monolayer MoS2 at these voltages. Evolution of ${\text{E}}^{{\prime}}$ and ${{\text{A}}^{{\prime}}_1}$ Raman modes with electron dose, and appearance of defect activated peaks indicate defect formation. To simulate Raman spectra of MoS2 at realistic defect distributions, while retaining density-functional theory accuracy, we combine machine-learning force fields for phonons and eigenmode projection approach for Raman tensors. Simulated spectra agree with experiments, with sulphur vacancies as suggested defects. We decouple defects, doping and carbonaceous contamination using control (hBN covered and encapsulated MoS2) samples. We observe cryogenic photoluminescence quenching and defect peaks, and find that carbonaceous contamination does not affect defect creation. These studies have applications in photonics and quantum emitters.
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