Ion irradiation is a versatile tool to introduce controlled defects into two-dimensional (2D) MoS2on account of its unique spatial resolution and plethora of ion types and energies available. In order to fully realise the potential of this technique, a holistic understanding of ion-induced defect production in 2D MoS2crystals of different thicknesses is mandatory. X-ray photoelectron spectroscopy, electron diffraction and Raman spectroscopy show that thinner MoS2crystals are more susceptible to radiation damage caused by 225 keV Xe+ions. However, the rate of defect production in quadrilayer and bulk crystals is not significantly different under our experimental conditions. The rate at which S atoms are sputtered as a function of radiation exposure is considerably higher for monolayer MoS2, compared to bulk crystals, leading to MoO3formation. P-doping of MoS2is observed and attributed to the acceptor states introduced by vacancies and charge transfer interactions with adsorbed species. Moreover, the out-of-plane vibrational properties of irradiated MoS2crystals are shown to be strongly thickness-dependent: in mono- and bilayer MoS2, the confinement of phonons by defects results in a blueshift of the
This content will become publicly available on July 27, 2024
The investigation of twisted stacked few‐layer MoS2has revealed novel electronic, optical, and vibrational properties over an extended period. For the successful integration of twisted stacked few‐layer MoS2into a wide range of applications, it is crucial to employ a noninvasive, versatile technique for characterizing the layered architecture of these complex structures. In this work, we introduce a machine learning‐assisted low‐frequency Raman spectroscopy method to characterize the twist angle of few‐layer stacked MoS2samples. A feedforward neural network (FNN) is utilized to analyze the low‐frequency breathing mode as a function of the twist angle. Moreover, using finite difference method (FDM) and density functional theory (DFT) calculations, we show that the low‐frequency Raman spectra of MoS2are mainly influenced by the effect of the nearest and second nearest layers. A new improved linear chain model (TA‐LCM) with taking the twist angle into the consideration is developed to understand the interlayer breathing modes of stacked few‐layer MoS2. This approach can be extended to other 2D materials systems and provides an intelligent way to investigate naturally stacked and twisted interlayer interactions.
more » « less- Award ID(s):
- 1945364
- NSF-PAR ID:
- 10441883
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Raman Spectroscopy
- ISSN:
- 0377-0486
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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