Defect Sizing, Separation and Substrate Effects in Ion-Irradiated Monolayer 2D Materials

Abstract

Precise and scalable defect engineering of 2D nanomaterials is acutely sought-after in contemporary materials science. Here we present defect engineering in monolayer graphene and molybdenum disulfide (MoS${}_2$) by irradiation with noble gas ions at 30 keV. Two ion species of different masses were used in a gas field ion source microscope: helium (He${}^{+}$) and neon (Ne${}^{+}$). A detailed study of the introduced defect sizes and resulting inter-defect distance with escalating ion dose was performed using Raman spectroscopy. Expanding on existing models, we found that the average defect size is considerably smaller for supported than freestanding graphene and that the rate of defect production is larger. We conclude that secondary atoms from the substrate play a significant role in defect production, creating smaller defects relative to those created by the primary ion beam. Furthermore, a similar model was also applied to supported MoS${}_2$, another promising member of the 2D material family. Defect yields for both ions were obtained for MoS${}_2$, demonstrating their different interaction with the material and facilitating comparison with other irradiation conditions in the literature.

11 pages, 6 figures

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• An accurate measurement of electron beam induced displacement cross sections for single-layer graphene
• Precision Cutting and Patterning of Graphene with Helium Ions
• Structural analysis of polycrystalline graphene systems by Raman spectroscopy
• Electromechanics in MoS2 and WS2: nanotubes vs. monolayers
• Cutting and controlled modification of graphene with ion beams
• The effect of layer number and substrate on the stability of graphene under MeV proton beam irradiation
• A Comprehensive Multiphonon Spectral Analysis in MoS2
• Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation
• Optical Measurement of the Phase-Breaking Length in Graphene
• Robust valley polarization of helium ion modified atomically thin MoS${}_2$
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• Defect engineering in two-dimensional pentagonal PdTe${}_2$: Tuning electronic, optical, and magnetic properties
• Defect-Moderated Oxidative Etching of MoS2
• The optical absorption in indirect semiconductor to semimetal PtSe2 arises from direct transitions
• Raman spectroscopy of monolayer to bulk PtSe2 exfoliated crystals
• Suppression of the Shear Raman Mode in Defective Bilayer MoS2
• Synthesis and thermal stability of TMD thin films: A comprehensive XPS and Raman study