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Atomically thin transition metal dichalcogenides (TMDs), like MoS2 with high carrier mobilities and tunable electron dispersions, are unique active material candidates for next generation opto-electronic devices. Previous studies on ion irradiation show great potential applications when applied to two-dimensional (2D) materials, yet have been limited to micron size exfoliated flakes or smaller. To demonstrate the scalability of this method for industrial applications, we report the application of relatively low power (50 keV) 4He+ ion irradiation towards tuning the optoelectronic properties of an epitaxially grown continuous film of MoS2 at the wafer scale, and demonstrate that precise manipulation of atomistic defects can be achieved in TMD films using ion implanters. The effect of 4He+ ion fluence on the PL and Raman signatures of the irradiated film provides new insights into the type and concentration of defects formed in the MoS2 lattice, which are quantified through ion beam analysis. PL and Raman spectroscopy indicate that point defects are generated without causing disruption to the underlying lattice structure of the 2D films and hence, this technique can prove to be an effective way to achieve defect-mediated control over the opto-electronic properties of MoS2 and other 2D materials. [ABSTRACT FROM AUTHOR]

Understanding of phase‐stability and nanoscale structural modulation during lithiation of layer materials demand comprehensive analysis of the Li‐containing phases in the solid‐state reaction products. Conventional chemical analysis methods in the transmission electron microscope (TEM) are not ideal to detect Li in partially intercalated nanodomains because Li atoms do not remain stationary under the focused electron beam. An alternate approach combining density functional theory (DFT) modeling and multislice image simulation has been explored in the present study to analyze the intercalated structures and to detect and quantify Li from the recorded high‐resolution TEM (HRTEM) micrographs of partially intercalated phases. HRTEM micrographs from partially lithiated graphite and MoS2 show variations in the interlayer spacings, but are not usually directly interpretable. Hypothetical intercalated microstructures of graphite and MoS2 supercells have been generated using atomic‐scale simulations with systematically varying Li concentrations. The measured interplanar spacings are compared with those of experimentally recorded HRTEM micrographs from lithiated graphite and MoS2. The results confirm the coexistence of different lithiated phases at localized domains. This understanding of phase transformation and the lithium quantification provides a basis for understanding the structural accommodation of layered materials during intercalation. [ABSTRACT FROM AUTHOR]

Layered transition‐metal dichalcogenides (TMDs) have shown promise to replace carbon‐based compounds as suitable anode materials for Lithium‐ion batteries (LIBs) owing to facile intercalation and de‐intercalation of lithium (Li) during charging and discharging, respectively. While the intercalation mechanism of Li in mono‐ and bi‐layer TMDs has' been thoroughly examined, mechanistic understanding of Li intercalation‐induced phase transformation in bulk or films of TMDs is still largely unexplored. This study investigates possible scenarios during sequential Li intercalation and aims to gain a mechanistic understanding of the phase transformation in bulk MoS2 using density functional theory (DFT) calculations. The manuscript examines the role of concentration and distribution of Li‐ions on the formation of dual‐phase 2H‐1T microstructures that have been observed experimentally. The study demonstrates that lithiation would proceed in a systematic layer‐by‐layer manner wherein Li‐ions diffuse into successive interlayer spacings to render local phase transformation of the adjacent MoS2 layers from 2H‐to‐1T phase in the multilayered MoS2. This local phase transition is attributed to partial ionization of Li and charge redistribution around the metal atoms and is followed by subsequent lattice straining. In addition, the stability of single‐phase vs. multiphase intercalated microstructures, and the origins of structural changes accompanying Li‐ion insertion are investigated at atomic scales. [ABSTRACT FROM AUTHOR]

Atomically thin transition metal dichalcogenides (TMDs), like MoS 2 with high carrier mobilities and tunable electron dispersions, are unique active material candidates for next generation opto-electronic devices. Previous studies on ion irradiation show great potential applications when applied to two-dimensional (2D) materials, yet have been limited to micron size exfoliated flakes or smaller. To demonstrate the scalability of this method for industrial applications, we report the application of relatively low power (50 keV) 4 He + ion irradiation towards tuning the optoelectronic properties of an epitaxially grown continuous film of MoS 2 at the wafer scale, and demonstrate that precise manipulation of atomistic defects can be achieved in TMD films using ion implanters. The effect of 4 He + ion fluence on the PL and Raman signatures of the irradiated film provides new insights into the type and concentration of defects formed in the MoS 2 lattice, which are quantified through ion beam analysis. PL and Raman spectroscopy indicate that point defects are generated without causing disruption to the underlying lattice structure of the 2D films and hence, this technique can prove to be an effective way to achieve defect-mediated control over the opto-electronic properties of MoS 2 and other 2D materials., (Creative Commons Attribution license.)