Direct Identification of Surface Bound MoO<sub>3</sub> on Single MoS<sub>2</sub> Flakes Heated in Dry and Humid Air

Rogala, Maciej; Sokołowski, Stanisław; Ukegbu, Ugonna; Mierzwa, Aneta; Szoszkiewicz, Robert

doi:10.1002/admi.202100328

Cited by 15 publications

(20 citation statements)

References 58 publications

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“…It confirmed predictions about particularly fast oxidation along the crystalline edges [35,41,42,46]. Oxidation and oxidative etching in some instances produced visible MoO 3 deposits (in various forms) appearing on the single MoS 2 flakes/nanosheets [42,47,48] or even full MoS 2 transformation [35] into single MoO 3 crystals. The phenomenological aspects related to the MoO x formation on globally heated basal planes within the MoS 2 flakes in dry air are summarized in Figure 2.…”

Section: Phenomenological Observations Of Thermal Mos 2 Oxidation In Air and In Watersupporting

confidence: 75%

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 84%

“…Thus, one might expect different reaction mechanisms at each of these oxidation regimes. However, based on the recently published literature, we suggest that the messy-looking MoS 2 surface after its vigorous oxidation can originate from physical blockage of oxidation along particular spatial directions due to locally formed accumulations of the surface-adsorbed Mo oxides and MoO x clusters [42,47,48]. Furthermore, it has been suggested that locally observed dendritic structures, observed on the MoS 2 samples heated above 500 • C (see Figure 12e) might originate from Mo oxides forming along the directions of the largest concentrations of the initially pre-adsorbed surface oxygen [41].…”

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 87%

“…The first study discussed the coexistence of the Mo oxides onto MoS 2 flakes oxidized at high relative humidity of 80 ± 7% and at a mean temperature of only 205 • C [42]. The second study discussed a regime of low relative humidity of 9.2 ± 2.2% and heating temperature of 221 ± 8 • C [48]. In both studies, the MoO 3 layer of thickness of ca.…”

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 99%

“…Finally, very recently, direct chemical proofs for microscale presence of the MoO 3 nanoparticles and small patched on single MoS 2 flakes in air during thermal oxidative etching, particularly between 350 and 390 • C, have been provided in separate two reports (one on geological another on CVDgrown MoS 2 ) via a combination of local AFM, XPS, TEM, SEM and XAS studies [47,48]. In particular, Park et al [48] showed that such small MoO 3 nanoparticles promote oxidation on CVD-grown MoS 2 .…”

Section: Mo Oxides and Their Derivatives In Mos 2 Oxidationmentioning

confidence: 99%

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Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Szoszkiewicz

2021

Materials

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Thin and single MoS2 flakes are envisioned to contribute to the flexible nanoelectronics, particularly in sensing, optoelectronics and energy harvesting. Thus, it is important to study their stability and local surface reactivity. Their most straightforward surface reactions in this context pertain to thermally induced interactions with atmospheric oxygen. This review focuses on local and thermally induced interactions of MoS2 crystals and single MoS2 flakes. First, experimentally observed data for oxygen-mediated thermally induced morphological and chemical changes of the MoS2 crystals and single MoS2 flakes are presented. Second, state-of-the-art mechanistic insight from computer simulations and arising open questions are discussed. Finally, the properties and fate of the Mo oxides arising from thermal oxidation are reviewed, and future directions into the research of the local MoS2/MoOx interface are provided.

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Section: Phenomenological Observations Of Thermal Mos 2 Oxidation In Air and In Watersupporting

confidence: 75%

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 84%

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 87%

Section: Microscopic Oxidation Above 400 °Cmentioning

confidence: 99%

Section: Mo Oxides and Their Derivatives In Mos 2 Oxidationmentioning

confidence: 99%

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Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Szoszkiewicz

2021

Materials

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Investigation of Doping Effects on the Local Electrochemical Activity of Transition Metal Dichalcogenides 2D Materials

Silva,

Kim,

de Oliveira

et al. 2024

Adv Funct Materials

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Finding strategies to enhance catalysts’ electrochemical activity is based on controlling the material design. Bidimensional materials (2DM) such as MoS2 are explored as catalysts for the hydrogen evolution reaction (HER). A comprehensive study of the effects of doping 2D materials with transition metals based on theoretical predictions in tandem with experimental investigation correlates the doping type to the changes in the electronic and electrochemical activity. Localized electrochemical maps obtained by scanning electrochemical cell microscopy (SECCM) reveal that Ti‐doping induces a heterogeneous increase in 2H‐MoS2 basal plane electrochemical activity, while Ni‐doping induces a homogeneous decrease. Additionally, Kelvin probe microscopy provides insight into Ti‐doping, showcasing a decline in the 2H‐MoS2 work function, therefore confirming the predictions from density functional theory simulations. In essence, the findings underscore the potential of transition metal coordination on the 2H‐MoS2 surface as an attractive method for locally doping 2D materials with minimal damage to the crystalline lattice, consequently enhancing the electrochemical activity on the material's basal plane.

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Structural Stability of Bilayer MoS₂ in Ambient Air

Femi-Oyetoro

Yao

Hathaway

et al. 2021

Adv Materials Inter

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contain dendritic structures with a fractal dimension consistent with a diffusionlimited aggregation process. [3,6] Although a variety of degradation prevention techniques have been reported such as encapsulation with hexagonal boron nitride [9] and polymers, [10] use of novel gate dielectrics, [11] and placement in an environment with a desiccant [3] or in a vacuum, [4] such techniques are not applicable for ambientair applications such as gas sensors. To our knowledge, the stability of bilayer (BL) and thicker-layer MoS 2 films in ambient air has not been extensively studied. It is important to understand the stability of such films for developing applications and having a better understanding of ML degradation. In this paper, we report on the structural stability of preheated and as-grown BL and thicker-layer MoS 2 films in ambient air. The films are grown using CVD on SiO 2 substrates and studied using atomic force microscopy (AFM), and Raman and PL spectroscopies.BL and thicker-layer MoS 2 and other TMD films, nanosheets, [12] and nanostructures, [13] although having indirect band gaps, have attracted considerable interest because of their useful properties. For example, BLs and thicker-layers have higher electrical conductivities than MLs due to their higher density of states and more effective screening of impurities in the substrate. [14] In addition, BL device yield is typically higher than ML device yield, due to the greater mechanical strength of BLs. [15,16] BL and thicker-layer TMD films offer layer control of properties such as spin-orbit coupling, [17] interlayer coupling, [18] and band gap. [19] Varying the twist angle between layers in BLs has been reported to result in twist-dependent valley and band alignment, [20] and Moiré pattern excitons. [21] The ambient-air degradation of CVD-grown ML MoS 2 and other ML TMD films was first reported by Gao et al. [3] They observed that ML MoS 2 and WS 2 grown on SiO 2 substrates developed extensive cracking, morphological changes, and quenching of PL after exposure to ambient air at room temperature (RT) for a period of about a year. The degradation was attributed to oxidation along grain boundaries and other defects. It was found that water vapor in the air was necessary for degradation to occur since films did not degrade in a dry box. In addition, Budania et al. [4] reported that mechanically exfoliated thin multilayer MoS 2 flakes on SiO 2 developed speckles in air at a high relative humidity (RH) of 60% over a period of about a year. Kotsakidis et al. [5] reported

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Direct Identification of Surface Bound MoO₃ on Single MoS₂ Flakes Heated in Dry and Humid Air

Cited by 15 publications

References 58 publications

Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Investigation of Doping Effects on the Local Electrochemical Activity of Transition Metal Dichalcogenides 2D Materials

Structural Stability of Bilayer MoS₂ in Ambient Air

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Direct Identification of Surface Bound MoO3 on Single MoS2 Flakes Heated in Dry and Humid Air

Cited by 15 publications

References 58 publications

Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Local Interactions of Atmospheric Oxygen with MoS2 Crystals

Investigation of Doping Effects on the Local Electrochemical Activity of Transition Metal Dichalcogenides 2D Materials

Structural Stability of Bilayer MoS2 in Ambient Air

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Direct Identification of Surface Bound MoO₃ on Single MoS₂ Flakes Heated in Dry and Humid Air

Structural Stability of Bilayer MoS₂ in Ambient Air