Large‐Area 2D Layered MoTe<sub>2</sub> by Physical Vapor Deposition and Solid‐Phase Crystallization in a Tellurium‐Free Atmosphere

Huang, Jyun Hong; Deng, Kuang Ying; Liu, Po–Tsun; Wu, Chien Ting; Chou, Cheng Tung; Chang, Wen‐Hao; Lee, Yao Jen; Hou, Tuo‐Hung

doi:10.1002/admi.201700157

Cited by 70 publications

(63 citation statements)

References 40 publications

(70 reference statements)

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“…For example, the peak associated with the E 1g -mode is unresolved due to the higher background. The subdued intensities are due to the transparency of the sapphire substrate to laser light 31 , which is in line with the previous observations for a 2.1 nm MoTe 2 film obtained on sapphire by physical vapour deposition 36 .…”

Section: Resultssupporting

confidence: 92%

Selective phase growth and precise-layer control in MoTe2

et al. 2020

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Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe 2 system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe 2 films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, semiconducting 2H-MoTe 2 is the only product. Conversely, MoO 3 leads to the preferential growth of metallic 1T′-MoTe 2. The control over phase growth allows for simultaneous deposition of both 2H-MoTe 2 and 1T′-MoTe 2 phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1T′-MoTe 2 films down to 5 nM concentration, demonstrating surface enhanced Raman spectroscopy (SERS) with sensitivity several orders of magnitude higher than for bulk 1T′-MoTe 2 .

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Section: Resultssupporting

confidence: 92%

Selective phase growth and precise-layer control in MoTe2

et al. 2020

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“…Figure 5 shows a series of Raman maps highlighting the presence of a Te metal film next to a MoTe2 flake. Representative spectra from the Raman maps are plotted in Figure 5e displaying the characteristic Te metal peaks 28,29 at ~120 cm -1 and ~140 cm -1 as well as the 2H E2g MoTe2 and Silicon peaks. Because the p++ Si electrode is used as a universal contact, electrically connecting every flake on the substrate, we hypothesize that the Te metal film plates out of the ionic liquid and that the Te atoms potentially come from all MoTe2 flakes on the substrate and not solely from the flake in the image.…”

Section: Electrochemical Phase Change By Creation Of Te Vacanciesmentioning

confidence: 99%

Reversible Electrochemical Phase Change in Monolayer to Bulk-like MoTe₂ by Ionic Liquid Gating

et al. 2020

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Transition metal dichalcogenides (TMDs) exist in various crystal structures with semiconducting, semi-metallic, and metallic properties. The dynamic control of these phases is of immediate interest for next generation electronics such as phase change memories. Of the binary Mo and W-based TMDs, MoTe2 is attractive for electronic applications because it has the lowest energy difference (40 meV) between the semiconducting (2H) and semi-metallic (1T') phases, allowing for MoTe2 phase change by electrostatic doping. Here we report phase change between the 2H and 1T' polymorphs of MoTe2 in thicknesses ranging from the monolayer case to effective bulk (73nm) using an ionic liquid electrolyte at room temperature and in air. We find consistent evidence of a partially reversible 2H-1T' transition using in-situ Raman spectroscopy where the phase change occurs in the top-most layers of the MoTe2 flake. We find a thickness-dependent transition voltage where higher voltages are necessary to drive the phase change for thicker flakes. We also show evidence of electrochemical activity during the gating process by observation of Te metal deposition. This finding suggests the formation of Te vacancies which have been reported to lower the energy difference between the 2H and 1T' phase, potentially aiding the phase change process. Our discovery that the phase change can be achieved on the surface layer of bulk materials reveals that this electrochemical mechanism does not require isolation of a single layer and the effect may be more broadly applicable than previously thought.

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“…Currently, although many methods have been tried in the fabrication of TMDs, the CVD method is the one that is widely employed for high quality TMDs . The formation of a stable phase in TMDs is closely related with synthesis conditions, such as temperature, precursor type, ratio of precursors, and the growth procedure.…”

Section: Strategies On Triggering Phase Transition In Tmdsmentioning

confidence: 99%

Strategies on Phase Control in Transition Metal Dichalcogenides

Wang

Zhou

et al. 2018

Adv Funct Materials

114

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Transition metal dichalcogenides (TMDs) consist of dozens of ultrathin layered materials that have significantly different properties due to their varied phases, which determine the properties and application range of TMDs. Interestingly, a controllable phase transition in TMDs is achieved extensively with the use of several methods. Thus, phase control is a promising way to fully exploit the potential of TMDs. This review introduces the recent rapid development of the study of the TMD phase control, starting from the basic conception of the phase and phase transition in TMDs to the strategies for obtaining phase control. The different strategies are roughly classified into several types based on their characteristics: doping, synthesis method, strain, thermal method, and interlayer coupling. Finally, an evaluation on the prospect of the emergent strategies is provided.

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Large‐Area 2D Layered MoTe₂ by Physical Vapor Deposition and Solid‐Phase Crystallization in a Tellurium‐Free Atmosphere

Cited by 70 publications

References 40 publications

Selective phase growth and precise-layer control in MoTe2

Selective phase growth and precise-layer control in MoTe2

Reversible Electrochemical Phase Change in Monolayer to Bulk-like MoTe₂ by Ionic Liquid Gating

Strategies on Phase Control in Transition Metal Dichalcogenides

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Large‐Area 2D Layered MoTe2 by Physical Vapor Deposition and Solid‐Phase Crystallization in a Tellurium‐Free Atmosphere

Cited by 70 publications

References 40 publications

Selective phase growth and precise-layer control in MoTe2

Selective phase growth and precise-layer control in MoTe2

Reversible Electrochemical Phase Change in Monolayer to Bulk-like MoTe2 by Ionic Liquid Gating

Strategies on Phase Control in Transition Metal Dichalcogenides

Contact Info

Product

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Large‐Area 2D Layered MoTe₂ by Physical Vapor Deposition and Solid‐Phase Crystallization in a Tellurium‐Free Atmosphere

Reversible Electrochemical Phase Change in Monolayer to Bulk-like MoTe₂ by Ionic Liquid Gating