Tunable large-area phase reversion in chemical vapor deposited few-layer MoTe<sub>2</sub> films

Zhu, Xukun; Li, Aolin; Wu, Di; Zhu, Peng; Xiang, Haiyan; Liu, Song; Sun, Jian; Ouyang, Fangping; Zhou, Yu; Xiong, Xiang

doi:10.1039/c9tc03216a

Cited by 15 publications

(18 citation statements)

References 30 publications

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“…In contrast, previous studies have reported that CVD grown heterophase MoTe 2 has crystalline 2H and 1T’ phases with well‐defined, reliable heterophase boundaries with stable covalent atomic bonds. [ 20–22 ] A schematic picture of the atomically defined heterophase interface in MoTe 2 with a boundary width of less than 0.5 nm is shown in Figure a. We expect that the area ratio of the 1D heterophase boundary to the open region for local HER will be extremely small (less than 10 –4 ).…”

Section: Phase Morphology Controllable Mote2 Growthmentioning

confidence: 99%

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Lee

Ling

Kim

et al. 2021

Adv Funct Materials

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The phase engineering of transition metal dichalcogenides (TMDs) is considered a promising strategy for promoting efficient catalysis, such as the hydrogen evolution reaction (HER). While theoretical studies predict the presence of catalytically active atomic sites at heterophase boundaries in TMDs, conventional bulk HER measurements are not able to precisely explore these 1D heterophase regions for HER. Here, one reports on active HER occurring at heterophase boundaries between the semiconducting 2H and metallic 1T’ phases in large‐scale MoTe2 grown via chemical vapor deposition. Microreactors are used to investigate the local HER at varying lengths of 1D heterophase boundaries, and the results are systematically compared with the HER performance at the pristine basal planes of MoTe2. Despite the small area ratio between the 1D heterophase boundary and the open region for local HER, a clear improvement in HER is observed with a turnover frequency of 317 s–1. The Kelvin probe force microscopy determines a surface potential difference of 50 mV across the heterophase boundary, which supports sharp band bending and local charge accumulation as the basis for the TMDs’ efficient electrochemical catalysis.

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Section: Phase Morphology Controllable Mote2 Growthmentioning

confidence: 99%

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Lee

Ling

Kim

et al. 2021

Adv Funct Materials

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“…[28][29][30][31][32][33][34][35][36][37][38][39] For example, the synthesis of MoTe 2 monolayer in 1T' or 2H phase can be selected during the chemical-vapordeposition (CVD), and the 1T' to 2H phase transition of MoTe 2 monolayer can be controlled by annealing, ionic liquid gating or pressure. [6,34,38,40] On the other hand, 1T'-WSe 2 possesses a large positive bandgap around 130 meV, [4,7] which is crucial to realize QSH effect with long decoherence length at higher temperature. Recently, monolayer 1T'-WSe 2 has been successfully grown on the bilayer graphene (BLG) substrate using molecular beam epitaxy (MBE).…”

Section: Doi: 101002/adma202004930mentioning

confidence: 99%

Epitaxial Growth of Single‐Phase 1T'‐WSe₂ Monolayer with Assistance of Enhanced Interface Interaction

Chen

Zong

et al. 2020

Advanced Materials

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The WSe2 monolayer in 1T’ phase is reported to be a large‐gap quantum spin Hall insulator, but is thermodynamically metastable and so far the fabricated samples have always been in the mixed phase of 1T’ and 2H, which has become a bottleneck for further exploration and potential applications of the nontrivial topological properties. Based on first‐principle calculations in this work, it is found that the 1T’ phase could be more stable than 2H phase with enhanced interface interactions. Inspired by this discovery, SrTiO3 (100) is chosen as substrate and WSe2 monolayer is successfully grown in a 100% single 1T’ phase using the molecular beam epitaxial method. Combining in situ scanning tunneling microscopy and angle‐resolved photoemission spectroscopy measurements, it is found that the in‐plane compressive strain in the interface drives the 1T'‐WSe2 into a semimetallic phase. Besides providing a new material platform for topological states, the results show that the interface interaction is a new approach to control both the structure phase stability and the topological band structures of transition metal dichalcogenides.

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“…[ 3–5 ] The most exciting aspect of MoTe 2 is the reversible phase transition between semiconducting 2 H phase and metallic 1 T phase, which can be employed to realize high quality Ohmic contact for MoTe 2 FETs. [ 6–9 ] Albeit this merit, a large variation in the performance of pristine MoTe 2 FETs is noticed in the previously reported MoTe 2 FETs. For instance, unipolar n ‐type, p ‐type, as well as ambipolar characteristics were measured in the MoTe 2 FETs, which are irrelevant to the work functions of the contact metals.…”

Section: Introductionmentioning

confidence: 96%

Charge Density Depinning in Defective MoTe₂ Transistor by Oxygen Intercalation

Liu

Wang

et al. 2020

Adv Funct Materials

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Molybdenum ditelluride is prone to various defects. Among them, tellurium vacancies lead to the significant reduction of band gap as revealed by density functional theory (DFT) calculations. They are responsible for inducing spatial band structure variation and localized charge puddles in MoTe 2. As a result, undesirable charge density pinning is anticipated in the channel-dominated MoTe 2 field-effect transistors (FETs) even with much improved ohmic contacts, resulting in poor device characteristics, for example, conductivity minimum point (CMP) pinning and weak gate tunability. DFT simulations suggest occupying tellurium vacancies with oxygen can effectively restore MoTe 2 to its intrinsic properties and therefore remove charge density pinning. Experimentally, this can be realized by oxygen intercalation during low-pressure annealing without bringing in additional defects to MoTe 2. The CMP is unpinned in the FETs made of annealed MoTe 2 , which can be tuned by changing the contact metals with varied work functions. Moreover, much improved device characteristics, for example, a high hole current density exceeding 20 μAμm −1 , a record high hole mobility of 77 cm 2 V −1 s −1 , are obtained.

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Tunable large-area phase reversion in chemical vapor deposited few-layer MoTe₂ films

Abstract: A local large-scale reversible phase transition of MoTe2 film was accomplished through the heat treatment.

Cited by 15 publications

References 30 publications

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Epitaxial Growth of Single‐Phase 1T'‐WSe₂ Monolayer with Assistance of Enhanced Interface Interaction

Charge Density Depinning in Defective MoTe₂ Transistor by Oxygen Intercalation

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Tunable large-area phase reversion in chemical vapor deposited few-layer MoTe2 films

Abstract: A local large-scale reversible phase transition of MoTe2 film was accomplished through the heat treatment.

Cited by 15 publications

References 30 publications

Heterophase Boundary for Active Hydrogen Evolution in MoTe2

Heterophase Boundary for Active Hydrogen Evolution in MoTe2

Epitaxial Growth of Single‐Phase 1T'‐WSe2 Monolayer with Assistance of Enhanced Interface Interaction

Charge Density Depinning in Defective MoTe2 Transistor by Oxygen Intercalation

Contact Info

Product

Resources

About

Tunable large-area phase reversion in chemical vapor deposited few-layer MoTe₂ films

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Heterophase Boundary for Active Hydrogen Evolution in MoTe₂

Epitaxial Growth of Single‐Phase 1T'‐WSe₂ Monolayer with Assistance of Enhanced Interface Interaction

Charge Density Depinning in Defective MoTe₂ Transistor by Oxygen Intercalation